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If test is invoked as [, then it requires a closing bracket ] as its last argument. Otherwise, there must be no closing bracket.
test understands the following expressions, among others:
- -e filename
- True if filename exists.
- -d filename
- True if filename exists and is a directory.
- -f filename
- True if filename exists and is a plain file.
- -h filename
- True if filename exists and is a symbolic link.
- -r filename
- True if filename exists and is readable.
- -w filename
- True if filename exists and is writable.
- -n string
- True if the length of string is non-zero.
- -z string
- True if the length of string is zero.
- string
- True if string is not the empty string.
- s1 = s2
- True if the strings s1 and s2 are identical.
- s1 != s2
- True if the strings s1 and s2 are not identical.
- n1 -eq n2
- True if the numbers n1 and n2 are equal.
- n1 -ne n2
- True if the numbers n1 and n2 are not equal.
- n1 -gt n2
- True if the number n1 is greater than n2.
- n1 -ge n2
- True if the number n1 is greater than or equal to n2.
- n1 -lt n2
- True if the number n1 is less than n2.
- n1 -le n2
- True if the number n1 is less than or equal to n2.
- ! expression
- Negates expression, that is, returns true iff expression is false.
- expr1 -a expr2
- True if both expressions, expr1 and expr2 are true.
- expr1 -o expr2
- True if either expression, expr1 or expr2 is true.
- ( expression )
- True if expression is true. This allows one to nest expressions.
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