Condition evaluation.
Evaluate an expression and, if it evaluates to true, return a zero (true) exit
status; otherwise return 1 (false). If there is no expression, test also returns
1 (false).
Syntax
test expression
[ expr ]
Key
The following primaries are used to construct expression:
-a file True if file exists.
-b file True if file exists and is a block special file.
-c file True if file exists and is a character special file.
-d file True if file exists and is a directory.
-e file True if file exists (regardless of type).
-f file True if file exists and is a regular file.
-g file True if file exists and its set group ID flag is set.
-h 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.
-k file True if file exists and its sticky bit is set.
-n string True if the length of string is nonzero.
-p file True if file is a named pipe (FIFO).
-r file True if file exists and is readable.
-s file True if file exists and has a size greater than zero.
-t fd True if file descriptor fd is open and refers to a terminal.
-u file True if file exists and its set user ID flag is set.
-w 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.
-x 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.
-z string True if the length of string is zero.
-L file True if file exists and is a symbolic link.
-O file True if file exists and its owner matches the effective us-
er id of this process.
-G file True if file exists and its group matches the effective
group id of this process.
-S file True if file exists and is a socket.
file1 -nt file2
True if file1 exists and is newer than file2.
file1 -ot file2
True if file1 exists and is older than file2.
file1 -ef file2
True if file1 and file2 exist and refer to the same file.
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 ASCII value
of their characters.
s1 > s2 True if string s1 comes after s2 based on the ASCII value
of their characters.
s1 True if s1 is not the null string.
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 inte-
ger n2.
n1 -le n2 True if the integer n1 is algebraically less than or equal
to the integer n2.
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.
test 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.
test and [ evaluate conditional expressions using a set of rules based on the number of arguments:
0 arguments - The expression is false.
1 argument - The expression is true if and only if the argument is not null.
2 arguments - If the first argument is !, the expression is true if and only if the second argument is null. If the first argument is one of the unary conditional operators listed above, the expression is true if the unary test is true. If the first argument is not a valid unary conditional operator, the expression is false.
3 arguments - If the second argument is one of the binary conditional operators listed above, the result of the expression is the result of the binary test using the first and third arguments as operands.
If the first argument is !, the value is the negation of the two-argument test using the second and third arguments.
If the first argument is exactly ( and the third argument is exactly ), the result is the one-argument test of the second argument. Otherwise, the expression is false. The -a and -o operators are considered binary operators in this case.
4 arguments - If the first argument is !, the result is the negation of the three-argument expression composed of the remaining arguments. Otherwise, the expression is parsed and evaluated according to precedence using the rules listed above.
5 or more arguments - The expression is parsed and evaluated according to precedence using the rules listed above.
Examples
$ test -a DemoFile.txt
$ echo $?
0
$ test -a NonExistentFile.txt
$ echo $?
1
$ test -n "Some sample text"
$ echo $?
0
test is a bash built in command.
“The test of a vocation is the love of the drudgery it involves” - Logan Pearsall
Related:
test man page - Apple.com
eval - Evaluate several commands/arguments
expr - Evaluate expressions
