This manual is for GNU Alive (version 2.0.2, 8 September 2013).
Copyright © 2012, 2013 Thien-Thi Nguyen
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, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the appendix entitled “GNU Free Documentation License”.
|• Introduction:||General purpose and information.|
|• Invoking alive:||How to use GNU Alive.|
|• Configuration:||Changes to make while ‘alive’ sleeps.|
|• GNU Software:||Alive is a part of GNU.|
|• GNU FDL:||Copying and sharing this documentation.|
Sometimes it’s not enough to simply “get on the net”; what’s important is to stay on the net. If the network is depressed, it might start ignoring you. You can use GNU Alive to cheer it up. But, first things first. Do you know what this command:
ping -i 149 ipaddr
does? If you answered “yes” and don’t mind typing that command into a shell, then you do not need GNU Alive, as its functionality is roughly equivalent to that command. In this case, go ahead and save yourself some time and disk space and remove this package from your computer!
If you answered “no” instead, perhaps that’s because you know what
ping ipaddr does, but are not so sure about
Well, it turns out that
-i n means repeat the ping every
n seconds, instead of every second, the default. So now you know,
and can blithely proceed to remove GNU Alive from your computer. Go
ahead, what are you waiting for?
Still here? Fine. You must be curious, then, about the “roughly equivalent” functionality mentioned above. Surely there must be something to recommend GNU Alive. Was such profligate duplication always so?
|• Features:||Some (very slight, indeed) things.|
|• History:||How GNU Alive came to be, and what it might become.|
As previously established (see Introduction), GNU Alive is a package that provides a command-line program to periodically make network contact with (aka “ping”) a specified host. This section describes some differences between ‘ping’ and ‘alive’ (the program).
Like all proper GNU programs, ‘alive’ supports these options, displaying the requested information to stdout and exiting successfully. See Invoking alive.
Note that Inetutils (see GNU Software) ping also supports these options, as it is also a proper GNU program. Other ping programs may or may not.
To keep things simple and consistent, ‘alive’ takes no arguments, and instead reads configuration information from files in the config directory, by default $HOME/.alive.d/.
If that dir does not exist and your system has ‘xdgdirs’1, then the
the config directory is taken to be what ‘xdgdirs alive’
config-home (you can influence this by
setting env var
In any case, if the config dir or those files don’t exist, ‘alive’ uses reasonable defaults.
Each configuration file is rescanned at the top of every loop iteration if its modification time differs from the last check. This means it’s enough to edit a file (and wait); no need to restart the program. See Configuration.
If you specify more than one host, ‘alive’ contacts them in a round-robin fashion. This reduces the annoyance level of some network administrators—always a good idea.
On the other hand, if you don’t specify any hosts, ‘alive’ contacts
The default period, i.e., time between successive contacts, is a random number of seconds in the range 149 to 420, inclusive.
All GNU programs are distributed as source code, of course, but GNU Alive goes further; the source code is also available when you run the program.
This is because ‘alive’ is implemented as a script, a sequence of textual instructions for an “interpreter” program to read and evaluate, rather than a binary file.
Most users don’t care about runtime access to source code, but perhaps you are not like most users.
GNU Alive uses Guile Scheme (see GNU Software) as the implementation language.
Each configuration file is a series of sexps, or
structured expressions, amenable to the Scheme
(Actually, the syntax is designed to be a subset of what Scheme
read can handle, to be friendly also to Emacs Lisp
Most programmers don’t care about sexps, but perhaps you are not like most programmers.
This section describes the evolution of GNU Alive purpose and design. There are two major development phases, both completely independent of the other.
|• Phase 1:||Through 2005.|
|• Phase 2:||2012 and later.|
[TODO: Describe evolution, as advertized—the following is only a description of the state immediately prior to beginning of phase 2 (see Phase 2).]
Originally, GNU Alive was called ‘qadsl’, and had two purposes: to auto-login to certain Swedish dial-up ISPs2; and to maintain the connection via periodic network traffic. Its authors and maintainers were: Jakob "Kuba" Stasilowicz, Peter Strömberg, Kenth Garlöv, Joachim Nilsson, and Jakob Eriksson.
It was implemented in C and ported to GNU/Hurd, several GNU/Linux variants, NetBSD, and FreeBSD. It used a text-based configuration file format for server name and port, user name, login, password, keepalive daemon type and policy, and so forth. Configuration could be done at system (in /etc) level, user (under ~) level, and with corresponding command-line options.
There were two keepalive types, i.e., methods for generating network traffic: HTTP and “ping” (in spirit, not really ICMP). There was debug, pidfile, syslog support. Once running, the daemon could be queried and commanded by another invocation.
The distribution included an example configuration file, installed in
$(sysconfdir); an info-format manual, for
two manpages: alive.8 and alive.conf.5, installed under
(in the appropriate subdirectory of)
The last release of phase 1 GNU Alive was 1.4.0 (2005-02-22), released under GNU GPL v2+ (like all previous releases). There was a small change afterwards that was never released:
Author: Joachim Nilsson <firstname.lastname@example.org> Date: 2005-11-19 12:23:22 +0000 Attempt to lower the impact of non-responding login servers. Don't sleep too long before retrying, it's OK to fail. src/http.c | 8 ++++---- 1 files changed, 4 insertions(+), 4 deletions(-)
The source code comprised a handful of C files for low-level internals
(cross-platform support, e.g.,
strcasecmp); a pair of Yacc/Lex
input files with glue C code, to implement the configuration file parser
module; and 19 .h and .c files, to implement the program
Curiously, the usual mass of Autotools flotsam (i.e., configure script et al, see GNU Software) was checked into the repository. Release 1.4.0 was prepared using GNU Autoconf 2.59 and GNU Automake 1.8.5.
After several years without activity or release (see Phase 1), in 2012 Thien-Thi Nguyen volunteered to adopt GNU Alive with the intent to drop the auto-login functionality, leaving only the periodic ping, and furthermore, to do a rewrite from scratch. (This is why his name appears on the copyright notices, solely.)
Phase 2 GNU Alive is released under GNU GPL v3+, with a new feature set (see Features).
Running ‘alive’ is easy. Simply type ‘alive’ at the shell prompt followed by RET. You can use the shell’s i/o redirection facilities to filter/suppress the output, and its job control facilities to have ‘alive’ execute in the background. For example, with GNU Bash (see GNU Software):
$ alive >/dev/null &
Two other modes of operation are available:
$ alive --version $ alive --help
That’s it! Quite boring, no? The real fun lies in playing with the configuration, either before starting ‘alive’, or while it runs. See Configuration.
Additionally, ‘alive’ responds to certain signals in a more or less well-defined manner. To send it a signal, first note its pid (process id), displayed on the first line output:
$ alive alive: 2012-08-11 16:24:26 restart (pid 9731) [...]
The pid in this example is
9731. Next, use the command-line
$ kill -INT 9731
or Emacs command
M-x signal-process RET 9731 RET 2 RET
specifying this pid and the signal to send. All unhandled signals (not described in the following table) will cause ‘alive’ to die unceremoniously. To see a list, try ‘kill -l’. Handled signals, on the other hand, elicit an acknowledgement on stdout, e.g., ‘received signal 2 (SIGINT)’.
Interrupt the current
sleep(2). This is useful if you change the
configuration and don’t want to wait for the next iteration.
Restart. This is useful if you forget the pid.
Shut down, i.e., display ‘exiting’ and exit successfully.
You can modify ‘alive’ behavior (even while it runs), by writing simple sexps into text files under the config directory (see Features). Information for a configuration item foo is written in file foo.
|• Generally Sexp-ing:||A few minutes here, first.|
|• hosts:||Who to ping.|
|• period:||How long to wait between pings.|
The file format for the configuration items (see Configuration) is composed of comments, structured expressions, and whitespace.
A comment begins with ‘;’ (semicolon) and goes to the end of the line. If you use Emacs, you can add the comment:
;; -*- scheme -*-
on the first line to make comments appear differently, presuming syntax highlighting support is enabled.
A structured expression, for the purposes of GNU Alive, is one of:
A decimal3 number. For instance,
A contiguous sequence of non-whitespace characters that do not include
‘()’ (parentheses), ‘,’ (comma), ‘'’ (apopostrophe, also
known as single-quote), or ‘"’ (double-quote). For instance,
Everything else, that is, all the stuff between comments and structured expressions, is whitespace.
hosts configuration item specifies who to ping.
Each symbol is either a host name or IP address.
;;; hosts (-*- scheme -*-) ;; gateway 10.0.0.1 ;; various hosts, increasingly further out foo.local-lan bar.site-lan baz.example.com ;;; hosts ends here
period configuration item specifies how long to wait between
pings. The units are (integer) seconds. If there is one integer,
‘alive’ uses it as a fixed period. If there are two, the first
must be less than or equal than the second, and ‘alive’ chooses a
random number between (inclusively) the two.
;;; period (-*- scheme -*-) ;; quickly ; 3 ;; languidly ; 391 ;; randomly, but not too quickly 149 420 ;;; period ends here
This appendix describes some other GNU software used in the maintenance, design and implementation of GNU Alive. For more information about the GNU project, please visit http://www.gnu.org/.
Inetutils provides several command-line utilities for working with a network capable of speaking IP (Internet Protocol). Most relevant to GNU Alive is ‘ping’, which ‘alive’ invokes directly, to compose, send, receive and interpret the actual network (on the wire) packets; and “emulates” indirectly (i.e., sleeping and looping, as for ‘ping -i period’).
Guile provides the Scheme interpreter that actually executes the ‘alive’ script, a crucial role certainly. The design choice to use sexps for configuration items is also informed by Guile. Less known perhaps is that Guile plays a part also in the GNU Alive maintenance; e.g., several Scheme programs and modules are used to prepare its home page.
These are indispensable for maintenance. Autoconf is reponsible for the configure script, and Automake is responsible for generating the various Makefile.in files that uphold the rest of the standard GNU build/installation system.
GNU Alive writes to standard output, and thus is amenable to the parent shell’s i/o redirection facilities. We use Bash to document an example of this (see Invoking alive).
Although Alive does not use Emacs directly, the configuration items can be easily manipulated by Emacs (see Configuration), and Emacs has good support for managing child processes, like Bash.
Why not consider writing a user interface to Alive for Emacs?
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|Jump to:||A B C E F G H I N P Q S|
|software, GNU:||GNU Software|
|structured expression:||Generally Sexp-ing|
|Jump to:||A B C E F G H I N P Q S|
home page: http://www.gnuvola.org/software/xdgdirs/
Some contemporary projects in the same functionality space: TeliaTalker, CiC Login, ARAW, qADSL 1.2.x (from a previous maintainer), TeliaADSLCon, Telia ADSL Connection Keeper, “Clever use of netcat”, LF Connection Keeper. Most of these are defunct or obsolete nowadays.
(usually). GNU Alive will also accept
#o52 (octal) and
(hexadecimal) without complaint.