GNU Coreutils

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GNU Coreutils

This manual documents version 8.32 of the GNU core utilities, including the standard programs for text and file manipulation.

Copyright © 1994-2020 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, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”.

• Introduction  Caveats, overview, and authors
• Common options  Common options
• Output of entire files  cat tac nl od base32 base64 basenc
• Formatting file contents  fmt pr fold
• Output of parts of files  head tail split csplit
• Summarizing files  wc sum cksum b2sum md5sum sha1sum sha2
• Operating on sorted files  sort shuf uniq comm ptx tsort
• Operating on fields  cut paste join
• Operating on characters  tr expand unexpand
• Directory listing  ls dir vdir dircolors
• Basic operations  cp dd install mv rm shred
• Special file types  mkdir rmdir unlink mkfifo mknod ln link readlink
• Changing file attributes  chgrp chmod chown touch
• Disk usage  df du stat sync truncate
• Printing text  echo printf yes
• Conditions  false true test expr
• Redirection  tee
• File name manipulation  dirname basename pathchk mktemp realpath
• Working context  pwd stty printenv tty
• User information  id logname whoami groups users who
• System context  date arch nproc uname hostname hostid uptime
• SELinux context  chcon runcon
• Modified command invocation  chroot env nice nohup stdbuf timeout
• Process control  kill
• Delaying  sleep
• Numeric operations  factor numfmt seq
• File permissions  Access modes
• File timestamps  File timestamp issues
• Date input formats  Specifying date strings
• Version sort ordering  Details on version-sort algorithm
• Opening the software toolbox  The software tools philosophy
• GNU Free Documentation License  Copying and sharing this manual
• Concept index  General index 


 — The Detailed Node Listing —

Common Options
• Exit status  Indicating program success or failure
• Backup options  Backup options
• Block size  Block size
• Floating point  Floating point number representation
• Signal specifications  Specifying signals
• Disambiguating names and IDs  chgrp, chown, chroot, id: user and group syntax
• Random sources  Sources of random data
• Target directory  Target directory
• Trailing slashes  Trailing slashes
• Traversing symlinks  Traversing symlinks to directories
• Treating / specially  Treating / specially
• Standards conformance  Standards conformance
• Multi-call invocation  Multi-call program invocation 

Output of entire files
• cat invocation  Concatenate and write files
• tac invocation  Concatenate and write files in reverse
• nl invocation  Number lines and write files
• od invocation  Write files in octal or other formats
• base32 invocation  Transform data into printable data
• base64 invocation  Transform data into printable data
• basenc invocation  Transform data into printable data 

Formatting file contents
• fmt invocation  Reformat paragraph text
• pr invocation  Paginate or columnate files for printing
• fold invocation  Wrap input lines to fit in specified width 

Output of parts of files
• head invocation  Output the first part of files
• tail invocation  Output the last part of files
• split invocation  Split a file into fixed-size pieces
• csplit invocation  Split a file into context-determined pieces 

Summarizing files
• wc invocation  Print newline, word, and byte counts
• sum invocation  Print checksum and block counts
• cksum invocation  Print CRC checksum and byte counts
• b2sum invocation  Print or check BLAKE2 digests
• md5sum invocation  Print or check MD5 digests
• sha1sum invocation  Print or check SHA-1 digests
• sha2 utilities  Print or check SHA-2 digests 

Operating on sorted files
• sort invocation  Sort text files
• shuf invocation  Shuffle text files
• uniq invocation  Uniquify files
• comm invocation  Compare two sorted files line by line
• ptx invocation  Produce a permuted index of file contents
• tsort invocation  Topological sort 

ptx: Produce permuted indexes
• General options in ptx  Options which affect general program behavior
• Charset selection in ptx  Underlying character set considerations
• Input processing in ptx  Input fields, contexts, and keyword selection
• Output formatting in ptx  Types of output format, and sizing the fields
• Compatibility in ptx  The GNU extensions to ptx 

Operating on fields
• cut invocation  Print selected parts of lines
• paste invocation  Merge lines of files
• join invocation  Join lines on a common field 

Operating on characters
• tr invocation  Translate, squeeze, and/or delete characters
• expand invocation  Convert tabs to spaces
• unexpand invocation  Convert spaces to tabs 

tr: Translate, squeeze, and/or delete characters
• Character sets  Specifying sets of characters
• Translating  Changing one set of characters to another
• Squeezing and deleting  Removing characters 

Directory listing
• ls invocation  List directory contents
• dir invocation  Briefly list directory contents
• vdir invocation  Verbosely list directory contents
• dircolors invocation  Color setup for ls 

ls:  List directory contents
• Which files are listed  Which files are listed
• What information is listed  What information is listed
• Sorting the output  Sorting the output
• General output formatting  General output formatting
• Formatting the file names  Formatting the file names 

Basic operations
• cp invocation  Copy files and directories
• dd invocation  Convert and copy a file
• install invocation  Copy files and set attributes
• mv invocation  Move (rename) files
• rm invocation  Remove files or directories
• shred invocation  Remove files more securely 

Special file types
• link invocation  Make a hard link via the link syscall
• ln invocation  Make links between files
• mkdir invocation  Make directories
• mkfifo invocation  Make FIFOs (named pipes)
• mknod invocation  Make block or character special files
• readlink invocation  Print value of a symlink or canonical file name
• rmdir invocation  Remove empty directories
• unlink invocation  Remove files via unlink syscall 

Changing file attributes
• chown invocation  Change file owner and group
• chgrp invocation  Change group ownership
• chmod invocation  Change access permissions
• touch invocation  Change file timestamps 

Disk usage
• df invocation  Report file system disk space usage
• du invocation  Estimate file space usage
• stat invocation  Report file or file system status
• sync invocation  Synchronize cached writes to persistent storage
• truncate invocation  Shrink or extend the size of a file 

Printing text
• echo invocation  Print a line of text
• printf invocation  Format and print data
• yes invocation  Print a string until interrupted 

Conditions
• false invocation  Do nothing, unsuccessfully
• true invocation  Do nothing, successfully
• test invocation  Check file types and compare values
• expr invocation  Evaluate expressions 

test: Check file types and compare values
• File type tests  File type tests
• Access permission tests  Access permission tests
• File characteristic tests  File characteristic tests
• String tests  String tests
• Numeric tests  Numeric tests 

expr: Evaluate expression
• String expressions  + : match substr index length
• Numeric expressions  + - * / %
• Relations for expr  | & < <= = == != >= >
• Examples of expr  Examples of using expr 

Redirection
• tee invocation  Redirect output to multiple files or processes 

File name manipulation
• basename invocation  Strip directory and suffix from a file name
• dirname invocation  Strip last file name component
• pathchk invocation  Check file name validity and portability
• mktemp invocation  Create temporary file or directory
• realpath invocation  Print resolved file names 

Working context
• pwd invocation  Print working directory
• stty invocation  Print or change terminal characteristics
• printenv invocation  Print all or some environment variables
• tty invocation  Print file name of terminal on standard input 

stty: Print or change terminal characteristics
• Control  Control settings
• Input  Input settings
• Output  Output settings
• Local  Local settings
• Combination  Combination settings
• Characters  Special characters
• Special  Special settings 

User information
• id invocation  Print user identity
• logname invocation  Print current login name
• whoami invocation  Print effective user ID
• groups invocation  Print group names a user is in
• users invocation  Print login names of users currently logged in
• who invocation  Print who is currently logged in 

System context
• arch invocation  Print machine hardware name
• date invocation  Print or set system date and time
• nproc invocation  Print the number of processors
• uname invocation  Print system information
• hostname invocation  Print or set system name
• hostid invocation  Print numeric host identifier
• uptime invocation  Print system uptime and load 

date: Print or set system date and time
• Time conversion specifiers  %[HIklMNpPrRsSTXzZ]
• Date conversion specifiers  %[aAbBcCdDeFgGhjmuUVwWxyY]
• Literal conversion specifiers  %[%nt]
• Padding and other flags  Pad with zeros, spaces, etc.
• Setting the time  Changing the system clock
• Options for date  Instead of the current time
• Date input formats  Specifying date strings
• Examples of date  Examples 

SELinux context
• chcon invocation  Change SELinux context of file
• runcon invocation  Run a command in specified SELinux context 

Modified command invocation
• chroot invocation  Run a command with a different root directory
• env invocation  Run a command in a modified environment
• nice invocation  Run a command with modified niceness
• nohup invocation  Run a command immune to hangups
• stdbuf invocation  Run a command with modified I/O buffering
• timeout invocation  Run a command with a time limit 

Process control
• kill invocation  Sending a signal to processes. 

Delaying
• sleep invocation  Delay for a specified time 

Numeric operations
• factor invocation  Print prime factors
• numfmt invocation  Reformat numbers
• seq invocation  Print numeric sequences 


File timestamps
• File timestamps  File timestamp issues 

File permissions
• Mode Structure  Structure of file mode bits
• Symbolic Modes  Mnemonic representation of file mode bits
• Numeric Modes  File mode bits as octal numbers
• Directory Setuid and Setgid  Set-user-ID and set-group-ID on directories 

Date input formats
• General date syntax  Common rules
• Calendar date items  19 Dec 1994
• Time of day items  9:20pm
• Time zone items  EST, PDT, UTC, …
• Combined date and time of day items  1972-09-24T20:02:00,000000-0500
• Day of week items  Monday and others
• Relative items in date strings  next tuesday, 2 years ago
• Pure numbers in date strings  19931219, 1440
• Seconds since the Epoch  @1078100502
• Specifying time zone rules  TZ="America/New_York", TZ="UTC0"
• Authors of parse_datetime  Bellovin, Eggert, Salz, Berets, et al. 

Version sorting order
• Version sort overview  
• Implementation Details  
• Differences from the official Debian Algorithm  
• Advanced Topics   

Opening the software toolbox
• Toolbox introduction  Toolbox introduction
• I/O redirection  I/O redirection
• The who command  The who command
• The cut command  The cut command
• The sort command  The sort command
• The uniq command  The uniq command
• Putting the tools together  Putting the tools together 

Copying This Manual
• GNU Free Documentation License  Copying and sharing this manual

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