\section test test - perform tests on files and text \subsection test-synopsis Synopsis \fish{synopsis} test [EXPRESSION] [ [EXPRESSION] ] \endfish \subsection test-description 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. \subsection test-files Operators for files and directories - `-b FILE` returns true if `FILE` is a block device. - `-c FILE` returns true if `FILE` is a character device. - `-d FILE` returns true if `FILE` is a directory. - `-e FILE` returns true if `FILE` exists. - `-f FILE` returns true if `FILE` is a regular file. - `-g FILE` returns true if `FILE` has the set-group-ID bit set. - `-G FILE` returns true if `FILE` exists and has the same group ID as the current user. - `-k FILE` returns true if `FILE` has the sticky bit set. If the OS does not support the concept it returns false. See https://en.wikipedia.org/wiki/Sticky_bit. - `-L FILE` returns true if `FILE` is a symbolic link. - `-O FILE` returns true if `FILE` exists and is owned by the current user. - `-p FILE` returns true if `FILE` is a named pipe. - `-r FILE` returns true if `FILE` is marked as readable. - `-s FILE` returns true if the size of `FILE` is greater than zero. - `-S FILE` returns true if `FILE` is a socket. - `-t FD` returns true if the file descriptor `FD` is a terminal (TTY). - `-u FILE` returns true if `FILE` has the set-user-ID bit set. - `-w FILE` returns true if `FILE` is marked as writable; note that this does not check if the filesystem is read-only. - `-x FILE` returns true if `FILE` is marked as executable. \subsection test-strings Operators for text strings - `STRING1 = STRING2` returns true if the strings `STRING1` and `STRING2` are identical. - `STRING1 != STRING2` returns true if the strings `STRING1` and `STRING2` are not identical. - `-n STRING` returns true if the length of `STRING` is non-zero. - `-z STRING` returns true if the length of `STRING` is zero. \subsection test-numbers Operators to compare and examine numbers - `NUM1 -eq NUM2` returns true if `NUM1` and `NUM2` are numerically equal. - `NUM1 -ne NUM2` returns true if `NUM1` and `NUM2` are not numerically equal. - `NUM1 -gt NUM2` returns true if `NUM1` is greater than `NUM2`. - `NUM1 -ge NUM2` returns true if `NUM1` is greater than or equal to `NUM2`. - `NUM1 -lt NUM2` returns true if `NUM1` is less than `NUM2`. - `NUM1 -le NUM2` returns true if `NUM1` is less than or equal to `NUM2`. Both integers and floating point numbers are supported. \subsection test-combinators Operators to combine expressions - `COND1 -a COND2` returns true if both `COND1` and `COND2` are true. - `COND1 -o COND2` returns true if either `COND1` or `COND2` are true. Expressions can be inverted using the `!` operator: - `! EXPRESSION` returns true if `EXPRESSION` is false, and false if `EXPRESSION` is true. Expressions can be grouped using parentheses. - `( EXPRESSION )` returns the value of `EXPRESSION`. Note that parentheses will usually require escaping with `\(` to avoid being interpreted as a command substitution. \subsection test-example Examples If the `/tmp` directory exists, copy the `/etc/motd` file to it: \fish if test -d /tmp cp /etc/motd /tmp/motd end \endfish 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.) \fish if test -n "$MANPATH" echo $MANPATH end \endfish 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. \fish if test \( -f /foo -o -f /bar \) -a \( -f /baz -o -f /bat \) echo Success. end. \endfish Numerical comparisons will simply fail if one of the operands is not a number: \fish 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 \endfish A common comparison is with $status: \fish if test $status -eq 0 echo "Previous command succeeded" end \endfish The previous test can likewise be inverted: \fish if test ! $status -eq 0 echo "Previous command failed" end \endfish which is logically equivalent to the following: \fish if test $status -ne 0 echo "Previous command failed" end \endfish \subsection test-standards 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 `test` utility in another shell. In cases such as this, one can use `command` `test` to explicitly use the system's standalone `test` rather than this `builtin` `test`.