test - perform tests on files and text¶
Synopsis¶
test [EXPRESSION]
[ [EXPRESSION] ]
Description¶
Tests the expression given and sets the exit status to 0 if true, and 1 if false. An expression is made up of one or more operators and their arguments.
The first form (test) is preferred. For compatibility with other shells, the second form is available: a matching pair of square brackets ([ [EXPRESSION ] ]).
This test is mostly POSIX-compatible.
When using a variable as an argument for a test operator you should almost always enclose it in double-quotes. There are only two situations it is safe to omit the quote marks. The first is when the argument is a literal string with no whitespace or other characters special to the shell (e.g., semicolon). For example, test -b /my/file. The second is using a variable that expands to exactly one element including if that element is the empty string (e.g., set x ''). If the variable is not set, set but with no value, or set to more than one value you must enclose it in double-quotes. For example, test "$x" = "$y". Since it is always safe to enclose variables in double-quotes when used as test arguments that is the recommended practice.
Operators for files and directories¶
-b FILEreturns true ifFILEis a block device.-c FILEreturns true ifFILEis a character device.-d FILEreturns true ifFILEis a directory.-e FILEreturns true ifFILEexists.-f FILEreturns true ifFILEis a regular file.-g FILEreturns true ifFILEhas the set-group-ID bit set.-G FILEreturns true ifFILEexists and has the same group ID as the current user.-k FILEreturns true ifFILEhas the sticky bit set. If the OS does not support the concept it returns false. See https://en.wikipedia.org/wiki/Sticky_bit.-L FILEreturns true ifFILEis a symbolic link.-O FILEreturns true ifFILEexists and is owned by the current user.-p FILEreturns true ifFILEis a named pipe.-r FILEreturns true ifFILEis marked as readable.-s FILEreturns true if the size ofFILEis greater than zero.-S FILEreturns true ifFILEis a socket.-t FDreturns true if the file descriptorFDis a terminal (TTY).-u FILEreturns true ifFILEhas the set-user-ID bit set.-w FILEreturns true ifFILEis marked as writable; note that this does not check if the filesystem is read-only.-x FILEreturns true ifFILEis marked as executable.
Operators for text strings¶
STRING1 = STRING2returns true if the stringsSTRING1andSTRING2are identical.STRING1 != STRING2returns true if the stringsSTRING1andSTRING2are not identical.-n STRINGreturns true if the length ofSTRINGis non-zero.-z STRINGreturns true if the length ofSTRINGis zero.
Operators to compare and examine numbers¶
NUM1 -eq NUM2returns true ifNUM1andNUM2are numerically equal.NUM1 -ne NUM2returns true ifNUM1andNUM2are not numerically equal.NUM1 -gt NUM2returns true ifNUM1is greater thanNUM2.NUM1 -ge NUM2returns true ifNUM1is greater than or equal toNUM2.NUM1 -lt NUM2returns true ifNUM1is less thanNUM2.NUM1 -le NUM2returns true ifNUM1is less than or equal toNUM2.
Both integers and floating point numbers are supported.
Operators to combine expressions¶
COND1 -a COND2returns true if bothCOND1andCOND2are true.COND1 -o COND2returns true if eitherCOND1orCOND2are true.
Expressions can be inverted using the ! operator:
! EXPRESSIONreturns true ifEXPRESSIONis false, and false ifEXPRESSIONis true.
Expressions can be grouped using parentheses.
( EXPRESSION )returns the value ofEXPRESSION.
Note that parentheses will usually require escaping with
\(to avoid being interpreted as a command substitution.
Examples¶
If the /tmp directory exists, copy the /etc/motd file to it:
if test -d /tmp
cp /etc/motd /tmp/motd
end
If the variable MANPATH is defined and not empty, print the contents. (If MANPATH is not defined, then it will expand to zero arguments, unless quoted.)
if test -n "$MANPATH"
echo $MANPATH
end
Parentheses and the -o and -a operators can be combined to produce more complicated expressions. In this example, success is printed if there is a /foo or /bar file as well as a /baz or /bat file.
if test \( -f /foo -o -f /bar \) -a \( -f /baz -o -f /bat \)
echo Success.
end.
Numerical comparisons will simply fail if one of the operands is not a number:
if test 42 -eq "The answer to life, the universe and everything"
echo So long and thanks for all the fish # will not be executed
end
A common comparison is with $status:
if test $status -eq 0
echo "Previous command succeeded"
end
The previous test can likewise be inverted:
if test ! $status -eq 0
echo "Previous command failed"
end
which is logically equivalent to the following:
if test $status -ne 0
echo "Previous command failed"
end
Standards¶
test implements a subset of the IEEE Std 1003.1-2008 (POSIX.1) standard. The following exceptions apply:
The
<and>operators for comparing strings are not implemented.Because this test is a shell builtin and not a standalone utility, using the -c flag on a special file descriptors like standard input and output may not return the same result when invoked from within a pipe as one would expect when invoking the
testutility in another shell.
In cases such as this, one can use
commandtestto explicitly use the system's standalonetestrather than thisbuiltintest.
