оценить выражение (evaluate expression)
Описание (Description)
The test utility shall evaluate the expression and indicate the
result of the evaluation by its exit status. An exit status of
zero indicates that the expression evaluated as true and an exit
status of 1 indicates that the expression evaluated as false.
In the second form of the utility, where the utility name used is
[ rather than test, the application shall ensure that the closing
square bracket is a separate argument. The test and [ utilities
may be implemented as a single linked utility which examines the
basename of the zeroth command line argument to determine whether
to behave as the test or [ variant. Applications using the exec()
family of functions to execute these utilities shall ensure that
the argument passed in arg0 or argv[0] is '[' when executing the
[ utility and has a basename of "test" when executing the test
utility.
