Correct way to use Linux commands in bash script

Question

What is the best and most correct way to use Linux commands in bash scripts in terms of path to it? Is that correct to use only ip addr show, relying on shell path, or should I find a path to the command first (like with whereis ip or command -v ip), assign the output to some variable and then use that?

Answer 1

Personally, I just rely on the PATH and invoke "bare" commands.

If you don't trust the user's PATH, you can reset it to a minimal default:

PATH=$(/usr/bin/getconf PATH)

grep "$pattern" "$file"

Answer 2

I tend to set the path to utilities at the top of my path, avoiding any dependency on PATH. One potential attack is to set the PATH before running a bash script. Setting the path for each utility is painful, but it can protect against that sort of attack.

In cases where you are authoring for multiple environments in which the utilities are found in different places, e.g. Debian and MacOS, I check for the path, e.g.

[ -f /usr/bin/grep ] && GREP=/usr/bin/grep || GREP=/bin/grep