The `backtick` program

backtick runs a program and stores its output in an environment variable, then executes another program.

Interface

In an execlineb script:

     backtick [ -i | -D default ] [ -n ] variable { prog1... } prog2...

backtick reads prog1... in a block and unquotes it.
It runs prog1... as a child process and saves its output in memory. This output must not contain a null character.
backtick execs into the modified prog2..., with variable added to the environment with prog1...'s output as a value.

-i : insist. If prog1 crashes or exits non-zero, backtick exits with an approximation of the same exit code.
-D default : default value. If prog1 crashes or exits non-zero, default is used as variable's value. If neither the -i nor the -D option have been given, backtick execs into prog2... no matter what prog1 does, with the null word as variable's value if prog1 didn't write anything before dying.
-n : chomp an ending newline off prog1...'s output.

You can start prog2... with "import -u variable" to perform variable substitution.