CODEWITHSUNDEEP
linuxshellsh
EternaLCompleX
EternaLCompleX

Reputation: 71

Force sh shell to use external function instead of built-in

For some reasons, I want my program to use external functions instead of built-in shell functions (e.g. echo). The program has a call to system() which use /bin/sh to execute the argument.

With bash shell I already know that enable -n <fnc> can prevent the shell to use the built-in function. However, I couldn't find a similar way for sh shell.

Is it possible to do this for sh?

Upvotes: 3

Views: 476

Answers (2)

Fernando Costa Bertoldi
Fernando Costa Bertoldi

Reputation: 860

It was answered in a related question:

Prepend the command with env.

$ env echo "Hello"

env is a standalone program, which doesn't have access to the shell builtins, such as echo, so it will search for echo in the command path.

Upvotes: 1

that other guy
that other guy

Reputation: 123460

To force any shell to use an external executable instead of a builtin command, simply specify it by path:

# Use whatever the shell defaults to
echo "Hello World"

# Always use the specified external binary
/bin/echo "Hello World"

This behavior is specified in POSIX 2.9.1:

If the command name contains at least one slash, the shell shall execute the utility in a separate utility environment with actions equivalent to calling the execl() function

Upvotes: 1

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