What is /bin/sh -c?

Question

What does /bin/sh -c mean? What does -c do?

Shorthorn

Answer 1

From the man-page of bash:

-c string

If the -c option is present, then commands are read from string. If there are arguments after the string, they are assigned to the positional parameters, starting with $0.

Example:

$ bash -c ls

will launch bash and execute the command ls.

/bin/sh is usually a symlink to a shell.

Sealey

How is that different to without -c ? – Algophobia

You can pass a script as argument, bash myScript but it will open myScript and interpret the commands. This is not the same as bash -c someCommand. Compare what happens if you do bash ls and bash -c ls for instance. – Sealey

/bin/sh -c grep "cpu cores" /proc/cpuinfo | uniq | sed -e 's/[^0-9] The above command does not give desired result. Why is it so? Whereas /bin/sh -c ls | grep c works fine. I am not getting this odd behavior. It would be great if you can explain it too. – Shirleenshirlene

I got it. It needs to be formatted string. /bin/sh -c 'grep "$0" /proc/cpuinfo | uniq | sed -e "$1"' "cpu cores" 's/[^0-9]*//g' worked like a charm. – Shirleenshirlene

You have two options: bash script.sh or bash -c 'ls -la'. -c parameter is the command with its parameters, that will be passed to the bash command interpreter. If your standard command interpreter is bash, then ls -la and bash -c 'ls -la' are equivalent – Shane

Answer 2

With -c (command) it returns to the first shell instead of let open a new one.
It is very similar to: sudo su -l -c 'echo "run a command and return"'
Example:

#sudo su -l knoppix -c 'echo "run a command as ${USER} and return"'
run a command as knoppix and return
#

Horary

Well, you do not have to give password with /bin/sh. – Wynn

the sequence to execute in simple quotes, thank you! – Nucleotidase

Answer 3

Let's break it down.

/bin/sh: This launches a Bourne shell, a basic command-line interpreter that is available on most Unix-like operating systems.

-c: This option tells the shell to read the command from the following string. It allows you to specify a command inline, without the need to write a separate script file. This option works in both sh and bash.

For example, if you run:

/bin/sh -c "echo Hello, World!"

This command tells sh to execute the echo Hello, World! string.

Yardstick