I spent the weekend writing scripts to handle various situations where a very long command line was necessary. Usually it was handling one command that had to be repeated for each file in a directory.
For example, pkg_add on FreeBSD doesn't handle more than 200 packages at a time on the command line. So I spent the first part of the evening writing little scripts like:
# sh for pkg in * do pkg_add $pkg done
Those scripts work, but later I found a utility designed just for this particular difficulty: xargs.
According to the man page:
The xargs utility reads space, tab, newline and end-of-file delimited arguments
from the standard input and executes the specified utility with them as
arguments.
Basically it means you pipe a list of "arguments" to xargs. Xargs sucks up the list and then feeds them back one (or more) at a time to the specified program until they are all gone. For my application, this worked like a charm. My already small script was reduced to:
ls | xargs -n1 pkg_add
