GNU Bash

Overview

Bash is the shell, or command language interpreter, for the gnu operating system. The name is an acronym for the ‘Bourne-Again SHell’, a pun on Stephen Bourne, the author of the direct ancestor of the current Unix shell sh, which appeared in the Seventh Edition Bell Labs Research version of Unix.

All of the Bourne shell builtin commands are available in Bash, The rules for evaluation and quoting are taken from the posix specification for the ‘standard’ Unix shell.

Commands

Builtin

• until test-commands; do consequent-commands; done
• select name [in words …]; do commands; done
• ((…))
• [[…]]

• getopts optstring name [arg …]
• hash [-r] [-p filename] [-dt] [name]
• pwd [-LP]
• return [n]
• test expr
• umask [-p] [-S] [mode]
• unset [-fnv] [name]

• alias [-p] [name[=value] …]
• bind
  • bind [-m keymap] [-lpsvPSVX]
  • bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename
  • bind [-m keymap] -x keyseq:shell-command
  • bind [-m keymap] keyseq:function-name
  • bind [-m keymap] keyseq:readline-command
  • bind readline-command-line
• builtin [shell-builtin [args]]
• caller [expr]
• command [-pVv] command [arguments …]
• declare [-aAfFgiIlnrtux] [-p] [name[=value] …]
• echo [-neE] [arg …]
• enable [-a] [-dnps] [-f filename] [name …]
• help [-dms] [pattern]
• let expression [expression …]
• local [option] name[=value] …
• logout [n]
• mapfile [-d delim] [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [-c quantum] [array]
• printf [-v var] format [arguments]
• read [-ers] [-a aname] [-d delim] [-i text] [-n nchars] [-N nchars] [-p prompt] [-t timeout] [-u fd] [name …]
• readarray [-d delim] [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [-c quantum] [array]
• source filename
• type [-afptP] [name …]
• typeset [-afFgrxilnrtux] [-p] [name[=value] …]
• ulimit
  • ulimit [-HS] -a
  • ulimit [-HS] [-bcdefiklmnpqrstuvxPRT] [limit]
• set
  • set [-abefhkmnptuvxBCEHPT] [-o option-name] [–] [-] [argument …]
  • set [+abefhkmnptuvxBCEHPT] [+o option-name] [–] [-] [argument …]
• shopt [-pqsu] [-o] [optname …]
• dirs [-clpv] [+N | -N]
• popd [-n] [+N | -N]
• pushd [-n] [+N | -N | dir]
• bg [jobspec …]
• fg [jobspec]
• jobs
  • jobs [-lnprs] [jobspec]
  • jobs -x command [arguments]
• kill
  • kill [-s sigspec] [-n signum] [-sigspec] jobspec or pid
  • kill -l|-L [exit_status]
• wait [-fn] [-p varname] [jobspec or pid …]
• disown [-ar] [-h] [jobspec … | pid … ]
• suspend [-f]
• compgen [option] [word]
• complete
  • complete [-abcdefgjksuv] [-o comp-option] [-DEI] [-A action] [- G globpat]
  • [-W wordlist] [-F function] [-C command] [-X filterpat]
  • [-P prefix] [-S suffix] name [name …]
  • complete -pr [-DEI] [name …]
• compopt [-o option] [-DEI] [+o option] [name]
• fc
  • fc [-e ename] [-lnr] [first] [last]
  • fc -s [pat=rep] [command]
• history
  • history [n]
  • history -c
  • history -d offset
  • history -d start-end history [-anrw] [filename] history -ps arg

Coprocesses

• coproc

Functions

• function fname [()] compound-command [ redirections ]

Parameters

• declare -n ref=$1
• 0

Shell Expansions

• brace expansion
• tilde expansion
• parameter and variable expansion • command substitution
• arithmetic expansion
• word splitting
• filename expansion

Variables

• CDPATH
• IFS
• MAIL
• MAILPATH
• OPTARG
• OPTIND
• PATH
• PS1
• PS2

• _

BASH BASHOPTS BASHPID BASH_ALIASES BASH_ARGC BASH_ARGV BASH_ARGV0 BASH_CMDS BASH_CMDS is unset, it loses its special properties, even if it is subsequently reset. BASH_COMMAND BASH_COMPAT BASH_ENV BASH_EXECUTION_STRING BASH_LINENO BASH_LOADABLES_PATH BASH_REMATCH BASH_SOURCE BASH_SUBSHELL BASH_VERSINFO BASH_VERSINFO BASH_VERSINFO BASH_VERSION BASH_XTRACEFD CHILD_MAX COLUMNS COMP_CWORD COMP_LINE COMP_POINT COMP_TYPE COMP_KEY COMP_WORDBREAKS COMP_WORDS COMPREPLY COPROC DIRSTACK EMACS ENV WORDBREAKS EPOCHREALTIME EPOCHSECONDS EUID The numeric effective user id of the current user. This variable is readonly. EXECIGNORE FCEDIT FIGNORE FUNCNAME FUNCNEST GLOBIGNORE GROUPS histchars HISTCMD HISTCONTROL HISTFILE HISTFILESIZE HISTIGNORE HISTSIZE HISTTIMEFORMAT HOSTFILE HOSTNAME HOSTTYPE IGNOREEOF INPUTRC INSIDE_EMACS LANG LC_ALL LC_COLLATE LC_CTYPE LC_MESSAGES LC_NUMERIC LC_TIME LINENO LINES MACHTYPE MAILCHECK MAPFILE OLDPWD OPTERR OSTYPE PIPESTATUS POSIXLY_CORRECT PPID The process id of the shell’s parent process. This variable is readonly. PROMPT_COMMAND PROMPT_DIRTRIM PWD The current working directory as set by the cd builtin. RANDOM Each time this parameter is referenced, it expands to a random integer between 0 and 32767. Assigning a value to this variable seeds the random number gener- ator. If RANDOM is unset, it loses its special properties, even if it is subsequently reset. READLINE_ARGUMENT READLINE_LINE READLINE_MARK READLINE_POINT REPLY SECONDS SHELL SHELLOPTS SHLVL SRANDOM TIMEFORMAT TMOUT TMPDIR If set, Bash uses its value as the name of a directory in which Bash creates temporary files for the shell’s use. UID The numeric real user id of the current user. This variable is readonly.

Redirections

Shell Arithmetic

Misc.

• |& vs 2>&1 |

Resources

• Bash Reference Manual
• Advanced Bash-Scripting Guide
• Google Shell Style Guide