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Bash 4 - a rough overview

The Bash Hackers Wiki

This wiki is intended to hold documentation of any kind about GNU Bash. The main motivation was to provide human-readable documentation and information so users aren't forced to read every bit of the Bash manpage - which can be difficult to understand. However, the docs here are not meant as a newbie tutorial.

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Scripting and general information

Xnxx

Code snippets

There is a section that holds small code snippets.

See also some Bash source code excerpts.

How to....

Doing specific tasks: concepts, methods, ideas:

Bash syntax and operations

Compound commands

Compound commands overview
Grouping
{ …; } command grouping
( … ) command grouping in a subshell
Conditionals
[[ ... ]] conditional expression
if …; then …; fi conditional branching
case … esac pattern-based branching
Loops
for word in …; do …; done classic for-loop
for ((x=1; x<=10; x++)); do ...; done C-style for-loop
while …; do …; done while loop
until …; do …; done until loop
Misc
(( ... )) arithmetic evaluation
select word in …; do …; done user selections

Expansions and substitutions

Introduction to expansions and substitutions
{A,B,C} {A..C} Brace expansion
~/ ~root/ Tilde expansion
$FOO ${BAR%.mp3} Parameter expansion
`command` $(command) Command substitution
<(command) >(command) Process substitution
$((1 + 2 + 3)) $[4 + 5 + 6] Arithmetic expansion
Hello <---> Word! Word splitting
/data/*-av/*.mp? Pathname expansion

Builtin Commands

This is a selection of builtin commands and command-like keywords, loosely arranged by their common uses. These are provided directly by the shell, rather than invoked as standalone external commands.

Declaration commands
Commands that set and query attributes/types, and manipulate simple datastructures. 		Alt Type
declareDisplay or set shell variables or functions along with attributes. typeset builtin
exportDisplay or set shell variables, also giving them the export attribute. typeset -x special builtin
evalEvaluate arguments as shell code. - special builtin
localDeclare variables as having function local scope. - builtin
readonlyMark variables or functions as read-only. typeset -r special builtin
unsetUnset variables and functions. - special builtin
shiftShift positional parameters - special builtin
I/O
Commands for reading/parsing input, or producing/formatting output of standard streams. 		Alt Type
coprocCo-processes: Run a command in the background with pipes for reading / writing its standard streams. - keyword
echoCreate output from arguments. - builtin
mapfileRead lines of input into an array. readarray builtin
printf"advanced echo." - builtin
readRead input into variables or arrays, or split strings into fields using delimiters. - builtin
Configuration and Debugging
Commands that modify shell behavior, change special options, assist in debugging. 		Alt Type
callerIdentify/print execution frames. - builtin
setSet the positional parameters and/or set options that affect shell behaviour. - special builtin
shoptset/get some bash-specific shell options. - builtin
Control flow and data processing
Commands that operate on data and/or affect control flow. 		Alt Type
colon "true" null command. true special builtin
dot Source external files. source special builtin
false Fail at doing nothing. - builtin
continue / break continue with or break out of loops. - special builtin
let Arithmetic evaluation simple command. - builtin
return Return from a function with a specified exit status. - special builtin
[ The classic test simple command. test builtin
Process and Job control
Commands related to jobs, signals, process groups, subshells. 		Alt Type
exec Replace the current shell process or set redirections. - special builtin
exit Exit the shell. - special builtin
kill Send a signal to specified process(es) - builtin
trap Set signal handlers or output the current handlers. - special builtin
times Display process times. - special builtin
wait Wait for background jobs and asynchronous lists. - builtin
Alt Type

previous alphabetical version

A-G
calleridentify/print execution frames (Bash builtin)
coprocCo-processes (Bash keyword)
declaredisplay or set shell variables or functions along with attributes (Bash builtin, synonym: typeset)
exec replace the shell, set redirections (Bash builtin)
I-N
letarithmetic evaluation - an old fashioned way (Bash builtin)
mapfileMapping lines of input to an array, also named readarray (Bash builtin)
O-T
printf"advanced echo" (Bash builtin)
readgetting input from stdin (Bash builtin)
readonlymark variables or functions as read-only (Bash builtin)
setcontrol positional parameters and shell behaviour (Bash builtin)
shoptset/get shell options (Bash builtin)
testthe classic test command (Bash builtin)
U-Z
unsetunset variables and functions (Bash builtin)

Dictionary

A list of expressions, words, and their meanings is here.

Links

Official Bash links

Recommended Shell resources

Documentation / Reference

Assorted interesting links

Bash Libraries (needs review)

Most wanted

Statistics for Month: April 2012
Rank Views Article
1 6833Small getopts tutorial (March: 11663)
2 4025The printf command (March: 7079)
3 2861Quotes and escaping (March: 5730)
4 2854The classic test command (March: 6145)
5 2222Parameter expansion (March: 4540)
6 1760Handling positional parameters (March: 3591)
7 1249Bash 4 - a rough overview (March: –)
8 1212Editing files via scripts with ed (March: 2727)
9 1205The read builtin command (March: –)
10 1182Lock your script (against parallel execution) (March: –)
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  • Last modified: 2021/12/28 08:56
  • by xnxx