Bash conditions and flow control

Updated 29 October 2024

ToDO

bash

- switch statement in conditions and flow control

Numeric conditions

Condition	Description
[[ INTERGER1 -eq INTEGER2 ]]	INTEGER1 is equal to INTEGER2
[[ INTEGER1 -ne INTEGER2 ]]	INTEGER1 is not equal to INTEGER2
[[ INTEGER1 -lt INTEGER ]]	INTEGER1 is less than INTEGER2
[[ INTEGER1 -le INTEGER2 ]]	INTEGER1 is less than or equal to INTEGER2
[[ INTEGER1 -gt INTEGER2 ]]	INTEGER1 is greater than INTEGER2
[[ INTERGER1 -ge INTEGER2 ]]	INTEGER1 is greater than or equal to INTEGER2
(( INTEGER1 < INTEGER2 ))	INTEGER1 is less than INTEGER2
(( INTEGER1 <= INTEGER2 ))	INTEGER1 is less than INTEGER2
(( INTEGER1 > INTEGER2 ))	INTEGER1 is greater than INTEGER2
(( INTEGER1 >= INTEGER2 ))	INTEGER1 is greater than or equal to INTEGER2
(( INTEGER1 == INTEGER2 ))	INTEGER1 is equal to INTEGER2
(( INTEGER1 != INTEGER2 ))	INTEGER1 is not equal to INTEGER2

String conditions

Condition	Description
[[ -z STR ]]	Empty string
[[ -n STR ]]	Not empty string
[[ STR == STR ]]	Equal
[[ STR = STR ]]	Equal (Same above)
[[ STR < STR ]]	Less than (ASCII)
[[ STR > STR ]]	Greater than (ASCII)
[[ STR != STR ]]	Not Equal
[[ STR =~ REGEXP ]]	Regexp

More conditions

Condition	Description
[[ -o noclobber ]]	If OPTION is enabled.
EXPR	expression is true
! EXPR	negate expression

File conditions

Condition	Expression
[[ -b FILE ]]	FILE exists and is block special
[[ -c FILE ]]	FILE exists and is character special
[[ -d FILE ]]	FILE exists and is a directory
[[ -e FILE ]]	FILE exists
[[ -f FILE ]]	FILE exists and is a regular file
[[ -g FILE ]]	FILE exists and is set-group-ID
[[ -G FILE ]]	FILE exists and is owned by the effective group ID
[[ -h FILE ]]	FILE exists and is a symbolic link (same as -L)
[[ -k FILE ]]	FILE exists and has its sticky bit set
[[ -L FILE ]]	FILE exists and is a symbolic link (same as -h)
[[ -N FILE ]]	FILE exists and has been modified since it was last read
[[ -O FILE ]]	FILE exists and is owned by the effective user ID
[[ -p FILE ]]	FILE exists and is a named pipe
[[ -r FILE ]]	FILE exists and the user has read access
[[ -s FILE ]]	FILE exists and has a size greater than zero
[[ -S FILE ]]	FILE exists and is a socket
[[ -t FD ]]	file descriptor FD is opened on a terminal
[[ -u FILE ]]	FILE exists and its set-user-ID bit is set
[[ -w FILE ]]	FILE exists and the user has write access
[[ -x FILE ]]	FILE exists and the user has execute (or search) access
[[ FILE1 -nt FILE2 ]]	FILE1 is newer (modification date) than FILE2
[[ FILE1 -ot FILE2 ]]	FILE1 is older than FILE2
[[ FILE1 -ef FILE2 ]]	FILE1 and FILE2 have the same device and inode numbers or both files are the same

Compound conditions

Condition	Description
[[ condition1 ]] && [[ condition2 ]]	Evaluate to True if both conditions are TRUE
[[ condition1 ]] \|\| [[ condition2 ]]	Evaluate to True if either one of the conditions TRUE
[ condition1 -a condition2 ]	Evaluate to True if both conditions are TRUE
[ condition1 -o condition2 ]	Evaluate to True if either one of the conditions TRUE

Note: It is worth mentioning that you can replace all the double square brackets with single square brackets for example : [[ NUM -eq NUM ]] can also be written as [ NUM -eq NUM ] . This works with all the all conditions except for compound conditions which uses -a (AND) and -o (OR) as logical operators.

Advanced if-then Features

Single parentheses (.......) allow you to use subshells in your if statement comparisons.
The double parentheses (( epression )) command allows you to incorporate advanced mathematical formulas in your comparisons. check out performing arithmetic operations.
The double bracket [[.......]] command provides advanced features for string comparisons.

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⚙️Bash conditions and flow control