SC2002

Useless cat. Consider 'cmd < file | ..' or 'cmd file | ..' instead.

Problematic code:

cat file | tr ' ' _ | grep a_
cat file | ( while read i; do echo "${i%?}"; done )

Correct code:

< file tr ' ' _ | grep a_  # **simple commands only, won't work with compounds
( while read i; do echo "${i%?}"; done ) < file # postfix works for everything

Rationale:

cat is a tool for con"cat"enating files. Reading a single file as input to a program is considered a Useless Use Of Cat (UUOC).

It's more efficient and less roundabout to simply use redirection. This is especially true for programs that can benefit from seekable input, like tail or tar.

Many tools also accept optional filenames, e.g. grep -q foo file instead of cat file | grep -q foo.

Exceptions

None.