SC2005

Useless echo? Instead of echo $(cmd), just use cmd

Problematic code:

echo "$(cat 1.txt)"
echo `< /dev/urandom tr -dc _A-Z-a-z-0-9 | head -c6`

Correct code:

cat 1.txt # In bash, but faster and still sticks exactly one newline: printf '%s\n' "$(<1.txt)"
# The original `echo` sticks a newline; we want it too.
< /dev/urandom tr -dc _A-Z-a-z-0-9 | head -c6; echo

Rationale

The command substitution $(foo) yields the result of command foo with trailing newlines erased, and when it is passed to echo it generally just gives the same result as foo.

Exceptions

One may want to use command substitutions plus echo to make sure there is exactly one trailing newline. The special command substitution $(<file) in bash is also un-outline-able.

Anyway, echo is still not that reliable (see SC2039#echo-flags) and printf should be used instead.