Use system command instead of Bash builtin without specifying the full path

Question

I use Bash as my interactive shell and I was wondering if there was an easy way to get Bash to run a system command instead of a shell builtin command in the case where they both share the same name.

For example, use the system kill (from util-linux) to print the process id (pid) of the named process(es) instead of sending a signal:

$ /bin/kill -p httpd
2617
...

Without specifying the full path of the system command, the Bash builtin is used instead of the system command. The kill builtin doesn’t have the -p option so the command fails:

$ kill -p httpd
bash: kill: p: invalid signal specification

I tried the answers listed in Make bash use external `time` command rather than shell built-in but most of them only work because time is actually a shell keyword – not a shell builtin.

Other than temporarily disabling the Bash builtin with enable -n kill, the best solution I’ve seen so far is to use:

$(which kill) -p httpd

Are there other easier (involve less typing) ways to execute an external command instead of a shell builtin?

Note that kill is just an example and I’d like a generalised solution similar to the way that prefixing with the command builtin prevents functions which have the same name as an external command from being run. In most cases, I usually prefer to use the builtin version as it saves forking a new process and some times the builtin has features that the external command doesn’t.

Answer 1

Assuming env is in your path:

env kill -p http

env runs the executable file named by its first argument in a (possibly) modified environment; as such, it does not know about or work with shell built-in commands.

This produces some shell job control cruft, but doesn't rely on an external command:

exec kill -p bash &

exec requires an executable to replace the current shell, so doesn't use any built-ins. The job is run in the background so that you replace the forked background shell, not your current shell.

Answer 2

The simplest way to do what you want might be to put the line

alias kill="/bin/kill"

into your ~/.bashrc file. After that, each new login/invocation of bash will interpret "kill" as /bin/kill.

Answer 3

If you know a solution that requires some typing and you want a solution that requries less typing, build it:

runFile() { local cmd="$1"; shift; cmd="$(which "$cmd")" && "$cmd" "$@"; }

Abbreviating stuff that normally takes some effort is what computers excel at.

Answer 4

In this very specific case, the command pgrep is an exact match for the need.

In a general sense, a function works. From "file command":

fcmd(){ local a=$1; shift; $(which "$a") "$@"; }

call as

fcmd kill -p httpd

But if you need less typing, there is no shorter way than a good alias.

From the concept "list pid" (lp):

alias lp='/bin/kill -p'

then, just type:

lp httpd

Answer 5

(In zsh) You can prefix any command name with an = sign to get the system version instead of a builtin. This is also a handy way to dodge any aliases that mess up a specific scenario.

$ =kill -p httpd

Answer 6

You could send a bugreport against your kill manpage and ask why this includes non-standard options that are taken from pkill and use pkill whenever you like to get the features from pkill.

If you call:

pkill httpd

you avoid the problems you describe.