(coreutils.info)test invocation

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Enter node , (file) or (file)node

16.3 `test': Check file types and compare values
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`test' returns a status of 0 (true) or 1 (false) depending on the
evaluation of the conditional expression EXPR.  Each part of the
expression must be a separate argument.

   `test' has file status checks, string operators, and numeric
comparison operators.

   `test' has an alternate form that uses opening and closing square
brackets instead a leading `test'.  For example, instead of `test -d
/', you can write `[ -d / ]'.  The square brackets must be separate
arguments; for example, `[-d /]' does not have the desired effect.
Since `test EXPR' and `[ EXPR ]' have the same meaning, only the former
form is discussed below.

   Synopses:

     test EXPRESSION
     test
     [ EXPRESSION ]
     [ ]
     [ OPTION

   Due to shell aliases and built-in `test' command, using an unadorned
`test' interactively or in a script may get you different functionality
than that described here.  Invoke it via `env' (i.e., `env test ...')
to avoid interference from the shell.

   If EXPRESSION is omitted, `test' returns false.  If EXPRESSION is a
single argument, `test' returns false if the argument is null and true
otherwise.  The argument can be any string, including strings like
`-d', `-1', `--', `--help', and `--version' that most other programs
would treat as options.  To get help and version information, invoke
the commands `[ --help' and `[ --version', without the usual closing
brackets.  Note: Common options.

   Exit status:

     0 if the expression is true,
     1 if the expression is false,
     2 if an error occurred.

File type tests

-[bcdfhLpSt]

Access permission tests

-[gkruwxOG]

File characteristic tests

-e -s -nt -ot -ef

String tests

-z -n = !=

Numeric tests

-eq -ne -lt -le -gt -ge

Connectives for test

! -a -o