Table of Contents
*****************
GNU Recutils
1 Introduction
2 A Little Example
3 Fields and Records
4 Comments
5 Record Descriptors
6 %rec
7 %mandatory and %prohibit
8 %unique and %key
9 %doc
10 %typedef and %type
10.1 Declaring types
10.2 Types and fields
10.3 Escalar types
10.4 String types
10.5 Enumerated types
10.6 Time related types
10.7 Other types
11 %auto
12 %sort
13 %size
14 %confidential
15 Compound Field Names
16 Date input formats
16.1 General date syntax
16.2 Calendar date items
16.3 Time of day items
16.4 Time zone items
16.5 Combined date and time of day items
16.6 Day of week items
16.7 Relative items in date strings
16.8 Pure numbers in date strings
16.9 Seconds since the Epoch
16.10 Specifying time zone rules
16.11 Authors of `parse_datetime'
17 Regular Expressions
18 Common Options
18.1 Selection Expressions
18.1.1 Operands
18.1.1.1 Numeric Literals
18.1.1.2 String Literals
18.1.1.3 Field Values
18.1.1.4 Parenthesized Expressions
18.1.2 Operators
18.1.2.1 Arithmetic Operators
18.1.2.2 Boolean Operators
18.1.2.3 Comparison Operators
18.1.2.4 Date Comparison Operators
18.1.2.5 Field Operators
18.1.2.6 String Operators
18.1.2.7 Conditional Operator
18.1.3 Evaluation of Selection Expressions
18.2 Field Expressions
19 recinf
19.1 recinf Invocation
20 recsel
20.1 recsel Invocation
20.2 recsel Examples
20.3 recsel Encryption
21 recins
21.1 recins Invocation
21.2 recins Examples
21.3 recins Encryption
22 recdel
22.1 recdel Invocation
22.2 recdel Examples
23 recset
23.1 recset Invocation
23.2 recset Examples
24 recfix
24.1 recfix Invocation
24.2 recfix Examples
25 recfmt
25.1 recfmt Invocation
25.2 recfmt Templates
25.3 recfmt Examples
26 csv2rec
26.1 csv2rec Invocation
26.2 csv2rec Examples
27 rec2csv
27.1 rec2csv Invocation
27.2 rec2csv Conversion
27.3 rec2csv Examples
28 mdb2rec
28.1 mdb2rec Invocation
28.2 mdb2rec Examples
Appendix A GNU Free Documentation License
GNU Recutils
************
This manual documents version 1.5 of the GNU recutils.
This manual is for GNU recutils (version 1.5, 10 January 2012).
Copyright (C) 2009, 2010, 2011, 2012 Jose E. Marchesi
Copyright (C) 1994-2012 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
Version 1.3 or any later version published by the Free Software
Foundation; with no Invariant Sections, no Front-Cover Texts, and
no Back-Cover Texts. A copy of the license is included in the
section entitled "GNU Free Documentation License".
1 Introduction
**************
GNU recutils is a set of tools and libraries to access human-editable,
text-based databases called _recfiles_. The data is stored as a
sequence of records, each record containing an arbitrary number of
named fields. Advanced capabilities usually found in other data
storage systems are supported: data types, data integrity (keys,
mandatory fields, etc) as well as the ability of records to refer to
other records (sort of foreign keys). Despite its simplicity, recfiles
can be used to store medium-sized databases.
So, yet another data storage system? The mere existence of this
package deserves an explanation. There is a rich set of already
available free data storage systems, covering a broad range of
requirements. Big systems having complex data storage requirements
will probably make use of some full-fledged relational system such as
MySQL or PostgreSQL. Less demanding applications, or applications with
special deployment requirements, may find it more convenient to use a
simpler system such as SQLite, where the data is stored in a single
binary file. XML files are often used to store configuration settings
for programs, and to encode data to be transmitted through networks.
So it looks like all the needs are covered by the existing
solutions... but consider the following characteristics of the data
storage systems mentioned in the previous paragraph:
-The stored data is not directly readable by humans.
-The stored data is definitely not directly writable by humans.
-They are program dependent.
-They are not easily managed by version control systems.
Regarding the first point (human readability), while it is clearly
true for the binary files, some may argue XML files are indeed human
readable... well... try to r&iamp;ead
this
. YAML (1) is an example of a hierarchical data
storage format which is much more readable than XML. The problem with
YAML is that it was designed as a "data serialization language" and
thus to map the data constructs usually found in programming languages.
That makes it too complex for the simple task of storing plain lists of
items.
Recfiles are human-readable, human-writable and still they are easy
to parse and to manipulate automatically. Obviously they are not
suitable for any task (for example, it can be difficult to manage
hierarchies in recfiles) and performance is somewhat sacrificed in
favor of readability. But they are quite handy to store small to
medium simple databases.
The GNU recutils suite comprises:
- This texinfo manual, describing the Rec format and the
accompanying software.
- A C library (librec) that provides a rich set of functions to
manipulate rec data.
- A set of C utilities (recinf, recsel, recins, recdel, recset and
recfix) that can be used in shell scripts and in the command line
to operate on rec files.
- An emacs mode, `rec-mode'.
---------- Footnotes ----------
(1) Yet Another Markup Language
2 A Little Example
******************
Everyone loves to grow a nice book collection at home. Unfortunately,
in most cases the management of our private books gets uncontrolled:
some books get lost, some of them may be loaned to some friend, there
are some duplicated (or even triplicated!) titles because we forgot
about the existence of the previous copy, and many more details.
In order to improve the management of our little book collection we
could make use of a complex data storage system such as a relational
database. The problem with that approach, as explained in the previous
section, is that the tool is too complicated for the simple task: we do
not need the full power of a relational database system to maintain a
simple collection of books.
With GNU recutils it is possible to maintain such a little database
in a text file. Let's call it `books.rec'. The following table
resumes the information items that we want to store for each title,
along with some common-sense restrictions.
- Every book has a title, even if it is "No Title".
- A book can have several titles.
- A book can have more than one author.
- Sometimes the author is not known.
- Sometimes we don't care about who the author of a book is.
- We usually store our books at home.
- We use to loan books to friends.
- On occasions we loose track to the physical location of a book.
Did we loan it to anyone? Was it lost in the last move? Is it in
some hidden place at home?
The contents of the rec file follows:
# -*- mode: rec -*-
%rec: Book
%mandatory: Title
%type: Location enum loaned home unknown
%doc:
+ A book in my personal collection.
Title: GNU Emacs Manual
Author: Richard M. Stallman
Publisher: FSF
Location: home
Title: The Colour of Magic
Author: Terry Pratchett
Location: loaned
Title: Mio Cid
Author: Anonymous
Location: home
Title: chapters.gnu.org administration guide
Author: Nacho Gonzalez
Author: Jose E. Marchesi
Location: unknown
Title: Yeelong User Manual
Location: home
# End of books.rec
Simple. The file contains a set of records separated by blank lines.
Each record is composed by a set of fields with a name and a value.
The GNU recutils can then be used to access the contents of the file.
For example, we could get a list of the names of loaned books invoking
`recsel' in the following way:
$ recsel -e "Location = 'loaned'" -P Title books.rec
The Colour of Magic
3 Fields and Records
********************
A "field" is the written form of an association between a label and a
value. For example, if we wanted to associate the label `Name' with
the value `Ada Lovelace' we would write:
Name: Ada Lovelace
The separator between the field name and the field value is a colon
followed by a blank character (space and tabs, but not newlines). The
name of the field shall begin in the first column of the line.
A "field name" is a sequence of alphanumeric characters plus dashes
(`-') and underscores (`_'), starting with a letter or the character
`%'. The regular expression denoting a field name is:
[a-zA-Z%][a-zA-Z0-9_-]+
Field names are case-sensitive. `Foo' and `foo' are considered
different field names.
The following list contains valid field names (the final colon is not
part of the names):
Foo:
foo:
A23:
ab1:
A_Field:
The "value of a field" is a sequence of characters terminated by a
single newline character (`\n').
Sometimes a value is too long to fit in the usual width of terminals
and screens. In that case, depending on the specific tool used to
access the file, the readability of the data would not be that good.
It is therefore possible to physically split a logical line by escaping
a newline with a backslash character, as in:
LongLine: This is a quite long value \
composed by a unique logical line \
split in several physical lines.
The sequence `\n' (newline) `+' (PLUS) and an optional `_' (SPACE)
is interpreted as a newline when found in a field value. For example,
the C string `"bar1\nbar2\n bar3"' would be encoded in the following
way in a field value:
Foo: bar1
+ bar2
+ bar3
A "record" is a group of one or more fields written one after the
other:
Name1: Value1
Name2: Value2
Name2: Value3
It is possible for several fields in a record to share the same name
or/and the field value. The following is a valid record containing
three fields:
Name: John Smith
Email: john.smith@foomail.com
Email: john@smith.name
The "size of a record" is defined as the number of fields that it
contains. There is no such like an empty record, so the minimum size
for a record is 1. The maximum number of fields for a record is only
limited by the available physical resources. The size of the previous
record is 3.
Records are separated by one or more blank lines. For instance, the
following example shows a file named `personalities.rec' featuring
three records:
Name: Ada Lovelace
Age: 36
Name: Peter the Great
Age: 53
Name: Matusalem
Age: 969
4 Comments
**********
Any line having an `#' (ASCII 0x23) character in the first column is a
comment line.
Comment lines are quite useful to insert additional information that
is not part of the database but useful otherwise.
It is also quite convenient to comment-out information from the
recfile without having to remove it in a definitive way: you may want
to recover the data into the database later! Comment lines can be used
to comment-out both full registers and single fields:
Name: Jose E. Marchesi
# Occupation: Software Engineer
# Severe lack of brain capacity
# Fired on 02/01/2009 (without compensation)
Occupation: Unoccupied
Comments are also useful for headers, footers, comment blocks and all
kind of markers:
# -*- mode: rec -*-
#
# TODO
#
# This file contains the Bugs database of GNU recutils.
#
# Blah blah...
...
# End of TODO
5 Record Descriptors
********************
Certain properties of a set of records can be specified by preceding
them with a "record descriptor". A record descriptor is itself a
record, and uses fields with some predefined names to store the
properties. The most basic property that can be specified for a set of
records is their "type". The special field name `%rec' is used for
that purpose:
%rec: Entry
Id: 1
Name: Entry 1
Id: 2
Name: Entry 2
The records following the descriptors are then identified as having
its type. So in the example above we would say there are two records
of type "Entry".
The effect of a record descriptor ends when another descriptor is
found in the stream of records. This allows to store different kind of
records in the same database. For example, consider you have to
maintain a depot. You will need to keep records of both the current
stockage and the movements.
The following example shows the usage of two record descriptors to
store both kind of records: articles and movements.
%rec: Article
Id: 1
Title: Article 1
Id: 2
Title: Article 2
%rec: Movement
Id: 1
Type: sell
Date: 20 April 2011
Id: 2
Type: adquisition
Date: 21 April 2011
Besides determining the type of the records that follows in the
stream, record descriptors can be used to describe other properties of
those records. That can be done by using the so-called "special
fields", having special names from a predefined set. Consider for
example the following database, where the descriptor is used to specify
a primary key and a mandatory field:
%rec: Item
%key: Id
%mandatory: Title
Id: 10
Title: Notebook (big)
Id: 11
Title: Fountain Pen
Note that the names of special fields always start with the character
`%'. Also note that it is also possible to use non-special fields in a
record descriptor, but such fields will have no effect on the described
record set.
What follows is an exhaustive list of the supported special fields.
They are discussed in deep in the following sections.
`%rec'
Used to name the type of a set of records and to mark record
descriptors.
`%mandatory'
`%prohibit'
Those special fields are used to control which fields can and
cannot be included in records.
`%unique'
`%key'
Used to specify unique fields and primary keys.
`%auto'
Used to automatically generate certain fields when creating new
records, like auto counter and time-stamps.
`%doc'
Used to describe the contents of a record set.
`%typedef'
`%type'
Used to define named types and to associated types with fields.
`%sort'
Used to keep your records sorted by some given field.
`%size'
Used to control the dimensions of a record set.
`%confidential'
Used to store confidential information.
6 %rec
******
The `%rec' special field is used for two main purposes: to identify a
record as a record descriptor, and to provide a name for the described
record set. The synopsis of the usage of the field is the following:
%rec: TYPE [URL_OR_FILE]
TYPE is the name of the kind of records described by the descriptor.
It is mandatory to specify it, and it follows the same lexical
conventions used by field names. *Note Fields and Records::. There is
a non-enforced convention to use singular nouns, because the name makes
reference to the type of a single entity, even if it applies to all the
records contained in the record set. For example, the following record
set contains transactions, and the type specified in the record
descriptor is `Transaction'.
%rec: Transaction
Id: 10
Title: House rent
Id: 11
Title: Loan
Only one `%rec' field shall appear in a record descriptor. If there
are more it is considered an integrity violation. It is highly
recommended (but not enforced) to place this field in the first
position of the record descriptor.
Sometimes it is convenient to store records of the same type in
different files. The duplication of record descriptors in this case
would surely lead to consistency problems. A possible solution would
be to keep the record descriptor in a separated file and then include
it in any operation by using pipes. For example:
$ cat descriptor.rec data.rec | recsel ...
For those cases it is more convenient to use a "external descriptor".
External descriptors can be built appending a file path to the `%rec'
field value, like:
%rec: FSD_Entry /path/to/file.rec
The previous example indicates that a record descriptor describing
the `FSD_Entry' records shall be read from the file
`/path/to/file.rec'. A record descriptor for `FSD_Entry' may not exist
in the external file. Both relative and absolute paths can be
specified there.
URLs can be used as sources for external descriptors as well. In that
case we talk about "remote descriptors". For example:
%rec: Department http://www.myorg.com/Org.rec
The URL shall point to a text file containing rec data. If there is a
record descriptor in the remote file documenting the `Department' type,
it will be used.
Note that the local record descriptor can provide additional fields
to "expand" the record type. For example:
%rec: FSD_Entry http://www.jemarch.net/downloads/FSD.rec
%mandatory: Rating
The record descriptor above is including the contents of the
`FSD_Entry' record descriptor from the URL, and adding them to the
local record descriptor, that in this case contains just the
`%mandatory' field.
If you are using the GNU recutils to process your recfiles, any URL
schema supported by `libcurl' will work.
7 %mandatory and %prohibit
**************************
Those special field names are used to restrict the fields that can
appear in the records stored in a database. Their usage is:
%mandatory: FIELD1 FIELD2 ... FIELDN
%prohibit: FIELD1 FIELD2 ... FIELDN
In both cases the list of field names are separated by one or more
blank characters.
The fields listed in some `%mandatory' entry will be considered
mandatory; i.e., at least one field with this name shall be present in
any record of this kind. Records violating this restriction will be
considered invalid and a checking tool will report the situation as a
data integrity failure.
Consider for example an "addressbook" database where each record
stores the information associated with a contact. The records will be
heterogeneous, in the sense they won't feature exactly the same fields:
the contact of an internet shop will probably have an `Url' field,
while the entry for our grandmother probably wont. We still want to
make sure that every entry has at a field: the name of the contact. In
that case we could use `%mandatory' as follows:
%rec: Contact
%mandatory: Name
Name: Granny
Phone: +12 23456677
Name: Yoyodyne Corp.
Email: sales@yoyod.com
Phone: +98 43434433
Similarly, the fields listed in some `%prohibit' entry will be
considered forbidden; i.e., no field with this name shall be present in
any record of this kind. Again, records violating this restriction
will be considered invalid.
This can be useful when some field name is reserved for some future
use. For example, if we want to make sure no `Telex' will be even used
in our contacts database, we would change the record descriptor as
follows:
%rec: Contact
%mandatory: Name
%prohibit: Telex
Several `%mandatory' and/or `%prohibit' fields can appear in the same
record descriptor. The set of mandatory or prohibited fields is the
union of all the entries. For example, in the following database both
`Id' and `id' are prohibited:
%rec: Entry
%prohibit: Id
%prohibit: id
8 %unique and %key
******************
These special field names are used to avoid several instances of the
same field in a record, and to implement keys in record sets. Their
usage is:
%unique: FIELD1 FIELD2 ... FIELDN
%key: FIELD
The list of field names are separated by one or more blank characters.
The `%unique' special field allows to declare fields as unique,
meaning there cannot exist more than one field with the same name in a
single record.
For example, an entry in an addressbook database could contain an
`Age' field. It does not make sense for a single person to be of
several ages, so that field could be declared as "unique" in the
corresponding record descriptor as follows:
%rec: Contact
%mandatory: Name
%unique: Age
Several `%unique' fields can appear in the same record descriptor. The
set of unique fields is the union of all the entries.
`%key' makes the referred field the primary key of the record set.
Its effect is that any field with that name must be both unique and
mandatory, and additionally the values of those fields shall be unique
in the context of the record set. This closely corresponds to the
notion of "primary key" usually implemented in the relational systems.
Consider for example a database of items in a stockage. Each item is
idenfitied by a numerical `Id' field. No item may have more than one
`Id', and no items may exist without an associated `Id'. Additionally,
no two items may share the same `Id'. This common situation can be
implementing by declaring `Id' as the key in the record descriptor:
%rec: Item
%key: Id
%mandatory: Title
Id: 1
Title: Box
Id: 2
Title: Sticker big
It would not make sense to have several primary keys in a record set,
and thus it is not allowed to have several `%key' fields in the same
record descriptor. That situation is considered a data integrity
violation and will be reported by a checking tool.
9 %doc
******
This field contains documentation about the record.
It is like a comment, but this field can be managed in a programmatic
way easier.
10 %typedef and %type
*********************
Field values are, by default, unrestricted text strings. However, it
is often useful to impose some restrictions on the values of certain
fields. For example, consider the following record:
Id: 111
Name: Jose E. Marchesi
Age: 30
MaritalStatus: single
Phone: +49 666 666 66
Where `Id' is a numeric identifier for a person. `Name' will never
use several lines. `Age' will tipically be in the range `0..120', and
there are only a few valid values for `MaritalStatus': single, married
and widow. Phones may be restricted to some standard format as well to
be valid. All those restrictions (and many others) can be enforced by
using "field types".
There are two kind of field types: anonymous and named. Those are
described in the following subsections.
10.1 Declaring types
====================
A type can be declared in a record descriptor by using the `%typedef'
special field. The syntax is:
%typedef: TYPE_NAME TYPE_DESCRIPTION
Where TYPE_NAME is the name of the new type, and TYPE_DESCRIPTION a
description which varies depending of the kind of type. For example,
this is how a type `Age_t' could be defined as numbers in the range
`0..120':
%typedef: Age_t range 0 120
Type names are identifiers having the following syntax:
[a-zA-Z][a-zA-Z0-9_-]*
Even though any identifier with that syntax could be used for types, it
is a good idea to consistently follow some convention to help
distinguishing type names from field names. For example, the `_t'
suffix could be used for types.
A type can be declared to be a synonym of another type. The syntax
is:
%typedef: TYPE_NAME OTHER_TYPE_NAME
Where TYPE_NAME is declared to be a synonym of OTHER_TYPE_NAME. This
is useful to avoid duplicated type descriptions. For example, consider
the following example:
%typedef: Id_t int
%typedef: Item_t Id_t
%typedef: Transaction_t Id_t
Both `Item_t' and `Transaction_t' are synonyms for the type `Id_t'.
They are both numeric identifiers.
The order of the `%typedef' fields is not relevant. In particular,
a type definition can reference other type that is defined below. The
previous example could have been written as:
%typedef: Item_t Id_t
%typedef: Transaction_t Id_t
%typedef: Id_t int
Integrity checks will complain if undefined types are referenced, and
if there are loops (direct or indirect) in type declarations. For
example, the following set of declarations contains a loop and are thus
invalid:
%typedef: A_t B_t
%typedef: B_t C_t
%typedef: C_t A_t
The scope of a type is the record descriptor where it is defined.
10.2 Types and fields
=====================
Fields can be declared to have a given type by using the `%type'
special field in a record descriptor. The synopsis is:
%type: FIELD_LIST TYPE_NAME_OR_DESCRIPTION
Where FIELD_LIST is a list of field names separated by commas.
TYPE_NAME_OR_DESCRIPTION can be either a type name declared with
`%typedef', or a type description. Type names are useful when several
fields are declared to be of the same type:
%typedef: Id_t int
%type: Id Id_t
%type: Product Id_t
Anonymous types can be used by writing a type description instead of a
type name. They help to avoid superfluous type declarations. A record
containing a single Id field, for example, can be defined without
having to use a `%typedef' in the following way:
%rec: Task
%type: Id int
10.3 Escalar types
==================
The rec format supports the declaration of fields of the following
escalar types: integer numbers, ranges and reals.
Signed "integers" are supported by using the `integer' declaration:
%typedef: Id_t int
Given that declaration, Fields of type `Id_t' must contain integers,
that may be negative. Hexadecimal values can be written using the `0x'
prefix, and octal values use an extra `0'. Valid examples are:
%type: Id Id_t
Id: 100
Id: -23
Id: -0xFF
Id: 020
Sometimes it is desirable to reduce the "range" of integers allowed in a
field. That can be achieved by using a range type declaration:
%typedef: Percentage_t range 0 100
Note that it is possible to omit the minimum index in ranges. In that
case it is implicitly zero:
%typedef: Percentage_t range 100
Hexadecimal and octal numbers can be used to specify the limits in a
range. This helps to define scalar types whose natural base is not
ten, like for example:
%typedef: Address_t range 0x0000 0xFFFF
%typedef: Perms_t range 755
"Real" fields can be declared with the `real' type specifier. A wide
range of real numbers can be represented this way, only limited by the
underlying floating point representation. For example:
%typedef: Longitude_t real
Examples of fields of type real:
%rec: Rectangle
%typedef: Longitude_t real
%type: Width Longitude_t
%type: Height Longitude_t
Width: 25.01
Height: 10
10.4 String types
=================
The `line' field type specifier can be used to restrict the value of a
field to a single line, i.e. no newline characters are allowed. For
example, a type for proper names could be declared as:
%typedef: Name_t line
Examples of fields of type line:
Name: Mr. Foo Bar
Name: Mss. Bar Baz
Name: This is
+ invalid
Sometimes it is the maximum size of the field value that shall be
restricted. The `size' field type specifier can be used to define the
maximum number of characters a field value can have. For example, if
we were collecting input that will get written in a paper-based forms
system allowing up to 25 characters width entries, we could declare the
entries as:
%typedef: Address_t size 25
Note that hexadecimal and octal integer constants can also be used to
specify field sizes:
%typedef: Address_t size 0x18
Arbitrary restrictions can be defined by using regular expressions.
The "regexp" field type specifier introduces an ERE (extended regular
expression) that will be matched against fields having that name. The
synopsis is:
%typedef: TYPE_NAME regexp /RE/
For example, consider the `Id_t' type designed to represent the
encoding of the identifier of ID cards in some country:
%typedef: Id_t regexp /[0-9]{9}[a-zA-Z]/
Examples of fields of type `Id_t' are:
IDCard: 123456789Z
IDCard: invalid id card
Note that the slashes delimiting the `RE' can be replaced with any
other character that is not itself used as part of the regexp. That is
useful in some cases such as:
%typedef: Path_t regexp |(/[^/]/?)+|
The regexp flavor supported in recfiles are the POSIX EREs plus several
GNU extensions. *Note Regular Expressions::.
10.5 Enumerated types
=====================
Fields of this type contain symbols taken from an enumeration.
The type is described by writing the sequence of symbols conforming
the enumeration. Enumeration symbols are strings described by the
following regexp:
[a-zA-Z0-9][a-zA-Z0-9_-]*
The symbols are separated by blank characters (including newlines).
For example:
%typedef: Status_t enum NEW STARTED DONE CLOSED
%typedef: Day_t enum Monday Tuesday Wednesday Thursday Friday
+ Saturday Sunday
It is possible to insert comments when describing an enum type. The
comments are delimited by parenthesis pairs. The contents of the
comments can be any character but parenthesis. For example:
%typedef: TaskStatus_t enum
+ NEW (The task was just created)
+ IN_PROGRESS (Task started)
+ CLOSED (Task closed)
"Boolean" fields can be seen as special enumerations holding the binary
values.
%typedef: Yesno_t bool
The literals allowed in boolean fields are `yes/no', `0/1' and
`true/false'. Examples are:
SwitchedOn: 1
SwitchedOn: yes
SwitchedOn: false
10.6 Time related types
=======================
The "Date" field type specifier can be used to declare dates and times.
The synopsis is:
%typedef: TYPE_NAME date
The several date/time syntax supported by librec is provided by the
`date' module from gnulib. *Note Date input formats::.
10.7 Other types
================
The "Email" field type specifier is used to declare electronic
addresses such as emails. The synopsis is:
%typedef: Email_t email
Sometimes it is useful to make fields to store field names. For that
purpose the "Field" field type specifier is supported. The synopsis is:
%typedef: Field_t field
11 %auto
********
This special field allows to include auto-generated fields in our
databases. Its usage is:
%auto: FIELD1 FIELD2 ... FIELDN
The list of field names are separated by one or more blank characters.
There can be several `%auto' fields in the same record descriptor, the
effective list of auto-generated fields being the union of all the
entries.
Auto generated fields are a very useful facility usually providen by
database implementations. Consider for example a list of articles in
stock in a toys store:
%rec: Item
%key: Description
Description: 2cm metal soldier WWII
Amount: 2111
Description: Flying Helicopter Indoor Maxi
Amount: 8
...
It would be natural to identify the items by its description, but it
is also error prone: was it "Flying Helicopter Indoor Maxi" or "Flying
Helicopter Maxi Indoor"? Was "Helicopter" in lower case or upper case?
It is quite common in databases to use some kind of numeric "Id" to
uniquely identify items like those ones. That is because numbers are
easy to operate with, and to increase. So we could add a new numeric
`Id' field and use it as the primary key:
%rec: Item
%key: Id
%mandatory: Description
Id: 0
Description: 2cm metal soldier WWII
Amount: 2111
Id: 1
Description: Flying Helicopter Indoor Maxi
Amount: 8
...
A problem of this approach is that we must be careful to not assign
already used ids when we introduce more articles in the database. Other
than its uniqueness, it is not important which number is associated
with which article.
To ease the management of those Ids database systems use to provide a
facility called "auto-counters". Auto-counters can be implemented in
recfiles using the `%auto' directive in the record descriptor:
%rec: Item
%key: Id
%type: Id int
%mandatory: Description
%auto: Id
Id: 0
Description: 2cm metal soldier WWII
Amount: 2111
Next time a new item is introduced in the database, the conforming
application will note the `%auto', and will create a new `Id' field for
the new record with the bigger unused integer available. In this
example, the new record will have an Id of `1'. The application can
still provide an explicit Id for the new record. In that case the
field is not generated automatically.
The concrete effect of the `%auto' directive depends on the type of
the affected field:
- If it is an `integer' or a `range' then the biggest non-used
number in the record set will be generated.
- If it is a `date' then a field with the current date will be
generated.
- If no explicit type is defined for an auto generated field it is
assumed to be an integer.
- Auto generated fields with other types are not allowed.
Auto generated dates can be used to implement automatic timestamps.
Consider for example a "Transfer" record set registering bank
transfers. We want to save a timestamp every time a transfer is done,
so we include an `%auto' for the date:
%rec: Transfer
%key: Id
%type: Id int
%type: Date date
%auto: Id Date
Note that the auto fields are generated at the beginning of the new
records, in the same order they are found in the `%auto' directives.
12 %sort
********
This special field allows to set a sorting criteria for the records
contained in a record set. Its usage is:
%sort: FIELD_NAME
Meaning that the desired order for the records will be determined by
the contents of the fields named `field_name'. The sorting is always
done in ascending order, and there may be records not featuring fields
named `field_name', i.e. it is not mandatory for the sorting field to
be mandatory :D.
It is an error to have more than one `%sort' field in the same
record descriptor, as only one field can be used as sorting criteria.
Consider for example that we want to keep the records in our stockage
system ordered by entry date. We could achieve that by using the
following record descriptor in the database:
%rec: Item
%type: Date date
%sort: Date
Id: 1
Title: Staplers
Date: 10 February 2011
Id: 2
Title: Ruler Pack 20
Date: 2 March 2009
...
As you can see in the example above, the fact we use `%sort' in a
database does not mean that the database will be always physically
ordered. Unsorted record sets are not considered a data integrity
problem, and thus the diagnosis tools must not declare a recfile as
invalid because of this. Some tool may provide a way to physically
order the fields in the file. That is certainly the case of the GNU
recutils, where `recfix' can be used for that purpose. *Note recfix::.
On the other hand any program listing, presenting or processing data
extracted from the recfile must honour the `%sort' entry. For example,
when using the following `recsel' program in the database above we
would get the output sorted by date:
$ recsel stockage.rec
Id: 2
Title: Ruler Pack 20
Date: 2 March 2009
Id: 1
Title: Staplers
Date: 10 February 2011
The sorting of the selected field depends on its type:
- Numeric fields (integers, ranges, reals) are numerically ordered.
- Boolean fields are ordered considering that "false" values come
first.
- Dates are ordered as expected.
- Any other kind of field is ordered using a lexicographic order.
13 %size
********
This special field is used to define constraints in the number of
records stored in a record set. Its usage is:
%size: [RELATIONAL_OPERATOR] NUMBER
If no operator is specified then NUMBER is interpreted as the exact
number of records of this type. The number can be any integer literal,
including hexadecimal and octal constants. For example:
%rec: Day
%size: 7
%type: Name enum
+ Monday Tuesday Wednesday Thursday Friday
+ Saturday Sunday
%doc: There should be 7 days.
The optional RELATIONAL_OPERATOR shall be one of `<', `<=', `>' and
`>='. For example:
%rec: Item
%key: Id
%size: <= 100
%doc: We have at much 100 different articles.
It is valid to specify a size of `0', meaning that no records of
this type shall exist in the file.
This field shall appear only once in a record descriptor.
14 %confidential
****************
This special field allows to declare a set of fields as "confidential",
meaning they contain sensible information such as passwords or secrets.
Its usage is:
%confidential: FIELD1 FIELD2 ... FIELDN
The list of field names are separated by one or more blank characters.
There can be several `%confidential' fields in the same record
descriptor, the effective list of confidential fields being the union
of all the entries.
Declaring a field as confidential indicates that its contents must
not be stored in plain text, but encrypted with a password-based
mechanism. When the information is retrieved from the database the
confidential fields are unencrypted if the correct password is
provided. Likewise, when information is inserted in the database the
confidential fields are encrypted with some given password.
For example, consider a database of users of some service. For each
user we want to store a name, a login name, an email address and a
password. All this information is public with the obvious exception of
the password. Thus we declare the `Password' field as confidential in
the corresponding record descriptor:
%rec: Account
%type: Name line
%type: Login line
%type: Email email
%confidential: Password
The rec format does not impose the usage of a specific encryption
algorithm, but requires that:
- The algorithm must be password-based.
- The value of any encrypted field shall begin with the string
`encrypted-' followed by the encrypted data.
- The encrypted data must be encoded in some ASCII encoding such as
base64.
The above rules assure that it is possible to determine whether a
given field is encrypted. For example, the following is an excerpt
from the account database described above. It contains an entry with
the password encrypted and another with the password unencrypted:
Name: Mr. Foo
Login: foo
Email: foo@foo.com
Password: encrypted-AAABBBCCDDDEEEFFF
Name: Mr. Bar
Login: bar
Email: bar@bar.com
Password: secret
Unencrypted confidential fields are considered a data integrity
error, and utilities like `recfix' will report it. The same utility can
be used to "fix" the database by massively encripting any unencrypted
field.
Nothing prevents the usage of several passwords in the same database.
This allows the establishment of several level of securities or
security profiles. For example, we may want to store different
passwords for different online services:
%rec: Account
%confidential: WebPassword ShellPassword
We could then encrypt WebPassword entries using a password shared among
all the webmasters, and the ShellPassword entries with a more
restricted password available only to the administrator of the machine.
The GNU recutils fully support encypted fields. See the
documentation for `recsel', `recins' and `recfix' for details on how to
operate on files containing confidential fields.
15 Compound Field Names
***********************
*Please note that the features described in this chapter are very
likely to change in the near future. It is thus recommended to not
rely on them in your own databases.*
It is possible to make a reference to a record (or set of records) of
a certain type by using a "compound field name". A compound field is
composed by three components separated by double colon characters (`:'):
TYPE:FIELD[:ROLE]:
The first component is a record type, usually defined somewhere else
(*note Record Descriptors::). The second component is the name of a
field. Finally, an optional third component is the role played by the
referenced field in the referencing record.
The simplest kind of reference is one without an explicit role. It
is used when only one association between records of different types is
desired. Consider for example:
%rec: Maintainer
Name: Jose E. Marchesi
Package:Name: recutils
In the previous example it is pretty clear which role is played by
the referenced package in the `Maintainer' record: it is the package
maintained by the maintainer. But sometimes the role is not that
identifiable. Consider for example the following record:
%rec: Bug
Id: 203
Title: recsel crashes with files bigger than 2gb
Hacker:Name: Smitha Johnson
Seems to be a bug report. But, what is the relationship between
Smitha Johnson and the bug? Is she the reporter? Or perhaps she is the
hacker that is working to fix it? Is she the hacker that closed the
bug? We can clarify the role of Smitha by using the third part of the
compound field: her role.
Id: 203
Title: recsel crashes with files bigger than 2gb
Hacker:Name:Reporter: Smitha Johnson
So now the situation is clear: Smitha is the reporter.
It is possible to make references to different instances of the same
record type by using roles. Supposing that we want to record who is
the assignee of the bug report, we can introduce the new role
`Assignee':
Id: 203
Title: recsel crashes with files bigger than 2gb
Hacker:Name:Reporter: Smitha Johnson
Hacker:Name:Assignee: Juan Valdes
Note that, like in the case of regular fields, there can be several
compound fields with the same name and the same implicit role in a
record, like in:
%rec: Maintainer
Name: Jose E. Marchesi
Package:Name: GNU PDF
Package:Name: GNU Ferret
Package:Name: GNU rec
Same applies to several compound fields with explicit roles:
%rec: Package
Name: GNU foo
Hacker:Name:Maintainer: Elvis 'The King' Presley
Hacker:Name:Maintainer: Michael 'The other King' Jackson
16 Date input formats
*********************
First, a quote:
Our units of temporal measurement, from seconds on up to months,
are so complicated, asymmetrical and disjunctive so as to make
coherent mental reckoning in time all but impossible. Indeed, had
some tyrannical god contrived to enslave our minds to time, to
make it all but impossible for us to escape subjection to sodden
routines and unpleasant surprises, he could hardly have done
better than handing down our present system. It is like a set of
trapezoidal building blocks, with no vertical or horizontal
surfaces, like a language in which the simplest thought demands
ornate constructions, useless particles and lengthy
circumlocutions. Unlike the more successful patterns of language
and science, which enable us to face experience boldly or at least
level-headedly, our system of temporal calculation silently and
persistently encourages our terror of time.
... It is as though architects had to measure length in feet,
width in meters and height in ells; as though basic instruction
manuals demanded a knowledge of five different languages. It is
no wonder then that we often look into our own immediate past or
future, last Tuesday or a week from Sunday, with feelings of
helpless confusion. ...
-- Robert Grudin, `Time and the Art of Living'.
This section describes the textual date representations that GNU
programs accept. These are the strings you, as a user, can supply as
arguments to the various programs. The C interface (via the
`parse_datetime' function) is not described here.
16.1 General date syntax
========================
A "date" is a string, possibly empty, containing many items separated
by whitespace. The whitespace may be omitted when no ambiguity arises.
The empty string means the beginning of today (i.e., midnight). Order
of the items is immaterial. A date string may contain many flavors of
items:
* calendar date items
* time of day items
* time zone items
* combined date and time of day items
* day of the week items
* relative items
* pure numbers.
We describe each of these item types in turn, below.
A few ordinal numbers may be written out in words in some contexts.
This is most useful for specifying day of the week items or relative
items (see below). Among the most commonly used ordinal numbers, the
word `last' stands for -1, `this' stands for 0, and `first' and `next'
both stand for 1. Because the word `second' stands for the unit of
time there is no way to write the ordinal number 2, but for convenience
`third' stands for 3, `fourth' for 4, `fifth' for 5, `sixth' for 6,
`seventh' for 7, `eighth' for 8, `ninth' for 9, `tenth' for 10,
`eleventh' for 11 and `twelfth' for 12.
When a month is written this way, it is still considered to be
written numerically, instead of being "spelled in full"; this changes
the allowed strings.
In the current implementation, only English is supported for words
and abbreviations like `AM', `DST', `EST', `first', `January',
`Sunday', `tomorrow', and `year'.
The output of the `date' command is not always acceptable as a date
string, not only because of the language problem, but also because
there is no standard meaning for time zone items like `IST'. When using
`date' to generate a date string intended to be parsed later, specify a
date format that is independent of language and that does not use time
zone items other than `UTC' and `Z'. Here are some ways to do this:
$ LC_ALL=C TZ=UTC0 date
Mon Mar 1 00:21:42 UTC 2004
$ TZ=UTC0 date +'%Y-%m-%d %H:%M:%SZ'
2004-03-01 00:21:42Z
$ date --rfc-3339=ns # --rfc-3339 is a GNU extension.
2004-02-29 16:21:42.692722128-08:00
$ date --rfc-2822 # a GNU extension
Sun, 29 Feb 2004 16:21:42 -0800
$ date +'%Y-%m-%d %H:%M:%S %z' # %z is a GNU extension.
2004-02-29 16:21:42 -0800
$ date +'@%s.%N' # %s and %N are GNU extensions.
@1078100502.692722128
Alphabetic case is completely ignored in dates. Comments may be
introduced between round parentheses, as long as included parentheses
are properly nested. Hyphens not followed by a digit are currently
ignored. Leading zeros on numbers are ignored.
Invalid dates like `2005-02-29' or times like `24:00' are rejected.
In the typical case of a host that does not support leap seconds, a
time like `23:59:60' is rejected even if it corresponds to a valid leap
second.
16.2 Calendar date items
========================
A "calendar date item" specifies a day of the year. It is specified
differently, depending on whether the month is specified numerically or
literally. All these strings specify the same calendar date:
1972-09-24 # ISO 8601.
72-9-24 # Assume 19xx for 69 through 99,
# 20xx for 00 through 68.
72-09-24 # Leading zeros are ignored.
9/24/72 # Common U.S. writing.
24 September 1972
24 Sept 72 # September has a special abbreviation.
24 Sep 72 # Three-letter abbreviations always allowed.
Sep 24, 1972
24-sep-72
24sep72
The year can also be omitted. In this case, the last specified year
is used, or the current year if none. For example:
9/24
sep 24
Here are the rules.
For numeric months, the ISO 8601 format `YEAR-MONTH-DAY' is allowed,
where YEAR is any positive number, MONTH is a number between 01 and 12,
and DAY is a number between 01 and 31. A leading zero must be present
if a number is less than ten. If YEAR is 68 or smaller, then 2000 is
added to it; otherwise, if YEAR is less than 100, then 1900 is added to
it. The construct `MONTH/DAY/YEAR', popular in the United States, is
accepted. Also `MONTH/DAY', omitting the year.
Literal months may be spelled out in full: `January', `February',
`March', `April', `May', `June', `July', `August', `September',
`October', `November' or `December'. Literal months may be abbreviated
to their first three letters, possibly followed by an abbreviating dot.
It is also permitted to write `Sept' instead of `September'.
When months are written literally, the calendar date may be given as
any of the following:
DAY MONTH YEAR
DAY MONTH
MONTH DAY YEAR
DAY-MONTH-YEAR
Or, omitting the year:
MONTH DAY
16.3 Time of day items
======================
A "time of day item" in date strings specifies the time on a given day.
Here are some examples, all of which represent the same time:
20:02:00.000000
20:02
8:02pm
20:02-0500 # In EST (U.S. Eastern Standard Time).
More generally, the time of day may be given as
`HOUR:MINUTE:SECOND', where HOUR is a number between 0 and 23, MINUTE
is a number between 0 and 59, and SECOND is a number between 0 and 59
possibly followed by `.' or `,' and a fraction containing one or more
digits. Alternatively, `:SECOND' can be omitted, in which case it is
taken to be zero. On the rare hosts that support leap seconds, SECOND
may be 60.
If the time is followed by `am' or `pm' (or `a.m.' or `p.m.'), HOUR
is restricted to run from 1 to 12, and `:MINUTE' may be omitted (taken
to be zero). `am' indicates the first half of the day, `pm' indicates
the second half of the day. In this notation, 12 is the predecessor of
1: midnight is `12am' while noon is `12pm'. (This is the zero-oriented
interpretation of `12am' and `12pm', as opposed to the old tradition
derived from Latin which uses `12m' for noon and `12pm' for midnight.)
The time may alternatively be followed by a time zone correction,
expressed as `SHHMM', where S is `+' or `-', HH is a number of zone
hours and MM is a number of zone minutes. The zone minutes term, MM,
may be omitted, in which case the one- or two-digit correction is
interpreted as a number of hours. You can also separate HH from MM
with a colon. When a time zone correction is given this way, it forces
interpretation of the time relative to Coordinated Universal Time
(UTC), overriding any previous specification for the time zone or the
local time zone. For example, `+0530' and `+05:30' both stand for the
time zone 5.5 hours ahead of UTC (e.g., India). This is the best way to
specify a time zone correction by fractional parts of an hour. The
maximum zone correction is 24 hours.
Either `am'/`pm' or a time zone correction may be specified, but not
both.
16.4 Time zone items
====================
A "time zone item" specifies an international time zone, indicated by a
small set of letters, e.g., `UTC' or `Z' for Coordinated Universal
Time. Any included periods are ignored. By following a
non-daylight-saving time zone by the string `DST' in a separate word
(that is, separated by some white space), the corresponding daylight
saving time zone may be specified. Alternatively, a
non-daylight-saving time zone can be followed by a time zone
correction, to add the two values. This is normally done only for
`UTC'; for example, `UTC+05:30' is equivalent to `+05:30'.
Time zone items other than `UTC' and `Z' are obsolescent and are not
recommended, because they are ambiguous; for example, `EST' has a
different meaning in Australia than in the United States. Instead,
it's better to use unambiguous numeric time zone corrections like
`-0500', as described in the previous section.
If neither a time zone item nor a time zone correction is supplied,
time stamps are interpreted using the rules of the default time zone
(*note Specifying time zone rules::).
16.5 Combined date and time of day items
========================================
A "combined date and time of day item" specifies the time on a specific
day of the year. This type is needed for formats that cannot be
represented by individual calendar date (*note Calendar date items::)
and time of day (*note Time of day items::) items due to ambiguity.
# ISO 8601 extended date and time of day format
1972-09-24T20:02:00,000000-0500
The ISO 8601 extended date and time of day format is an ISO 8601
date, a `T' character separator, followed by an ISO 8601 time of day.
16.6 Day of week items
======================
The explicit mention of a day of the week will forward the date (only
if necessary) to reach that day of the week in the future.
Days of the week may be spelled out in full: `Sunday', `Monday',
`Tuesday', `Wednesday', `Thursday', `Friday' or `Saturday'. Days may
be abbreviated to their first three letters, optionally followed by a
period. The special abbreviations `Tues' for `Tuesday', `Wednes' for
`Wednesday' and `Thur' or `Thurs' for `Thursday' are also allowed.
A number may precede a day of the week item to move forward
supplementary weeks. It is best used in expression like `third
monday'. In this context, `last DAY' or `next DAY' is also acceptable;
they move one week before or after the day that DAY by itself would
represent.
A comma following a day of the week item is ignored.
16.7 Relative items in date strings
===================================
"Relative items" adjust a date (or the current date if none) forward or
backward. The effects of relative items accumulate. Here are some
examples:
1 year
1 year ago
3 years
2 days
The unit of time displacement may be selected by the string `year'
or `month' for moving by whole years or months. These are fuzzy units,
as years and months are not all of equal duration. More precise units
are `fortnight' which is worth 14 days, `week' worth 7 days, `day'
worth 24 hours, `hour' worth 60 minutes, `minute' or `min' worth 60
seconds, and `second' or `sec' worth one second. An `s' suffix on
these units is accepted and ignored.
The unit of time may be preceded by a multiplier, given as an
optionally signed number. Unsigned numbers are taken as positively
signed. No number at all implies 1 for a multiplier. Following a
relative item by the string `ago' is equivalent to preceding the unit
by a multiplier with value -1.
The string `tomorrow' is worth one day in the future (equivalent to
`day'), the string `yesterday' is worth one day in the past (equivalent
to `day ago').
The strings `now' or `today' are relative items corresponding to
zero-valued time displacement, these strings come from the fact a
zero-valued time displacement represents the current time when not
otherwise changed by previous items. They may be used to stress other
items, like in `12:00 today'. The string `this' also has the meaning
of a zero-valued time displacement, but is preferred in date strings
like `this thursday'.
When a relative item causes the resulting date to cross a boundary
where the clocks were adjusted, typically for daylight saving time, the
resulting date and time are adjusted accordingly.
The fuzz in units can cause problems with relative items. For
example, `2003-07-31 -1 month' might evaluate to 2003-07-01, because
2003-06-31 is an invalid date. To determine the previous month more
reliably, you can ask for the month before the 15th of the current
month. For example:
$ date -R
Thu, 31 Jul 2003 13:02:39 -0700
$ date --date='-1 month' +'Last month was %B?'
Last month was July?
$ date --date="$(date +%Y-%m-15) -1 month" +'Last month was %B!'
Last month was June!
Also, take care when manipulating dates around clock changes such as
daylight saving leaps. In a few cases these have added or subtracted
as much as 24 hours from the clock, so it is often wise to adopt
universal time by setting the `TZ' environment variable to `UTC0'
before embarking on calendrical calculations.
16.8 Pure numbers in date strings
=================================
The precise interpretation of a pure decimal number depends on the
context in the date string.
If the decimal number is of the form YYYYMMDD and no other calendar
date item (*note Calendar date items::) appears before it in the date
string, then YYYY is read as the year, MM as the month number and DD as
the day of the month, for the specified calendar date.
If the decimal number is of the form HHMM and no other time of day
item appears before it in the date string, then HH is read as the hour
of the day and MM as the minute of the hour, for the specified time of
day. MM can also be omitted.
If both a calendar date and a time of day appear to the left of a
number in the date string, but no relative item, then the number
overrides the year.
16.9 Seconds since the Epoch
============================
If you precede a number with `@', it represents an internal time stamp
as a count of seconds. The number can contain an internal decimal
point (either `.' or `,'); any excess precision not supported by the
internal representation is truncated toward minus infinity. Such a
number cannot be combined with any other date item, as it specifies a
complete time stamp.
Internally, computer times are represented as a count of seconds
since an epoch--a well-defined point of time. On GNU and POSIX
systems, the epoch is 1970-01-01 00:00:00 UTC, so `@0' represents this
time, `@1' represents 1970-01-01 00:00:01 UTC, and so forth. GNU and
most other POSIX-compliant systems support such times as an extension
to POSIX, using negative counts, so that `@-1' represents 1969-12-31
23:59:59 UTC.
Traditional Unix systems count seconds with 32-bit two's-complement
integers and can represent times from 1901-12-13 20:45:52 through
2038-01-19 03:14:07 UTC. More modern systems use 64-bit counts of
seconds with nanosecond subcounts, and can represent all the times in
the known lifetime of the universe to a resolution of 1 nanosecond.
On most hosts, these counts ignore the presence of leap seconds.
For example, on most hosts `@915148799' represents 1998-12-31 23:59:59
UTC, `@915148800' represents 1999-01-01 00:00:00 UTC, and there is no
way to represent the intervening leap second 1998-12-31 23:59:60 UTC.
16.10 Specifying time zone rules
================================
Normally, dates are interpreted using the rules of the current time
zone, which in turn are specified by the `TZ' environment variable, or
by a system default if `TZ' is not set. To specify a different set of
default time zone rules that apply just to one date, start the date
with a string of the form `TZ="RULE"'. The two quote characters (`"')
must be present in the date, and any quotes or backslashes within RULE
must be escaped by a backslash.
For example, with the GNU `date' command you can answer the question
"What time is it in New York when a Paris clock shows 6:30am on October
31, 2004?" by using a date beginning with `TZ="Europe/Paris"' as shown
in the following shell transcript:
$ export TZ="America/New_York"
$ date --date='TZ="Europe/Paris" 2004-10-31 06:30'
Sun Oct 31 01:30:00 EDT 2004
In this example, the `--date' operand begins with its own `TZ'
setting, so the rest of that operand is processed according to
`Europe/Paris' rules, treating the string `2004-10-31 06:30' as if it
were in Paris. However, since the output of the `date' command is
processed according to the overall time zone rules, it uses New York
time. (Paris was normally six hours ahead of New York in 2004, but
this example refers to a brief Halloween period when the gap was five
hours.)
A `TZ' value is a rule that typically names a location in the `tz'
database (http://www.twinsun.com/tz/tz-link.htm). A recent catalog of
location names appears in the TWiki Date and Time Gateway
(http://twiki.org/cgi-bin/xtra/tzdate). A few non-GNU hosts require a
colon before a location name in a `TZ' setting, e.g.,
`TZ=":America/New_York"'.
The `tz' database includes a wide variety of locations ranging from
`Arctic/Longyearbyen' to `Antarctica/South_Pole', but if you are at sea
and have your own private time zone, or if you are using a non-GNU host
that does not support the `tz' database, you may need to use a POSIX
rule instead. Simple POSIX rules like `UTC0' specify a time zone
without daylight saving time; other rules can specify simple daylight
saving regimes. *Note Specifying the Time Zone with `TZ': (libc)TZ
Variable.
16.11 Authors of `parse_datetime'
=================================
`parse_datetime' started life as `getdate', as originally implemented
by Steven M. Bellovin () while at the University
of North Carolina at Chapel Hill. The code was later tweaked by a
couple of people on Usenet, then completely overhauled by Rich $alz
() and Jim Berets () in August, 1990.
Various revisions for the GNU system were made by David MacKenzie, Jim
Meyering, Paul Eggert and others, including renaming it to `get_date' to
avoid a conflict with the alternative Posix function `getdate', and a
later rename to `parse_datetime'. The Posix function `getdate' can
parse more locale-specific dates using `strptime', but relies on an
environment variable and external file, and lacks the thread-safety of
`parse_datetime'.
This chapter was originally produced by Franc,ois Pinard
() from the `parse_datetime.y' source code,
and then edited by K. Berry ().
17 Regular Expressions
**********************
The character `.' matches any single character except the null
character.
`+'
indicates that the regular expression should match one or more
occurrences of the previous atom or regexp.
`?'
indicates that the regular expression should match zero or one
occurrence of the previous atom or regexp.
`\+'
matches a `+'
`\?'
matches a `?'.
Bracket expressions are used to match ranges of characters. Bracket
expressions where the range is backward, for example `[z-a]', are
invalid. Within square brackets, `\' is taken literally. Character
classes are supported; for example `[[:digit:]]' will match a single
decimal digit.
GNU extensions are supported:
1. `\w' matches a character within a word
2. `\W' matches a character which is not within a word
3. `\<' matches the beginning of a word
4. `\>' matches the end of a word
5. `\b' matches a word boundary
6. `\B' matches characters which are not a word boundary
7. `\`' matches the beginning of the whole input
8. `\'' matches the end of the whole input
Grouping is performed with parentheses `()'. An unmatched `)'
matches just itself. A backslash followed by a digit acts as a
back-reference and matches the same thing as the previous grouped
expression indicated by that number. For example `\2' matches the
second group expression. The order of group expressions is determined
by the position of their opening parenthesis `('.
The alternation operator is `|'.
The characters `^' and `$' always represent the beginning and end of
a string respectively, except within square brackets. Within brackets,
`^' can be used to invert the membership of the character class being
specified.
`*', `+' and `?' are special at any point in a regular expression
except the following places, where they are not allowed:
1. At the beginning of a regular expression
2. After an open-group, signified by `('
3. After the alternation operator `|'
Intervals are specified by `{' and `}'. Invalid intervals such as
`a{1z' are not accepted.
The longest possible match is returned; this applies to the regular
expression as a whole and (subject to this constraint) to
subexpressions within groups.
18 Common Options
*****************
Certain options are available in all of these programs. Rather than
writing identical descriptions for each of the programs, they are
described here.
`--version'
Print the version number, then exit successfully.
`--help'
Print a help message, then exit successfully.
`--'
Delimit the option list. Later arguments, if any, are treated as
operands even if they begin with `-'. For example, `recsel -- -p'
reads from the file named `r'.
18.1 Selection Expressions
==========================
"Selection expressions" (also known as a SEXs) are simple infix
expressions that can be applied to a record. The result of the SEX is
typically interpreted as a Boolean value.
18.1.1 Operands
---------------
The supported operands are: numbers, strings, field names and
parenthesized expressions.
18.1.1.1 Numeric Literals
.........................
The supported numeric literals are integer numbers and real numbers.
The usual sign character `-' is used to denote negative values.
Integer values can be denoted in base 10, base 16 using the `0x'
prefix, and base 8 using the `0' prefix. Examples are:
10000
0
0xFF
-0xa
012
-07
-1342
.12
-3.14
18.1.1.2 String Literals
........................
String values are delimited by either the `'' character or the `"'
character. Whatever delimiter is used, the delimiter closing the
literal shall equal to the delimiter used to open it.
Note that newlines and tabs can be part of a string literal.
Examples are:
'Hello.'
'The following example is the empty string.'
''
The `'' and `"' characters can be part of a string if they are
escaped with a backslash, like in:
'This string contains an apostrophe: \'.'
"This one a double quote: \"."
18.1.1.3 Field Values
.....................
The value of a field value can be included in a selection expression by
writing its name. The field name is replaced by a string containing
the field value, covering any possibility with records with more than
one field featuring that name. The last colon character (`:') of the
field name is optional. Examples:
Name
Email:
Hacker:Name:OpenedBy
It is possible to use the role part of a field if it is not empty.
So, for example, if we are searching for the issues opened by `John
Smith' in a database of issues we could write:
$ recsel -e "OpenedBy = 'John Smith'"
instead of using the full field name:
$ recsel -e "Hacker:Name:OpenedBy = 'John Smith'"
When the name of a field appears in an expression, the expression is
applied to all the fields in the record featuring that name. So, for
example, the expression:
Email ~ "\\.org"
Will match any record in which there is a field named `Email' whose
value terminates in `.org'. If we are interested in the value of some
specific email, we can specify its relative position into the
containing record by using "subscripts". Consider, for example:
Email[0] ~ "\\.org"
Will match for:
Name: Mr. Foo
Email: foo@foo.org
Email: mr.foo@foo.com
But not for:
Name: Mr. Foo
Email: mr.foo@foo.com
Email: foo@foo.org
The regexp flavor supported in selection expressions are the POSIX
EREs plus several GNU extensions. *Note Regular Expressions::.
18.1.1.4 Parenthesized Expressions
..................................
Parenthesis characters (`(' and `)') can be used to group sub
expressions in the usual way.
18.1.2 Operators
----------------
The supported operators are arithmetic operators (addition,
subtraction, multiplication, division and modulus), logical operators,
string operators and field operators.
18.1.2.1 Arithmetic Operators
.............................
Arithmetic operators for addition (`+'), subtraction (`-'),
multiplication (`*'), integer division (`/') and modulus (`%') are
supported with their usual meanings.
These operators require either numeric operands or string operands
whose value can be interpreted as numbers (integer or real).
18.1.2.2 Boolean Operators
..........................
The boolean operators *and* (`&&'), *or* (`||') and *not* (`!') are
supported with the same semantics as their C counterparts.
The boolean operators expect integer operands, and will try to
convert any string operand to an integer value.
18.1.2.3 Comparison Operators
.............................
The compare operators *less than* (`<'), *greater than* (`>'), *less
than or equal* (`<='), *greater than or equal* (`>='), *equal* (`=')
and *unequal* (`!=') are supported with their usual meaning.
Strings can be compared with the equality operator (`=').
The match operator (`~') can be used to match a string with a given
regular expression. The supported regexp syntax is described in the
GNU C library manual.
18.1.2.4 Date Comparison Operators
..................................
The compare operators *before* (`<<'), *after* (`>>') and *same time*
(`==') can be used with fields and strings containing parseable dates.
*Note Date input formats::.
18.1.2.5 Field Operators
........................
Field counters are replaced by the number of occurrences of a field
with the given name in the record. For example:
#Email
The previous expression is replaced with the number of fields named
`Email' in the record. It can be zero if the record does not have a
field with that name.
18.1.2.6 String Operators
.........................
The string concatenation operator (`&') can be used to concatenate any
number of strings and field values.
'foo' & Name & 'bar'
18.1.2.7 Conditional Operator
.............................
The ternary conditional operator can be used to select alternatives
based on the value of some expression:
expr1 ? expr2 : expr3
If `expr1' evaluates to true (i.e. it is an integer or the string
representation of an integer and its value is not zero) then the
operator yields `expr2'. Otherwise it yields `expr3'.
Note that there should be always at least one blank character between
`expr2' and the colon (`:') if `expr2' is a field name. This is
because field names can optionally end with a colon.
18.1.3 Evaluation of Selection Expressions
------------------------------------------
Given that:
- It is possible to refer to fields by name in selection expressions.
- Records can have several fields featuring the same name.
It is clear that some backtracking mechanism is needed in the
evaluation of the selection expressions. For example, consider the
following expression that is deciding whether a "registration" in a
webpage shall be rejected:
((Email ~ "foomail\.com") || (Age <= 18)) && !#Fixed
The previous expression will be evaluated for every possible
permutation of the fields "Email", "Age" and "Fixed" present in the
record, until one of the combinations succeeds. At that point the
computation is interrupted.
When used to decide whether a record matches some criteria, the goal
of a selection expression is to act as a boolean expression. In that
case the final value of the expression depends on both the type and the
value of the result launched by the top-most subexpression:
- If the result is an integer, the expression is true if its value
is not zero.
- If the result is a real, or a string, the expression evaluates to
false.
Sometimes a selection expression is used to compute a result instead
of a boolean. In that case the returned value is converted to a
string. This is used when replacing the slots in templates (*note
recfmt Templates::).
18.2 Field Expressions
======================
"Field expressions" (also known as FEXs) are a way to select fields of
a record.
A FEX is composed by a sequence of "elements" separated by commas:
ELEM_1,ELEM_2,...,ELEM_N
Each element makes a reference to one or more fields in a record
identified by a given name and an optional subscript:
FIELD_NAME[MIN-MAX]
MIN and MAX are zero-based indexes. It is possible to refer to a field
occupying a given position. For example, consider the following record:
Name: Mr. Foo
Email: foo@foo.com
Email: foo@foo.org
Email: mr.foo@foo.org
We would select all the emails of the record with:
Email
The first email with:
Email[0]
The third email with:
Email[2]
The second and the third email with:
Email[1-2]
And so on. Note that a selection is an ordered set not allowing
duplicated values. Thus, the field expression:
Email[0],Name,Email
is equivalent to
Email[0],Name,Email[1-2]
19 recinf
*********
`recinf' reads the given rec files (or the data in the standard input
if no file is specified) and prints information about it.
19.1 recinf Invocation
======================
`recinf' reads the given rec files (or the data in the standard input
if no file is specified) and prints a resume of the record types
contained in the input.
Synopsis:
recinf [OPTION]... [FILE]...
The default behavior of the tool is to emit a line per record type in
the input containing its name and the number of records of that type:
$ recinf hackers.rec tasks.rec
25 Hacker
102 Task
If the input contains anonymous records, i.e. records that are before
the first record descriptor, the corresponding line resume won't have a
type name:
$ recinf data.rec
10
In addition of the common options described earlier (*note Common
Options::) the program accepts the following options.
`-t TYPE'
`--type=TYPE'
Select records of a given type only.
`-d'
`--descriptor'
Print all the record descriptors present in the file.
`-n'
`--names-only'
Output just the names of the record types found in the input. If
the input is composed by anonymous records only then don't emit any
output.
`--print-sexps'
Print the data in the form of sexps (lisp expressions) instead of
rec format. This option is intended to be used by lisp programs.
20 recsel
*********
`recsel' reads the given rec files (or the data in the standard input
if no file is specified) and prints out records (or part of records)
based in some criteria specified by the user.
20.1 recsel Invocation
======================
`recsel' searches rec files for records satisfying a certain criteria.
Synopsis:
recsel [OPTION]... [-n INDEXES | -e RECORD_EXPR | -q STR | -m NUM] [-c | (-p|-P|-R) FIELD_EXPR] \
[FILE]...
In addition of the common options described earlier (*note Common
Options::) the program accepts the following options.
If no FILE is specified then the command acts like a filter, getting
the data from the standard input and writing the result in the standard
output.
The following "global options" are available.
`-C'
`--collapse'
Do not section the result in records with newlines.
`-d'
`--include-descriptors'
Print record descriptors along with the matched records
`-s SECRET'
`--password=SECRET'
Try to decrypt confidential fields with the given password.
`-S'
`--sort=FIELD'
Sort the output by FIELD. This option has precedence to whatever
sorting criteria is specified in the corresponding record
descriptor with `%sort'.
`-U'
`--uniq'
Remove duplicated fields in the output records. Fields are
duplicated if there are more than one featuring the same field name
and the same value.
The "selection options" are used to select a subset of the records
in the input.
`-n INDEXES'
Match the records occupying the given positions in its record set.
INDEXES must be a comma-separated list of numbers or ranges, the
ranges being two numbers separated with dashes. For example, the
following list denotes the first, the third, the fourth and all
records up to the tenth: `-n 0,2,4-9'.
`-e EXPR'
`--expression=EXPR'
A record selection expression (*note Selection Expressions::).
Only the records matched by the expression will be taken into
account to compute the output.
`-q STR'
`--quick=STR'
Select records having a field whose value contains the substring
STR.
`-m NUM'
`--random=NUM'
Select NUM random records. If NUM is zero then select all the
records.
`-t TYPE'
`--type=TYPE'
Select records of a given type only.
The "output options" are used to determine what information about
the selected records to display to the user, and how to display it.
`-p NAME_LIST'
`--print=NAME_LIST'
List of fields to print for each record. NAME_LIST is a list of
field names separated by commas. For example:
-p Name,Email
means to print the Name and the Email of every matching record.
If this option is not specified then all the fields of the matching
records are printed in the standard output.
`-P NAME_LIST'
`--print-values=NAME_LIST'
Same than `-p', but print the values of the selected fields.
`-R NAME_LIST'
`--print-row=NAME_LIST'
Same than `-P', but print the values separated by single spaces
instead of newlines.
`-c'
`--count'
If this option is specified then recsel will print the number of
matching records instead of the records themselves. This option is
incompatible with `-p', `-P' and `-R'.
Some "special options" are available to ease the communication
between the recutils and other programs, such as lisp interpreters.
Those options are not intended to be used by human operators.
`--print-sexps'
Print the data using sexps instead of rec format.
20.2 recsel Examples
====================
Print the closed bugs:
$ recsel -t Task -e "Status = 'CLOSED'" TODO.rec
Print the name of all the registrants less than twenty:
$ recsel -e 'Age < 20' -P Partner registrants.rec
20.3 recsel Encryption
======================
The contents of confidential fields can be read using the
`-s|--password' command line option to `recsel'. When used, any
selected record containing encrypted fields will try to decrypt them
with the given password. If the operation succeeds then the output
will include the unencrypted data. Otherwise the ASCII-encoded
encrypted data will be emitted.
If `recsel' is invoked interactively and no password is specified
with `-s', the user will be asked for a password in case one is needed.
No echo of the password will appear in the screen. The provided
password will be used to decrypt all confidential fields as if it was
specified with `-s'.
For example, consider the following database storing information
about the user accounts of some online service. Each entry stores a
login, a full name, email and a password. The password is declared as
confidential:
%rec: Account
%key: Login
%confidential: Password
Login: foo
Name: Mr. Foo
Email: foo@foo.com
Password: encrypted-AAABBBCCCDDD
Login: bar
Name: Ms. Bar
Email: bar@bar.org
Password: encrypted-XXXYYYZZZUUU
If we use `recsel' to get a list of records of type `Account' without
specifying a password, or if the wrong password was specified in
interactive mode, then we would get the following output with the
encrypted values:
$ cat accounts.rec | recsel -t Account -p Login,Password
Login: foo
Password: encrypted-AAABBBCCCDDD
Login: bar
Password: encrypted-XXXYYYZZZUUU
If we specify a password and both entries were encrypted using that
password, we would get the unencrypted values:
$ recsel -t Account -s secret -p Login,Password accounts.rec
Login: foo
Password: foosecret
Login: bar
Password: barsecret
Note that nothing prevents to have confidential fields encrypted with
different passwords. As discussed in *note %confidential:: this can be
useful to implement several "levels" of security. For example, we may
have an entry in our database with data about the account of the
administrator of the online service. In that case we could want to
store the password associated with that account using a differentiated
password. In that case the output of the last command would have been:
$ recsel -t Account -s secret -p Login,Password accounts.rec
Login: foo
Password: foosecret
Login: bar
Password: barsecret
Login: admin
Password: encrypted-TTTVVVBBBNNN
We would need to invoke `recsel' with the password used to encrypt the
admin entry in order to read it back unencrypted.
21 recins
*********
`recins' adds new records to a rec file or to rec data read from the
standard input.
21.1 recins Invocation
======================
`recins' adds new records to a rec file or to rec data read from the
standard input. Synopsis:
recins [OPTION]... [t TYPE] [-n INDEXES | -e EXPR | -q STR | -m NUM] \
[(-f STR -v STR]|[-r RECDATA)]... [FILE]
The new record that will be inserted by the command is constructed by
using pairs of `-f' and `-v' options. Each pair defines a field. The
order of the parameters is significant.
If no FILE is specified then the command acts like a filter, getting
the data from the standard input and writing the result in the standard
output.
If the specified FILE does not exist, it is created.
In addition to the common options described earlier (*note Common
Options::) the program accepts the following options.
`-t'
`--type=EXPR'
The type of the new record. If there is a record set in the input
data matching this type then the new record is added there.
Otherwise a new record set is created. If this parameter is not
specified then the new record is anonymous.
`-f'
`--field=NAME'
Declares the name of a field. This option shall be followed by a
`-v'.
`-v'
`--value=VALUE'
The value of the field being defined.
`-r'
`--record=VALUE'
Add the fields of the record in VALUE. This option can be
intermixed with `-f ... -v' pairs.
`-s'
`--password'
Encrypt confidential fields with the given password.
`--no-external'
Don't use external record descriptors.
`--verbose'
Be verbose when reporting integrity problems.
`--no-auto'
Don't generate "auto" fields. *Note %auto::.
Record selection arguments are supported as well. If they are used
then `recins' enters in "replacement mode". Instead of appending the
new record, matched records are replaced by copies of the provided
record. The selection arguments are summarized in the next table.
`-n INDEXES'
Match the records occupying the given positions in its record set.
INDEXES must be a comma-separated list of numbers or ranges, the
ranges being two numbers separated with dashes. For example, the
following list denotes the first, the third, the fourth and all
records up to the tenth: `-n 0,2,4-9'.
`-e EXPR'
`--expression=EXPR'
A record selection expression (*note Selection Expressions::).
Matching records will get replaced.
`-q STR'
`--quick=STR'
Remove records having a field whose value contains the substring
STR.
`-m NUM'
`--random=NUM'
Select NUM random records. If NUM is zero then all records are
selected, i.e. no replace mode is activated.
`-i'
`--case-insensitive'
Make strings case-insensitive in selection expressions.
21.2 recins Examples
====================
Create a new issue in the bugs database:
$ recins -t Task -f Id -v 10 \
-f Title -v "New issue." \
-f Status -v NEW \
TODO.rec
Register a new event in a log file, using recins as a filter:
recins -f Date -v `date` -f Entry -v "$HW_ADDR device connected" \
< $LOGFILE > $LOGFILE.t \
&& cat $LOGFILE.t >> $LOGFILE
21.3 recins Encryption
======================
`recins' allows the insertion of encrypted fields in a database. When
the `-s|--password' command line option is specified in the command
line any field declared as confidential in the record descriptor will
get encrypted using the given passphrase. If the command is executed
interactively and `-s' is not used then the user is asked to provide a
password using the terminal. For example, the invocation:
$ recins -t Account -s mypassword -f Login -v foo -f Password -v secret accounts.rec
Will encrypt the value of the `Password' field with `mypassword' as
long as the field is declared as confidential. See *note
%confidential:: for details on confidential fields.
`recins' will issue a warning if a confidential field is inserted in
the database but no password was provided to encrypt it. This is to
avoid having unencrypted sensible data in the recfiles.
22 recdel
*********
`recdel' removes records from a rec file, or from rec data read from
the standard input.
22.1 recdel Invocation
======================
`recdel' removes records from a rec file, or from rec data read from
the standard input. Synopsis:
recdel [OPTIONS]... [-t TYPE] [-n INDEXES | -e EXPR | -q STR | -m NUM] [FILE]
If no FILE is specified then the command acts like a filter, getting
the data from the standard input and writing the result in the standard
output.
In addition to the common options described earlier (*note Common
Options::) the program accepts the following options.
`-t'
`--type=EXPR'
Remove records of the given type. If this parameter is not
specified then records of any type will be removed.
`-n INDEXES'
Match the records occupying the given positions in its record set.
INDEXES must be a comma-separated list of numbers or ranges, the
ranges being two numbers separated with dashes. For example, the
following list denotes the first, the third, the fourth and all
records up to the tenth: `-n 0,2,4-9'.
`-e EXPR'
`--expression=EXPR'
A record selection expression (*note Selection Expressions::).
Only the records matched by the expression will be removed from
the file.
`-q STR'
`--quick=STR'
Remove records having a field whose value contains the substring
STR.
`-m NUM'
`--random=NUM'
Remove NUM random records. If NUM is zero then remove all the
records.
`-c'
`--comment'
Comment the matching records out instead of removing them.
`-f'
`--force'
Delete even in potentially dangerous situations, such as the
request to delete all the records of some type, for example.
`--no-external'
Don't use external record descriptors.
`--verbose'
Be verbose when reporting integrity problems.
22.2 recdel Examples
====================
Comment out closed issues in the bugs database:
$ recdel -c -t Task -e "Status = 'CLOSED'" TODO.rec
23 recset
*********
`recset' manipulates the fields of records in a rec file.
23.1 recset Invocation
======================
`recset' manipulates the fields of records in a rec file, or rec data
read from the standard input. Synopsis:
recset [OPTION]... [FILE]...
If no FILE is specified then the command acts like a filter, getting
the data from the standard input and writing the result in the standard
output.
In addition to the common options described earlier (*note Common
Options::) the program accepts the following options.
Record selection options:
`-i'
`--case-insensitive'
Make strings case-insensitive in selection expressions.
`-t'
`--type=EXPR'
Operate on the records of the given type. If this parameter is not
specified then records of any type will be removed.
`-n INDEXES'
Operate on the records occupying the given positions in its record
set. INDEXES must be a comma-separated list of numbers or ranges,
the ranges being two numbers separated with dashes. For example,
the following list denotes the first, the third, the fourth and
all records up to the tenth: `-n 0,2,4-9'.
`-e EXPR'
`--expression=EXPR'
A record selection expression (*note Selection Expressions::).
Only the records matched by the expression will be processed.
`-q STR'
`--quick=STR'
Operate on records having a field whose value contains the
substring STR.
`-m NUM'
`--random=NUM'
Operate on NUM random records. If NUM is zero then operate on all
the records.
Fields selection options:
`-f'
`--fields=FEX'
Field selection expression (*note Field Expressions::) to select
the fields to operate.
Actions:
`-s'
`--set=VALUE'
Set the value of the selected fields to VALUE.
`-a'
`--add=VALUE'
Add a new field to the selected record with value VALUE.
`-S'
`--set-add=VALUE'
Set the value of the selected fields to VALUE. If some of the
fields don't exist in a record, append it with the specified value.
`-r'
`--rename=VALUE'
Rename a field. VALUE shall be a valid field name. The field
expression associated with this action shall contain a single field
name and an optional subscript. If an entire record set is
selected then the field is renamed in the record descriptor as
well.
`-d'
`--delete'
Delete the selected fields in the selected records.
`-c'
`--comment'
Comment out the selected fields in the selected records.
`--no-external'
Don't use external record descriptors.
`--verbose'
Be verbose when reporting integrity problems.
`--force'
Perform the requested operation even in potentially dangerous
situations, or when the integrity of the data stored in the fail is
affected.
23.2 recset Examples
====================
Remove "TmpName" fields from any record in "data.rec":
$ recset -f TmpName -d data.rec
Set the secondary email of all friends to `invalid@email.com':
$ recset -f Email[1] -s invalid@email.com friends.rec
Add the email `new@email.com' to John Smith:
$ recset -e "Name = 'John Smith'" -f Email -a new@email.com friends.rec
Rename the secondary email fields from `Email' to `AltEmail'.
Modify the record descriptor as well:
$ recset -f Email[1] -r AltEmail friends.rec
Add a ClosedAt field to the selected record with the current date.
In case it already exists, set its value instead:
$ recset -n 102 -f ClosedAt -S `date` tasks.rec
24 recfix
*********
`recfix' checks and fixes rec files.
24.1 recfix Invocation
======================
`recfix' checks and fixes rec files. Synopsis:
recfix [OPTION]... [OPERATION] [OP_OPTION]... [FILE]
If no FILE is specified then the command acts like a filter, getting
the data from the standard input and writing the result in the standard
output.
In addition to the common options described earlier (*note Common
Options::) the program accepts the following global options.
`--no-external'
Don't use external record descriptors.
The effect of running `recfix' depends on the operation it performs.
The operation mode is selected by using one of the following options.
`--check'
Check the integrity of the database contained in the file, printing
diagnostics messages in case something is not right. This is the
default operation.
`--sort'
Perform a physical sort of all the records contained in the file
(or the standard input) after checking for its integrity. The
sorting criteria is provided by the `%sort' special field, if any.
If there is an integrity failure the sorting is not performed.
Note that this is a destructive operation.
`--encrypt'
Encrypt all the non encrypted fields in the database which are
marked as confidential. This operation requires a password. If
no password is specified with `-s' and the program is run in a
terminal, a prompt is used to get the password from the user.
Note that this is a destructive operation.
`--decrypt'
Decrypt all the encrypted fields in the database which are marked
as confidential. This operation requires a password. If no
password is specified with `-s' and the program is run in a
terminal, a prompt is used to get the password from the user.
Note that this is a descructive operation.
`--auto'
Insert auto-generated fields as appropriate in the records which
are missing them.
Note that this is a destructive operation.
Some operations make use of certain specific options, which are
described in the table below.
`-s SECRET'
`--password=SECRET'
Password used to encrypt or decrypt fields.
24.2 recfix Examples
====================
Check and fix a rec database, invoked both destructively and as a
filter:
$ recfix --check data.rec
$ recfix data.rec
$ cat data.rec | recfix --check data.rec
Physically sort the record sets contained in a file:
$ recfix --sort data.rec
Encrypt any non encrypted confidential fields in a file using a given
password:
$ recfix --encrypt -s "passphrase" secrets.rec
Generate `Id' entries in a stockage database in records missing them.
The record descriptor of the `Item' record set must be defining `Id' as
an auto-generated field:
$ recfix --auto stockage.rec
25 recfmt
*********
`recfmt' formats records using templates.
25.1 recfmt Invocation
======================
`recfmt' formats records using templates. Synopsis:
recfmt [OPTION]... [TEMPLATE]
This program always works as a filter, getting the data from the
standard input and writing the result in the standard output.
In addition to the common options described earlier (*note Common
Options::) the program accepts the following options.
`-f'
`--filename=PATH'
Read the template from the file in PATH instead of the command
line.
25.2 recfmt Templates
=====================
A recfmt template is a text string that may contain "template spots".
Those spots are substituted in the template using the information of a
given record. Any text that is not into a spot is literally copied to
the output.
Spots are written surrounded by double curly braces, like:
{{...}}
Spots contain selection expressions, that are executed every time the
template is applied to a record. The spot is then replaced by the
string representation of the value returned by the expression.
For example, consider the following template:
Task {{Id}}: {{Summary}}
------------------------
{{Description}}
--
Created at {{CreatedAt}}
When applied to the following record:
Id: 123
Summary: Fix recfmt.
CreatedAt: 12 December 2010
Description:
+ The recfmt tool shall be fixed, because right
+ now it is leaking 200 megabytes per processed record.
The result is:
Task 123: Fix recfmt.
------------------------
The recfmt tool shall be fixed, because right
now it is leaking 200 megabytes per processed record.
--
Created at 12 December 2010
Note that you can use any selection expression in the slots,
including conditionals and string concatenation.
25.3 recfmt Examples
====================
Apply a template to all the records stored in the `employees.rec' file:
recsel employees.rec | recfmt 'Dear {{Name}}, you are fired.'
Read the template from a file:
recsel employees.rec | recfmt -f fire-letter.tmpl
26 csv2rec
**********
`csv2rec' reads the given comma-separated-values file (or the data in
the standard input if no file is specified) and prints out the
converted rec data, if possible.
26.1 csv2rec Invocation
=======================
`csv2rec' converts CSV data into rec data. Synopsis:
csv2rec [OPTION]... [CSV_FILE]
In addition of the common options described earlier (*note Common
Options::) the program accepts the following options.
`-t TYPE'
`--type=TYPE'
Type of the converted records. If no type is specified then no
type is used.
`-s'
`--strict'
Be strict parsing the csv file.
`-e'
`--omit-empty'
Omit empty fields.
26.2 csv2rec Examples
=====================
Convert from csv to rec:
$ csv2rec contacts.csv > contacts.rec
Used as a filter, and omitting empty fields:
$ cat contacts.csv | csv2rec -e > contacts.rec
27 rec2csv
**********
`rec2csv' reads the given rec files (or the data in the standard input
if no file is specified) and prints out the converted
comma-separated-values.
27.1 rec2csv Invocation
=======================
`rec2csv' converts rec data into CSV data. Synopsis:
rec2csv [OPTION]... [REC_FILE]...
The rec data can be read from files specified in the command line, or
in the standard input. The program echoes the converted data in the
standard output.
In addition of the common options described earlier (*note Common
Options::) the program accepts the following options.
`-t TYPE'
`--type=TYPE'
Type of the records to convert. If no type is specified then the
default records (with no name) are converted.
`-S'
`--sort=FIELD'
Sort the output by FIELD. This option has precedence to whatever
sorting criteria is specified in the corresponding record
descriptor with `%sort'.
27.2 rec2csv Conversion
=======================
Record sets are not tables, even if tables can be easily emulated using
records having the same fields in the same order. For example:
a: value
b: value
c: value
a: value
b: value
c: value
...
There are several ways records are more flexible than tables:
- Fields can appear in a different order in several records.
- There can be several fields with the same name in a single record.
- Records can differ in the number of fields.
Since comma-separated-values files contain tables, the `rec2csv'
utility implements an algorithm that deals with the previous
difficulties, to generate a table that is what the user expects
(likewise).
The algorithm is the following. The utility first scans the
specified record set, building a list with the names that will become
the table header. For each field, a header is added with the form:
FIELDNAME[_N]
where N is a number in the range `2..inf' and is the "index" of the
field in its containing record plus one. For example, consider the
following record set:
a: a1
b: b11
b: b12
c: c1
a: a2
b: b2
d: d2
The corresponding list of headers being:
a b b_2 c a b d
Then duplicates are removed:
a b b_2 c d
The resulting list of headers is then used to build the table in the
generated csv file. In this case:
"a","b","b_2","c","d"
"a1","b11","b12","c1",
"a2","b2",,,"d2"
Note how missing fields are implemented as empty rows in the
generated csv.
27.3 rec2csv Examples
=====================
Generate a csv file out of a rec file:
$ rec2csv foo.rec > foo.csv
Same operation, but using the program as a filter and specifying a
concrete type:
$ cat inventory.rec | rec2csv -t Item > items.csv
28 mdb2rec
**********
`mdb2rec' reads the given mdb file and prints out the converted rec
data, if possible.
28.1 mdb2rec Invocation
=======================
`mdb2rec' converts mdb files into rec data. Synopsis:
mdb2rec [OPTION]... MDB_FILE [TABLE]
All the tables contained in the mdb file are exported unless a table
is specified in the command line.
In addition of the common options described earlier (*note Common
Options::) the program accepts the following options.
`-s'
`--system-tables'
Include system tables in the output.
`-l'
`--list-tables'
Dump a list of the table names contained in the mdb file, one per
line.
`-e'
`--keep-empty-fields'
Don't prune empty fields in the rec output.
28.2 mdb2rec Examples
=====================
Access files ("mdb files") are collections of several relations, also
known as tables. Tables can be either "user tables" storing user data,
or "system tables" storing information such as forms, queries or the
relationships between the tables.
It is possible to get a listing with the names of all tables stored
in a mdb file by calling `mdb2rec' in the following way:
$ mdb2rec -l sales.mdb
Customers
Products
Orders
So `sales.mdb' stores user information in the tables Customers,
Products and Orders. If we want to include system tables in the
listing we can use the `-s' command line option:
$ mdb2rec -s -l sales.mdb
MSysObjects
MSysACEs
MSysQueries
MSysRelationships
Customers
Products
Orders
The tables with names starting with `MSys' are system tables. The
data stored in those tables is either not relevant to the recutils user
(used by the Access program to create forms and the like) or is used in
an indirect way by `mdb2rec' (such as the information from
MSysRelationships).
Let's read some data from the `mdb' file. We can get the relation
of Products in rec format:
$ mdb2rec sales.mdb Products
%rec: Products
%type: ProductID int
%type: ProductName size 80
%type: Discontinued bool
ProductID: 1
ProductName: GNU generation T-shirt
Discontinued: 0
...
A "record descriptor" is created for the record set containing the
generated records, called Products. Note that `mdb2rec' is able to
generate type information for the fields. The list of customers is
similar:
$ mdb2rec sales.mdb Customers
%rec: Customers
%type: CustomerID size 4
%type: CompanyName size 80
%type: ContactName size 60
CustomerID: GSOFT
CompanyName: GNU Soft
ContactName: Jose E. Marchesi
...
The list of orders is a bit more interesting, since it shows how
`mdb2rec' manages the relationships between tables in the `mdb' file.
$ mdb2rec sales.mdb Orders
%rec: Orders
%type: OrderID int
%type: CustomerID size 10
%type: ProductID int
%type: OrderDate date
OrderID: 10248
Customers:CustomerID: FBFOU
Products:ProductID: 1
OrderDate: 2010-08-01T12:30:01
...
Both CustomerID and ProductID are compound fields reflecting
references to the record sets Customers and Products.
Note that `mdb2rec' always uses the default role when the name of
the column in the referring table is the same than the name of the
column in the referred table. This is to avoid redundant compound
field names like Customers:CustomerID:CustomerID:.
If no table is specified in the invocation to `mdb2rec' all the
tables in the file are processed, with the exception of the system
tables, for which `-s' shall be used:
$ mdb2rec sales.mdb
%rec: Products
...
%rec: Customers
...
%rec: Orders
...
Appendix A GNU Free Documentation License
*****************************************
Version 1.3, 3 November 2008
Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
`http://fsf.org/'
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
0. PREAMBLE
The purpose of this License is to make a manual, textbook, or other
functional and useful document "free" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
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being considered responsible for modifications made by others.
This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.
It complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for
free software, because free software needs free documentation: a
free program should come with manuals providing the same freedoms
that the software does. But this License is not limited to
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of subject matter or whether it is published as a printed book.
We recommend this License principally for works whose purpose is
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must delete all sections Entitled "Endorsements."
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to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the
site under CC-BY-SA on the same site at any time before August 1,
2009, provided the MMC is eligible for relicensing.
ADDENDUM: How to use this License for your documents
====================================================
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:
Copyright (C) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:
with the Invariant Sections being LIST THEIR TITLES, with
the Front-Cover Texts being LIST, and with the Back-Cover Texts
being LIST.
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License, to
permit their use in free software.