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https://github.com/fish-shell/fish-shell
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129 lines
4.6 KiB
Text
129 lines
4.6 KiB
Text
\section test test - perform tests on files and text
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\subsection test-synopsis Synopsis
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\fish{synopsis}
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test [EXPRESSION]
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[ [EXPRESSION] ]
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\endfish
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\subsection test-description Description
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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.
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The first form (`test`) is preferred. For compatibility with other shells, the second form is available: a matching pair of square brackets (`[ [EXPRESSION ] ]`).
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The following operators are available to examine files and directories:
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- `-b FILE` returns true if `FILE` is a block device.
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- `-c FILE` returns true if `FILE` is a character device.
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- `-d FILE` returns true if `FILE` is a directory.
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- `-e FILE` returns true if `FILE` exists.
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- `-f FILE` returns true if `FILE` is a regular file.
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- `-g FILE` returns true if `FILE` has the set-group-ID bit set.
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- `-G FILE` returns true if `FILE` exists and has the same group ID as the current user.
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- `-L FILE` returns true if `FILE` is a symbolic link.
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- `-O FILE` returns true if `FILE` exists and is owned by the current user.
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- `-p FILE` returns true if `FILE` is a named pipe.
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- `-r FILE` returns true if `FILE` is marked as readable.
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- `-s FILE` returns true if the size of `FILE` is greater than zero.
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- `-S FILE` returns true if `FILE` is a socket.
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- `-t FD` returns true if the file descriptor `FD` is a terminal (TTY).
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- `-u FILE` returns true if `FILE` has the set-user-ID bit set.
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- `-w FILE` returns true if `FILE` is marked as writable; note that this does not check if the filesystem is read-only.
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- `-x FILE` returns true if `FILE` is marked as executable.
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The following operators are available to compare and examine text strings:
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- `STRING1 = STRING2` returns true if the strings `STRING1` and `STRING2` are identical.
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- `STRING1 != STRING2` returns true if the strings `STRING1` and `STRING2` are not identical.
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- `-n STRING` returns true if the length of `STRING` is non-zero.
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- `-z STRING` returns true if the length of `STRING` is zero.
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The following operators are available to compare and examine numbers:
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- `NUM1 -eq NUM2` returns true if `NUM1` and `NUM2` are numerically equal.
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- `NUM1 -ne NUM2` returns true if `NUM1` and `NUM2` are not numerically equal.
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- `NUM1 -gt NUM2` returns true if `NUM1` is greater than `NUM2`.
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- `NUM1 -ge NUM2` returns true if `NUM1` is greater than or equal to `NUM2`.
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- `NUM1 -lt NUM2` returns true if `NUM1` is less than `NUM2`.
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- `NUM1 -le NUM2` returns true if `NUM1` is less than or equal to `NUM2`.
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Note that only integers are supported. For more complex mathematical operations, including fractions, the `env` program may be useful. Consult the documentation for your operating system.
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Expressions can be combined using the following operators:
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- `COND1 -a COND2` returns true if both `COND1` and `COND2` are true.
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- `COND1 -o COND2` returns true if either `COND1` or `COND2` are true.
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Expressions can be inverted using the `!` operator:
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- `! EXPRESSION` returns true if `EXPRESSION` is false, and false if `EXPRESSION` is true.
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Expressions can be grouped using parentheses.
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- `( EXPRESSION )` returns the value of `EXPRESSION`.
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Note that parentheses will usually require escaping with `\(` to avoid being interpreted as a command substitution.
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\subsection test-example Examples
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If the `/tmp` directory exists, copy the `/etc/motd` file to it:
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\fish
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if test -d /tmp
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cp /etc/motd /tmp/motd
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end
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\endfish
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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.)
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\fish
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if test -n "$MANPATH"
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echo $MANPATH
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end
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\endfish
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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.
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\fish
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if test \( -f /foo -o -f /bar \) -a \( -f /baz -o -f /bat \)
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echo Success.
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end.
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\endfish
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\subsection test-standards Standards
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`test` implements a subset of the <a href="http://www.unix.com/man-page/POSIX/1/test/">IEEE Std 1003.1-2008 (POSIX.1) standard</a>. The following exceptions apply:
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- The `<` and `>` operators for comparing strings are not implemented.
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- 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.
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In cases such as this, one can use `command` `test` to explicitly use the system's standalone `test` rather than this `builtin` `test`.
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