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Bash Scripting Quick Reference
==========================================
BASH SCRIPTING ==========================================
========================================== TEST COMMAND
==========================================
Invoke: bash [options] file
Shebang: #!/usr/bin/env bash Test: test expression
In script: [ expression ]
========================================== Alternate: [[ espression ]]
LOOP Does not split string words
========================================== Does not expand pathglobs*
for i in <list>; do echo $i; done Expressions:
True: [ expression ]
<list>: False: [! expression ]
FileSpec: *.txt Value: [ (expression) ]
Set: 1 2 3 4 5 And: [ exp1 -a exp2 ] No Short
Range: {start..end} {1..5} Or: [ exp1 -o exp2 ] Circuit
{start..end..increment} Regex: [[ value =~ regex ]]
Variable: $words "w1 w2 w3" regex w/out ": ^as.*$
Arguments: $* or variable : $regex
Command: `command args`
Comparisons:
Each args: String: str1 op str2
for arg; do echo $arg; done "$s1" op "$s2"
Op: == = != < >
------------------------------------------ Numerical: num1 op num2
Op: -eq -ne -lt -le -gt -ge
for (( exp1; exp2; exp3 )) Pattern [[ "str1" == str* ]]
for (( i=1; i<=5; i++ ))
for ((i=1, j=10; i<=5 ; i++, j=j+5)) Empty: -z string Zero-len.
for (( ; ; )) Infinite! Not Empty: -n string
------------------------------------------ File Tests:
Exists: -e file
While: while [ test ]; do Is File: -f file
commands Is Dir: -d file
done Writable: -w file
Infinite: while : ... Terminal: -t FD Std*
Until: until [ test ]; do More: man test
commands
done ==========================================
PATTERNS & FILE GLOBS & REGULAR EXPRESSION
------------------------------------------ ==========================================
Exit loop: break Pattern: (not extended regular expression)
Next: continue Any: *
Start/End: *end start*
========================================== Single: ?
CONDITTIONAL Special: \x
========================================== Brackets: [...]
Set: [chars]
Syntax: Range: [char-char]
if [ tests... ]; Class: [[:class:]]
then <commands>; Not in: [^chars]
elif [ tests... ]; then <cmds>; Alternate:(exp|exp)
else <commands>;
fi Extended REGEX for grep and "test =~":
Character: [chars]
1 Line: [ test ] && ( commands ) Char Range:[char-char]
Unless: [ test ] || ( commands ) Any Char: .
Repetition:* + ? {n}
Case: case value in use "$var" Anchors ^ $
pattern) commands ;; Escape: \char
*) commands ;; else Alternate: (exp|exp)
esac
See "Patterns" and "Test command" ==========================================
TEXT MANIPULATION
========================================== ==========================================
FILE PROCESSING
========================================== Length: ${#var}
Substring: ${var:start:len} first=0
Read STDIN: while read varname; do... ${var:start} to end
Filename: while read varname; do
statements... Default: ${var-default} ${var:-default}
done < $filename Can be: literal, $var, `cmd`
Set to Default: ${var=default}
Slurp: var=`cat $filename` Like: $var = ${var-default}
Alternate: ${var+alt_value}
ReplaceFile: echo $data > $file Like: $var ? alt_value : ""
Truncate: echo -n "" > $file Die: ${var?errmsg}
Or: truncate -s 0 $file Like: die errmsg unless $var
Write/Append: echo $line >> $file
Strip Lead: ${var#Pattern} shortest
${var##Pattern} longest
String End: ${var%Pattner} shortest
${var%%`attern} longest
Replace: ${var/Pattern/Replace}
Global: ${var//Pattern/Replace}
Prefix: ${var/#Pattern/Replace}
Suffix: ${var/%Pattern/Replace}
Variable globbing, returns matching varnames
Prefix: ${!varprefix*} ${!varprefix@}
Ex: for var in ${!namespace*}; ...
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