Bash Reference Manual - The Diigo Meta page

• 07 Aug 18
  

  Jesse Emond

  bash quote dollar $ ansi C ctf

• 20 Apr 18
  

  shell command substitutions sysadmin bourne

• 16 Aug 17
  

  ljmolina

  "instan"

  bash linux programming shell

• 11 Oct 16
  

  inbaroth

  command line

• 26 May 16
  

  dingodingo

  scripting shell linux unix terminal bash commandline

• 19 May 16
  

  Harish Butani
  • IEEE POSIX Shell and Tools portion of the IEEE POSIX specification
  • Moreover, the shell allows control over the contents of commands’ environments.
  • The ‘$’ character introduces parameter expansion, command substitution, or arithmetic expansion

  1 more annotation...

• 08 Jun 15
  

  ihaku4
  • Process substitution
  • <(list)
  • input for list
  • the output of list
  • process substitution
  • command substitution
  • arithmetic expansion
  • parameter and variable expansion

  6 more annotations...

• 17 May 15
  

  Bash Reference Manual
  

• 12 Mar 15
  

  andrew smith

  bash gnu

• 10 Mar 15
  

  Monica Rivero

  "Shell Operations"

  commands-iOS

  • A shell script is a text file containing shell commands
  • A shell script may be made executable by using the chmod command
• 06 Feb 15
  

  sanguine otaku
• 11 Nov 14
  

  sunzooman

  manual bash shell linux script

• 15 Sep 14
  

  Simeon Panayotov

  bash

• 11 Aug 14
  

  Jules Verne2

  bash linux manual programming

• 28 Jul 14
  

  johnfryar

  bash shell scripting reference manual

• 09 Jun 14
  

  mmeuris

  From Internet Explorer

• 31 Mar 14
  

  philipjrosen

  bash cli

• 12 Feb 14
  

  Marco Viganò

  bash linux reference

• 28 Jan 14
  

  Philip Johnson

  bash reference shell unix manual programming scripting docs howto terminal command commandline linux

• 22 Oct 13
  

  thoughtcook
  • ?

     

    Matches any single character. 
• 03 Oct 13
  

  Alessandro Mascherpa

  bash reference shell unix linux manual scripting programming command-line

• 13 Sep 13
  

  Mitchell Stewart

  bash

• 14 Jun 13
  

  salvianoleao

  Informatica Shell SED GAWK and Regular Expressions

• 01 Jun 13
  

  friends friends

  firefox-extension-development bash

  • Bash Reference Manual
• 04 Apr 13
  

  Álvaro MG

  linux bash reference

• 21 Mar 13
  

  Justin DesRosiers

  Bash reference manual

  bash reference shell unix manual scripting programming guide linux

• 08 Mar 13
  

  Kemal Dogan

  bash linux reference manual scripting shell

• 03 Mar 13
  

  Marc-Alexandre Gagnon

  bash linux reference shell unix manual programming scripting

• 23 Jan 13
  

  Matthew York

  bash scripting programming shell

  • If ‘|&’ is used, the standard error of command1 is connected to command2’s standard input through the pipe; it is shorthand for 2>&1
  • ‘$’ character introduces parameter expansion, command substitution, or arithmetic expansion.
• 19 Jan 13
  

  Ching Yi Chan

  bash linux

• 02 Dec 12
  

  Juan Fernando Jaramillo

  "exec "

  bash shell

• 13 Nov 12
  

  Xavier Parcel

  SHELL BASH LINUX UNIX UBUNTU SCRIPT

• 03 Nov 12
  

  fdemmer

  reference bash shell scripting cheatsheet

• 02 Nov 12
  

  zstumgoren

  bash reference ***

• 18 Oct 12
  

  Yoon-Wook Kam

  reference Programming

• 28 Sep 12
  

  Steve Houser

  bash reference

• 26 Jun 12
  

  Klaus Mueller

  bash linux reference referenz shell

• 08 Mar 12
  

  bash doc

• 09 Feb 12
  

  papalagi chen
  • The order of expansions is: brace expansion, tilde expansion, parameter, variable, and arithmetic expansion and command substitution (done in a left-to-right fashion), word splitting, and filename expansion.
• 

  vikas pushkar

  "Tran"

• 02 Feb 12
  

  Stefan Lasiewski

  bash sysadmin

• 17 Nov 11
  

  robert jensen

  bash linux reference shell unix manual programming scripting documentation howto

• 09 Nov 11
  

  octavian dumitras

  bash shell command

• 28 Sep 11
  

  Ernst Plüss

  reference manual linux bash scripting script

• 27 Sep 11
  

  Mikhail Golubev

  bash docs linux

• 

  Mike Elliott

  code index shell

• 

  François Georgy

  bash reference programming shell

• 

  Frank Chang

  bash

• 22 Aug 11
  

  yuanye
  • 3.1.1 Shell Operation

  • Enclosing characters in single quotes (‘'’) preserves the literal value of each character within the quotes. A single quote may not occur between single quotes, even when preceded by a backslash.  

      
  • Enclosing characters in double quotes (‘"’) preserves the literal value of all characters within the quotes, with the exception of ‘$’, ‘`’, ‘\’, and, when history expansion is enabled, ‘!’.
  • • Simple Commands: The most common type of command.  
    • Pipelines: Connecting the input and output of several  commands.  
    • Lists: How to execute commands sequentially.  
    • Compound Commands: Shell commands for control flow.  
    • Coprocesses: Two-way communication between commands.
  • [time [-p]] [!] command1 [ [| or |&] command2 ...]

  • If ‘|&’ is used, the standard error of command1 is connected to command2's standard input through the pipe; it is shorthand for 2>&1 |. This implicit redirection of the standard error is performed after any redirections specified by the command.  
  • The reserved word time causes timing statistics to be printed for the pipeline once it finishes.  The statistics currently consist of elapsed (wall-clock) time and user and system time consumed by the command's execution.  The -p option changes the output format to that specified by posix.  The TIMEFORMAT variable may be set to a format string that specifies how the timing information should be displayed.
  • If the pipeline is not executed asynchronously (see Lists), the shell waits for all commands in the pipeline to complete.
  • Each command in a pipeline is executed in its own subshell (see Command Execution Environment). The exit status of a pipeline is the exit status of the last command in the pipeline,
  • If the reserved word ‘!’ precedes the pipeline, the exit status is the logical negation of the exit status as described above.
  • 3.2.3 Lists of Commands
  • If a command is terminated by the control operator ‘&’, the shell executes the command asynchronously in a subshell.

  • An and list has the form 

         command1 && command2 

     

    command2 is executed if, and only if, command1 returns an exit status of zero.  

    An or list has the form 

         command1 || command2 

     

    command2 is executed if, and only if, command1 returns a non-zero exit status.

  • Compound commands are the shell programming constructs.  Each construct begins with a reserved word or control operator and is terminated by a corresponding reserved word or operator.  Any redirections (see Redirections) associated with a compound command apply to all commands within that compound command unless explicitly overridden.  

    Bash provides looping constructs, conditional commands, and mechanisms to group commands and execute them as a unit.
  • If ‘in words’ is not present, the for command executes the commands once for each positional parameter that is set, as if ‘in "$@"’ had been specified

  • Each clause must be terminated with ‘;;’, ‘;&’, or ‘;;&’.  The word undergoes tilde expansion, parameter expansion, command substitution, arithmetic expansion, and quote removal before matching is attempted. Each pattern undergoes tilde expansion, parameter expansion, command substitution, and arithmetic expansion.  
  • An additional binary operator, ‘=~’, is available, with the same precedence as ‘==’ and ‘!=’.  When it is used, the string to the right of the operator is considered an extended regular expression and matched accordingly (as in regex3)).  The return value is 0 if the string matches the pattern, and 1 otherwise.  If the regular expression is syntactically incorrect, the conditional expression's return value is 2.
  • 3.2.4.3 Grouping Commands
  • A function definition may be deleted using the -f option to the unset builtin

  • When a function is executed, the arguments to the function become the positional parameters during its execution (see Positional Parameters).  The special parameter ‘#’ that expands to the number of positional parameters is updated to reflect the change.  Special parameter 0 is unchanged.  The first element of the FUNCNAME variable is set to the name of the function while the function is executing.  

  • All other aspects of the shell execution environment are identical between a function and its caller with these exceptions: the DEBUG and RETURN traps are not inherited unless the function has been given the trace attribute using the declare builtin or the -o functrace option has been enabled with the set builtin, (in which case all functions inherit the DEBUG and RETURN traps), and the ERR trap is not inherited unless the -o errtrace shell option has been enabled.  See Bourne Shell Builtins, for the description of the trap builtin.  
  • Variables local to the function may be declared with the local builtin. These variables are visible only to the function and the commands it invokes.
  • Function names and definitions may be listed with the -f option to the declare or typeset builtin commands (see Bash Builtins).  The -F option to declare or typeset will list the function names only (and optionally the source file and line number, if the extdebug shell option is enabled).  Functions may be exported so that subshells automatically have them defined with the -f option to the export builtin (see Bourne Shell Builtins).  Note that shell functions and variables with the same name may result in multiple identically-named entries in the environment passed to the shell's children.  Care should be taken in cases where this may cause a problem.

  • A positional parameter is a parameter denoted by one or more digits, other than the single digit 0. Positional parameters are assigned from the shell's arguments when it is invoked, and may be reassigned using the set builtin command.  Positional parameter N may be referenced as ${N}, or as $N when N consists of a single digit.  Positional parameters may not be assigned to with assignment statements.  The set and shift builtins are used to set and unset them (see Shell Builtin Commands).  The positional parameters are temporarily replaced when a shell function is executed (see Shell Functions).  

    When a positional parameter consisting of more than a single digit is expanded, it must be enclosed in braces.  

      
  • A parameter is an entity that stores values.  It can be a name, a number, or one of the special characters listed below.  A variable is a parameter denoted by a name.  A variable has a value and zero or more attributes.  Attributes are assigned using the declare builtin command (see the description of the declare builtin in Bash Builtins).
  • A parameter is set if it has been assigned a value. The null string is a valid value. Once a variable is set, it may be unset only by using the unset builtin command.
  • The order of expansions is: brace expansion, tilde expansion, parameter, variable, and arithmetic expansion and command substitution (done in a left-to-right fashion), word splitting, and filename expansion.

  • xpansion and command substitution.  

    Only brace expansion, word splitting, and filename expansion can change the number of words of the expansion; other expansions expand a single word to a single word.  The only exceptions to this are the expansions of "$@" (see Special Parameters) and "${name[@]}" (see Arrays).  

    After all expansions, quote removal (see Quote Removal) is performed.

  • Brace expansions may be nested.  The results of each expanded string are not sorted; left to right order is preserved.  For example, 

         bash$ echo a{d,c,b}e      ade ace abe 

     

    A sequence expression takes the form {x..y[..incr]}, where x and y are either integers or single characters, and incr, an optional increment, is an integer.

  • This construct is typically used as shorthand when the common prefix of the strings to be generated is longer than in the above example: 

         mkdir /usr/local/src/bash/{old,new,dist,bugs} 

     

    or 

         chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}} 

     

      
  • the characters in the tilde-prefix following the tilde are treated as a possible login name.  If this login name is the null string, the tilde is replaced with the value of the HOME shell variable.
  • If the tilde-prefix is ‘~+’, the value of the shell variable PWD replaces the tilde-prefix.  If the tilde-prefix is ‘~-’, the value of the shell variable OLDPWD, if it is set, is substituted.
  • ~

    The value of $HOME 
    

    ~/foo

    $HOME/foo  
    

    ~fred/foo

    The subdirectory foo of the home directory of the user fred  
    

    ~+/foo

    $PWD/foo  
    

    ~-/foo

    ${OLDPWD-'~-'}/foo  
    

    ~N

    The string that would be displayed by ‘dirs +N’  
    

    ~+N

    The string that would be displayed by ‘dirs +N’  
    

    ~-N

    The string that would be displayed by ‘dirs -N’
  • 3.5.3 Shell Parameter Expansion
  • The basic form of parameter expansion is ${parameter}.  The value of parameter is substituted. The braces are required when parameter is a positional parameter with more than one digit, or when parameter is followed by a character that is not to be interpreted as part of its name.
  • The command substitution $(cat file) can be replaced by the equivalent but faster $(< file).
  • The shell scans the results of parameter expansion, command substitution, and arithmetic expansion that did not occur within double quotes for word splitting.
  • After word splitting, unless the -f option has been set (see The Set Builtin), Bash scans each word for the characters ‘*’, ‘?’, and ‘[’.  If one of these characters appears, then the word is regarded as a pattern, and replaced with an alphabetically sorted list of file names matching the pattern.
  • When a pattern is used for filename expansion, the character ‘.’ at the start of a filename or immediately following a slash must be matched explicitly, unless the shell option dotglob is set.  When matching a file name, the slash character must always be matched explicitly.  In other cases, the ‘.’ character is not treated specially.
  • Pattern Matching
  • *

    Matches any string, including the null string.  When the globstar shell option is enabled, and ‘*’ is used in a filename expansion context, two adjacent ‘*’s used as a single pattern will match all files and zero or more directories and subdirectories.  If followed by a ‘/’, two adjacent ‘*’s will match only directories and subdirectories.  
    

    ?

    Matches any single character.
  • Matches any one of the enclosed characters. A pair of characters separated by a hyphen denotes a range expression; any character that sorts between those two characters, inclusive, using the current locale's collating sequence and character set, is matched. If the first character following the ‘[’ is a ‘!’ or a ‘^’ then any character not enclosed is matched. A ‘−’ may be matched by including it as the first or last character in the set. A ‘]’ may be matched by including it as the first character in the set.

  • Within ‘[’ and ‘]’, character classes can be specified using the syntax [:class:], where class is one of the following classes defined in the posix standard: 

              alnum   alpha   ascii   blank   cntrl   digit   graph   lower           print   punct   space   upper   word    xdigit
  • After the preceding expansions, all unquoted occurrences of the characters ‘\’, ‘'’, and ‘"’ that did not result from one of the above expansions are removed.
  • The following redirection operators may precede or appear anywhere within a simple command or may follow a command.  Redirections are processed in the order they appear, from left to right.

  • Note that the order of redirections is significant. For example, the command 

         ls > dirlist 2>&1 

     

    directs both standard output (file descriptor 1) and standard error (file descriptor 2) to the file dirlist, while the command 

         ls 2>&1 > dirlist
  • If the redirection operator is ‘>|’, or the redirection operator is ‘>’ and the noclobber option is not enabled, the redirection is attempted even if the file named by word exists.

  • The general format for appending output is: 

         [n]>>word

  • 3.6.4 Redirecting Standard Output and Standard Error

      

    This construct allows both the standard output (file descriptor 1) and the standard error output (file descriptor 2) to be redirected to the file whose name is the expansion of word.  

    There are two formats for redirecting standard output and standard error: 

         &>word 

     

    and 

         >&word 

     

    Of the two forms, the first is preferred.  This is semantically equivalent to 

         >word 2>&1

  • This is semantically equivalent to 

         >>word 2>&1
  • No parameter expansion, command substitution, arithmetic expansion, or filename expansion is performed on word. If any characters in word are quoted, the delimiter is the result of quote removal on word, and the lines in the here-document are not expanded.  If word is unquoted, all lines of the here-document are subjected to parameter expansion, command substitution, and arithmetic expansion. In the latter case, the character sequence  ewline is ignored, and ‘\’ must be used to quote the characters ‘\’, ‘$’, and ‘`’.

  49 more annotations...

• 18 Aug 11
  

  At Look

  Android-Dev-Reference Android-Dev-Setup

• 05 Aug 11
  

  code4rain

  bash linux reference manual programming scripting

• 06 Jun 11
  

  djroze

  linux bash shell reference manual unix

• 01 Jun 11
  

  Jonathan Bispo

  shell_script

• 31 May 11
  

  kevinmullet
• 17 May 11
  

  r3d33m3r

  programming UNIX_|_Linux BASH manuals string_manipulation arguments

• 25 Mar 11
  

  Alexander A.

  linux bash docu

• 

  woshisl
• 08 Mar 11
  

  Marcin Kasperski

  bash reference

• 23 Feb 11
  

  borislv

  bash official gnu linux shell manual

• 22 Feb 11
  

  scott k

  linux school reference manual unix programming scripting shell bash

• 19 Feb 11
  

  xishen

  linux coding

• 18 Feb 11
  

  Hisashi Nishioka

  bash linux shellscript GNU

• 25 Jan 11
  

  Valentin Pimenov

  bash linux reference

• 18 Jan 11
  

  Thanasis Karathanos

  Το manual για προγραμματισμό στο shell

  bash shell manual scripting

• 15 Jan 11
  

  mom2twinzz

  computer linux reference programming

• 08 Dec 10
  

  Guy Fawkes

  This text is a brief description of the features that are present in the Bash shell

  bash shell

• 04 Dec 10
  

  dancecodes

  bash linux reference shell unix manual programming scripting gnu lvl9 me:icio

• 03 Dec 10
  

  Merry Kidby

  Bash Reference Manual

• 25 Nov 10
  

  Milan Gherga

  bash tutorial reference guide

• 11 Nov 10
  

  Sarab Pannu

  bash

• 29 Oct 10
  

  Sam

  linux bash command shell reference

• 28 Oct 10
  

  krpalospo

  bash linux reference

• 

  Pink Frost

  bash reference manual

• 06 Oct 10
  

  joeltristani

  Linux Bash Reference

• 21 Sep 10
  

  murzzz

  bash linux reference shell scripting ubuntu

• 22 Aug 10
  

  Marc Dupre

  ubuntu bash manual

• 02 Aug 10
  

  blcham

  completion bash

• 20 Jun 10
  

  pietro spagnulo

  bash tutorial

• 15 Jun 10
  

  Luis Blackaller

  Bash Reference Manual code shell

• 05 Jun 10
  

  dvdesigns1099

  CLIMagic

• 27 May 10
  

  vtchernev

  bash

• 30 Apr 10
  

  wuduoyi

  bash reference

• 22 Mar 10
  

  Simon Reavely

  bash reference shell scripting manual

• 02 Feb 10
  

  kave aryan
  • uilding blocks': commands, contro
  • or words to the shell. Quoting can be used to d
  • treatment for special chara

  1 more annotation...

• 26 Jan 10
  

  Roger TM

  Bash Manuales GNU_Linux linux shell manual for:@twitter

• 14 Jan 10
  

  Thomas Larkin

  tech Mac_Stuff bash

• 21 Dec 09
  

  JongGwan Do

  linux bash Manual

• 23 Nov 09
  

  Cuong Nguyen

  Research Programming

• 29 Sep 09
  

  matthewlmcclure

  bash documentation manual gnu

• 22 Sep 09
  

  Kenyth Zeng

  linux shell reference manual scripting bash athand unix programming starred

  • The preamble is prefixed to each string contained within the braces, and the postscript is then appended to each resulting string, expanding left to right.
• 17 Sep 09
  

  linux

• 14 Sep 09
  

  Tony Zhang

  tech

• 12 Sep 09
  

  David Greenberg

  LINUX_BASH

• 25 Aug 09
  

  Shawn Skriver

  shell bash linux reference scripting gnu delicious

• 22 Aug 09
  

  Chandrasekar Ravoori

  bash reference

• 14 Aug 09
  

  Luciano Coelho

  bash programming

• 02 Jul 09
  

  Stephen Camp

  bash linux reference

  • 3.4.2 Special Parameters

      

     The shell treats several parameters specially. These parameters may only be referenced; assignment to them is not allowed.  
  • Positional parameters are assigned from the shell's arguments when it is invoked
• 16 Apr 09
  

  yshlin

  programming reference linux tools bash

• 06 Apr 09
  

  Alberto Acosta

  bash unix

• 25 Mar 09
  

  Denis Ng

  Bash manual at gnu.org

  reference shell programming Linux BASH

Would you like to comment?

Join Diigo for a free account, or sign in if you are already a member.