Test Operators (Learning the Korn Shell, 2nd Edition)

B.5. Test Operators

These are the operators that are used with the [[...]] construct. They can be logically combined with && ("and") and || ("or") and grouped with parenthesis. When used with filenames of the form /dev/fd/N, they test the corresponding attribute of open file descriptor N.

Operator	True if...
`-a` `file`	file exists. (Obsolete. `-e` is preferred.)
`-b` `file`	file is a block device file.
`-c` `file`	file is a character device file.
`-C` `file`	file is a contiguous file. (Not for most Unix versions.)
`-d` `file`	file is a directory.
`-e` `file`	file exists.
`-f` `file`	file is a regular file.
`-g` `file`	file has its setgid bit set.
`-G` `file`	file's group ID is the same as the effective group ID of the shell.
`-h` `file`	file is a symbolic link.
`-k` `file`	file has its sticky bit set.
`-l` `file`	file is a symbolic link. (Only works on systems where /bin/test -l tests for symbolic links.)
`-L` `file`	file is a symbolic link.
`-n` `string`	string is non-null.
`-o` `option`	option is set.
`-O` `file`	file is owned by the shell's effective user ID.
`-p` `file`	file is a pipe or named pipe (FIFO file).
`-r` `file`	file is readable.
`-s` `file`	file is not empty.
`-S` `file`	file is a socket.
`-t` `N`	File descriptor N points to a terminal.
`-u` `file`	file has its setuid bit set.
`-w` `file`	file is writable.
`-x` `file`	file is executable, or file is a directory that can be searched.
`-z` `string`	string is null.
`fileA` `-nt fileB`	fileA is newer than fileB, or fileB does not exist.
`fileA` `-ot fileB`	fileA is older than fileB, or fileB does not exist.
`fileA` `-ef fileB`	fileA and fileB point to the same file.
`string` `= pattern`	string matches pattern (which can contain wildcards). Obsolete; `==` is preferred.
`string` `== pattern`	string matches pattern (which can contain wildcards).
`string` `!= pattern`	string does not match pattern.
`stringA` `< stringB`	stringA comes before stringB in dictionary order.
`stringA` `> stringB`	stringA comes after stringB in dictionary order.
`exprA` `-eq exprB`	Arithmetic expressions exprA and exprB are equal.
`exprA` `-ne exprB`	Arithmetic expressions exprA and exprB are not equal.
`exprA` `-lt exprB`	exprA is less than exprB.
`exprA` `-gt exprB`	exprA is greater than exprB.
`exprA` `-le exprB`	exprA is less than or equal to exprB.
`exprA` `-ge exprB`	exprA is greater than or equal to exprB.

The operators -eq, -ne, -lt, -le, -gt, and -ge are considered obsolete in ksh93; the let command or ((...)) should be used instead.

For =, ==, and !=, quote pattern to do literal string comparisons.