Unix Programming - Taxonomy of Unix IPC Methods - Wrappers
Wrappers
The opposite of a shellout is a wrapper. A
wrapper creates a new interface for a called program, or specializes
it. Often, wrappers are used to hide the details of elaborate shell
pipelines. We'll
discuss interface wrappers in Chapter11. Most specialization wrappers are quite
simple, but nevertheless very useful.
As with shellouts, there is no associated protocol because the
programs do not communicate during the execution of the callee; but
the wrapper usually exists to specify arguments that modify the
callee's behavior.
Case Study: Backup Scripts
Specialization wrappers are a classic use of the Unix shell and
other scripting languages. One kind of specialization wrapper
that is both common and representative is a backup script. It may be a
one-liner as simple as this:
tar -czvf /dev/st0 "$@"
This is a wrapper for the
tar(1)
tape archiver utility which simply supplies one fixed argument (the
tape device /dev/st0) and passes to tar all the other arguments
supplied by the user (“$@”).[71]
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