TEST(1) General Commands Manual TEST(1)

test, [ — condition evaluation utility

test expression

[ expression ]

The test utility evaluates the expression and, if it evaluates to true, returns a zero (true) exit status; otherwise it returns 1 (false). If there is no expression, test also returns 1 (false).

All operators and flags are separate arguments to the test utility.

When checking file, one should consider TOCTOU race-conditions. Avoiding the issue altogether with directly using file instead is strongly recommended.

The following primaries are used to construct expression:

file
True if file exists and is a block special file.
file
True if file exists and is a character special file.
file
True if file exists and is a directory.
file
True if file exists (regardless of type).
file1 -ef file2
True if file1 and file2 exist and refer to the same file.
file
True if file exists and is a regular file.
file
True if file exists and its set group ID flag is set.
file
True if file exists and is a symbolic link. This operator is retained for compatibility with previous versions of this program. Do not rely on its existence; use -L instead.
file
True if file exists and is a symbolic link.
file
True if file exists and its sticky bit is set.
string
True if the length of string is nonzero.
file1 -nt file2
True if file1 exists and is newer than file2.
file1 -ot file2
True if file1 exists and is older than file2.
file
True if file is a named pipe (FIFO).
file
True if file exists and is readable.
file
True if file exists and is a socket.
file
True if file exists and has a size greater than zero.
file_descriptor
True if the file whose file descriptor number is file_descriptor is open and is associated with a terminal.
file
True if file exists and its set user ID flag is set.
file
True if file exists and is writable. True indicates only that the write flag is on. The file is not writable on a read-only file system even if this test indicates true.
file
True if file exists and is executable. True indicates only that the execute flag is on. If file is a directory, true indicates that file can be searched.
string
True if the length of string is zero.
file
True if file exists and its owner matches the effective user id of this process.
file
True if file exists and its group matches the effective group id of this process.
string
True if string is not the null string.
s1 = s2
True if the strings s1 and s2 are identical.
s1 != s2
True if the strings s1 and s2 are not identical.
s1 < s2
True if string s1 comes before s2 based on the binary value of their characters.
s1 > s2
True if string s1 comes after s2 based on the binary value of their characters.
n1 -eq n2
True if the integers n1 and n2 are algebraically equal.
n1 -ne n2
True if the integers n1 and n2 are not algebraically equal.
n1 -gt n2
True if the integer n1 is algebraically greater than the integer n2.
n1 -ge n2
True if the integer n1 is algebraically greater than or equal to the integer n2.
n1 -lt n2
True if the integer n1 is algebraically less than the integer n2.
n1 -le n2
True if the integer n1 is algebraically less than or equal to the integer n2.

If file is a symbolic link, test will fully dereference it and then evaluate the expression against the file referenced, except for the -h and -L primaries.

These primaries can be combined with the following operators:

expression
True if expression is false.
expression1 -a expression2
True if both expression1 and expression2 are true.
expression1 -o expression2
True if either expression1 or expression2 are true.
expression )
True if expression is true.

The -a operator has higher precedence than the -o operator.

Some shells may provide a builtin test command which is similar or identical to this utility. Consult the builtin(1) manual page.

The test grammar is inherently ambiguous. In order to assure a degree of consistency, the cases described in the IEEE Std 1003.2 (“POSIX.2”), section D11.2/4.62.4, standard are evaluated consistently according to the rules specified in the standards document. All other cases are subject to the ambiguity in the command semantics.

In particular, only expressions containing -a, -o, ( or ) can be ambiguous.

The test utility exits with one of the following values:

0
expression evaluated to true.
1
expression evaluated to false or expression was missing.
>1
An error occurred.

Implement test FILE1 -nt FILE2 using only POSIX functionality:

test -n "$(find -L -- FILE1 -prune -newer FILE2 2>/dev/null)"

This can be modified using non-standard find(1) primaries like -newerca to compare other timestamps.

For compatibility with some other implementations, the = primary can be substituted with == with the same meaning.

builtin(1), expr(1), find(1), sh(1), stat(1), symlink(7)

test should be compliant with the IEEE Std 1003.1-2024 (“POSIX.1”) specification.

The primaries ==, -G, and -O are extensions. The -a, -o binary primaries, and ‘(’ and ‘)’ operators are kept for backward compatibility but should be taken as deprecated.

A test utility appeared in Version 7 AT&T UNIX.

Both sides are always evaluated in -a and -o. For instance, the writable status of file will be tested by the following command even though the former expression indicated false, which results in a gratuitous access to the file system:

[ -z abc -a -w file ]
To avoid this, write
[ -z abc ] && [ -w file ]
October 5, 2016 Linux 6.6.67-gentoo-x86_64