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test, [ - Evaluates conditional expressions
[ expression ]
The test command evaluates an expression constructed of functions and
operators. If the value of expression is true, test returns an exit value
of 0 (zero); otherwise, it returns a nonzero (false) exit value. The test
command also returns a nonzero exit value if there are no arguments.
The alternate form of the command surrounds expression with [ ] (brackets).
When you use this form, you must surround the brackets with spaces.
The test Expressions
All of the listed functions and operators are separate arguments to test.
The following functions are used to construct expression:
TRUE if file exists and has read permission.
TRUE if file exists and has write permission.
TRUE if file exists and has execute permission.
TRUE if file exists and is a regular file.
TRUE if file exists and is a directory.
TRUE if file exists.
TRUE if file exists and is a character-special file.
TRUE if file exists and is a block-special file.
TRUE if file exists and is a named pipe (FIFO).
TRUE if file exists and is a soft link. Synonym for -L.
TRUE if file exists and is a soft link. Synonym for -h.
TRUE if file exists and its set-user ID bit is set.
TRUE if file exists and its set-group ID bit is set.
TRUE if file exists and its sticky bit is set.
TRUE if file exists and has a size greater than 0 (zero).
TRUE if the open file with file descriptor number file_descriptor (1 by
default) is associated with a terminal device.
TRUE if the length of string1 is 0 (zero).
TRUE if the length of string1 is nonzero.
string1 = string2
TRUE if string1 and string2 are identical.
string1 and string2 are not identical.
string1 is not the null string.
number1 -eq number2
TRUE if the integers number1 and number2 are algebraically equal. Any
of the comparisons -ne, -gt, -ge, -lt, and -le can be used in place of
The listed functions can be combined with the following operators:
! Unary negation operator.
-a Binary AND operator.
-o Binary OR operator (-a has higher precedence than -o).
\( expression \)
Parentheses for grouping.
1. To test whether a file exists and is not empty, enter:
if test ! -s "$1"
echo $1 does not exist or is empty.
If the file specified by the first positional parameter to the shell
procedure does not exist, this displays an error message. If $1
exists, it displays nothing. Note that there must be a space between
-s and the filename.
The double quotes around $1 ensure that the test will work properly
even if the value of $1 is the empty string. If the double quotes are
omitted and $1 is the empty string, test displays the error message
test: parameter expected.
2. To do a complex comparison, enter:
if [ $# -lt 2 -o ! -s "$1" ]
If the shell procedure was given fewer than two positional parameters
or the file specified by $1 does not exist, then this exits the shell
procedure. The special shell variable $# represents the number of
positional parameters entered on the command line that started this
The test command evaluates expression and, if its value is TRUE, returns an
exit value of 0; otherwise, it returns a nonzero (FALSE) exit value; the
test command also returns a nonzero exit value if there are no arguments.
Commands: csh(1), find(1), ksh(1), sh(1).