shell_comparison.md

String operator

Operator	Description	Example
=	is equal to	[ $a = $b ]
==	is equal to	[ $a == $b ]
!=	is not equal to	[ $a != $b ]
>	is greater than, in alphabetical order	[ $a > $b ]
<	is less than, in alphabetical order	[ $a < $b ]
-z	has zero length	[ -z $a ]
-n	has non-zero length	[ -n $a ]
str	is not an empty string	[ $a ]

Integer operator

Operator	Description	Example
-eq	is equal to	[ $a -eq $b ]
-ne	is not equal to	[ $a -ne $b ]
-gt	is greater than	[ $a -gt $b ]
-ge	is greater than or equal to	[ $a -ge $b ]
-lt	is less than	[ $a -lt $b ]
-le	is less than or equal to	[ $a -le $b ]
>	is greater than	(( $a > $b ))
=>	is greater than or equal to	(( $a >= $b ))
<	is less than	(( $a < $b ))
<=	is less than or equal to	(( $a <= $b ))

Boolean operator

Operator	Description	Example
!	logic NOT	[ ! $a ]
-o	logic OR	[ $a -lt 20 -o $b -gt 100 ]
-a	logic AND	[ $a -lt 20 -a $b -gt 100 ]

File test operator

Operator	Description	Example
-b file	checks if file is a block special file	[ -b file ]
-c file	checks if file is a character special file	[ -c file ]
-d file	checks if file is a directory	[ -d file ]
-f file	checks if file is an ordinary file	[ -f file ]
-g file	checks if file has its set group ID (SGID) bit set	[ -g file ]
-k file	checks if file has its sticky bit set	[ -k file ]
-p file	checks if file is a named pipe	[ -p file ]
-t file	checks if file descriptor is open and associated with a terminal	[ -t file ]
-u file	checks if file has its Set User ID (SUID) bit set	[ -u file ]
-r file	checks if file is readable	[ -r file ]
-w file	checks if file is writable	[ -w file ]
-x file	checks if file is executable	[ -x file ]
-s file	checks if file has size greater than 0	[ -s file ]
-e file	checks if file exists	[ -e file ]