integer comparison
- -eq
- is equal to
if [ "$a" -eq "$b" ]
- -ne
- is not equal to
if [ "$a" -ne "$b" ]
- -gt
- is greater than
if [ "$a" -gt "$b" ]
- -ge
- is greater than or equal to
if [ "$a" -ge "$b" ]
- -lt
- is less than
if [ "$a" -lt "$b" ]
- -le
- is less than or equal to
if [ "$a" -le "$b" ]
- <
- is less than (within double parentheses)
(("$a" < "$b"))
- <=
- is less than or equal to (within double parentheses)
(("$a" <= "$b"))
- >
- is greater than (within double parentheses)
(("$a" > "$b"))
- >=
- is greater than or equal to (within double parentheses)
(("$a" >= "$b"))
- =
-
is equal to
if [ "$a" = "$b" ]
Note the whitespace framing the =. if [ "$a"="$b" ] is not equivalent to the above.
- ==
- is equal to
if [ "$a" == "$b" ]
This is a synonym for =.
The == comparison operator behaves differently within a double-brackets test than within single brackets. [[ $a == z* ]] # True if $a starts with an "z" (pattern matching). [[ $a == "z*" ]] # True if $a is equal to z* (literal matching). [ $a == z* ] # File globbing and word splitting take place. [ "$a" == "z*" ] # True if $a is equal to z* (literal matching). # Thanks, Stéphane Chazelas
- !=
- is not equal to
if [ "$a" != "$b" ]
This operator uses pattern matching within a [[ ... ]] construct.
- <
- is less than, in ASCII alphabetical order
if [[ "$a" < "$b" ]]
if [ "$a" \< "$b" ]
Note that the “<” needs to be escaped within a [ ] construct.
- >
- is greater than, in ASCII alphabetical order
if [[ "$a" > "$b" ]]
if [ "$a" \> "$b" ]
Note that the “>” needs to be escaped within a [ ] construct.
See Example 27-11 for an application of this comparison operator.
- -z
- string is null, that is, has zero length
String='' # Zero-length ("null") string variable. if [ -z "$String" ] then echo "\$String is null." else echo "\$String is NOT null." fi # $String is null. - -n
- string is not null.
The -n test requires that the string be quoted within the test brackets. Using an unquoted string with ! -z, or even just the unquoted string alone within test brackets (see Example 7-6) normally works, however, this is an unsafe practice. Always quote a tested string. [1]