SC2230 – ShellCheck Wiki

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which is non-standard. Use builtin command -v instead.

Optional - deprecate-which

This is an optional rule, which means that it has a special "long name" and is not enabled by default. See the optional page for more details. In short, you have to enable it with the long name instead of the "SC" code like you would with a normal rule:

.shellcheckrc

enable=deprecate-which # SC2230

Problematic code:

which grep

Correct code:

# For the path of a single, unaliased, external command,
# or to check whether this will just "run" in this shell:
command -v grep
# To check whether commands exist, without obtaining a reusable path:
hash grep

Rationale:

which is a non-standard, external tool that locates an executable in PATH. command -v is a POSIX standard builtin, which uses the same lookup mechanism that the shell itself would.

Exceptions:

This check is opt-in only in 0.7.1+, and you may choose to ignore it in earlier versions. which is very common, and some prefer its executable-or-nothing behavior over command -v's handling of builtins, functions and aliases.

Caveats:

command -v does not check ALL parameters

command -v succeeds (with exit code 0) if any command exists:

# grep is in /usr/bin/grep
# foobar is not in path
#
$ command -v -- grep foobar; echo $?
0

In the above example, it should have failed and exited with 1 unless all commands exist, if it were to be a replacement for which. Other problems associated with command include its inclusion of builtins, aliases, and functions.

An alternative is:

$ hash <file1> <file2>

Which observes the standard behaviour of failures.

To obtain a path, type -p can be used instead. Like command -v, it has a similarly quirky behavior with builtins, aliases, and functions, although this is arguably milder since it would print nothing for these cases. The failure condition is similar to hash.

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