01-03-2012
Lookup bash parameter expansion. Here is a url:
BashFAQ/083 - Greg's Wiki
Quote:
# Bourne test "${var+defined}"
This expansion results in nothing if var is undefined. Therefore test returns false. If var is defined (to either "" or something longer), the expansion returns "defined", and therefore test returns true. You could use any non-empty string in place of "defined", but readability is always nice.
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LEARN ABOUT FREEBSD
atf-sh
ATF-SH(1) BSD General Commands Manual ATF-SH(1)
NAME
atf-sh [-s shell] -- interpreter for shell-based test programs
SYNOPSIS
atf-sh script
DESCRIPTION
atf-sh is an interpreter that runs the test program given in script after loading the atf-sh(3) library.
atf-sh is not a real interpreter though: it is just a wrapper around the system-wide shell defined by ATF_SHELL. atf-sh executes the inter-
preter, loads the atf-sh(3) library and then runs the script. You must consider atf-sh to be a POSIX shell by default and thus should not
use any non-standard extensions.
The following options are available:
-s shell Specifies the shell to use instead of the value provided by ATF_SHELL.
ENVIRONMENT
ATF_LIBEXECDIR Overrides the builtin directory where atf-sh is located. Should not be overridden other than for testing purposes.
ATF_PKGDATADIR Overrides the builtin directory where libatf-sh.subr is located. Should not be overridden other than for testing purposes.
ATF_SHELL Path to the system shell to be used in the generated scripts. Scripts must not rely on this variable being set to select a
specific interpreter.
EXAMPLES
Scripts using atf-sh(3) should start with:
#! /usr/bin/env atf-sh
Alternatively, if you want to explicitly choose a shell interpreter, you cannot rely on env(1) to find atf-sh. Instead, you have to hardcode
the path to atf-sh in the script and then use the -s option afterwards as a single parameter:
#! /path/to/bin/atf-sh -s/bin/bash
ENVIRONMENT
ATF_SHELL Path to the system shell to be used in the generated scripts.
SEE ALSO
atf-sh(3)
BSD
September 27, 2014 BSD