16.3 test: Check file types and compare values

test returns a status of 0 (true) or 1 (false) depending on the evaluation of the conditional expression expr. Each part of the expression must be a separate argument.

test has file status checks, string operators, and numeric comparison operators.

test has an alternate form that uses opening and closing square brackets instead a leading ‘test’. For example, instead of ‘test -d /’, you can write ‘[ -d / ]’. The square brackets must be separate arguments; for example, ‘[-d /]’ does not have the desired effect. Since ‘test expr’ and ‘[ expr ]’ have the same meaning, only the former form is discussed below.


test expression
[ expression ]
[ ]
[ option

Due to shell aliases and built-in test functions, using an unadorned test interactively or in a script may get you different functionality than that described here. Invoke it via env (i.e., env test …) to avoid interference from the shell.

If expression is omitted, test returns false. If expression is a single argument, test returns false if the argument is null and true otherwise. The argument can be any string, including strings like ‘-d’, ‘-1’, ‘--’, ‘--help’, and ‘--version’ that most other programs would treat as options. To get help and version information, invoke the commands ‘[ --help’ and ‘[ --version’, without the usual closing brackets. See Common options.

Exit status:

0 if the expression is true,
1 if the expression is false,
2 if an error occurred.
File type tests    -[bcdfhLpSt]
Access permission tests    -[gkruwxOG]
File characteristic tests    -e -s -nt -ot -ef
String tests    -z -n = == !=
Numeric tests    -eq -ne -lt -le -gt -ge
Connectives for test    ! -a -o