How does VARIABLE=() { function definition } work in bash
WARNING – this question is about the Bash before the shellshock vulnerability, due to which it was changed.
I have seen something like this in my bash ENV:
module=() { eval `/usr/bin/modulecmd bash $*` }
How does this construct work? What is it called?
I’m not asking about modulecmd, I am asking about the entire construct.
It’s really a function named module. It appears in environment variables when you export a function.
$ test() { echo test; }
$ export -f test
$ env | sed -n '/test/{N;p}'
test=() { echo test
}
From bash documentation – export:
export
export [-fn] [-p] [name[=value]]Mark each name to be passed to child processes in the environment. If
the -f option is supplied, the names refer to shell functions;
otherwise the names refer to shell variables. The -n option means to
no longer mark each name for export. If no names are supplied, or if
the -p option is given, a list of exported names is displayed. The -p
option displays output in a form that may be reused as input. If a
variable name is followed by =value, the value of the variable is set
to value.The return status is zero unless an invalid option is supplied, one of
the names is not a valid shell variable name, or -f is supplied with a
name that is not a shell function.