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.

The command echo "$(false)" will return true, whereas false of course returns false – beware of the ignored exit code before blindly altering scripts. If using set -e, the correct substitution of echo "$(cmd)" would be cmd || true.

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.