[SOLVED] How to read shell built-in commands?

shivaa · 11-20-2012, 09:15 AM

Hello Friends!
How can I read content of a shell built-in command? Since such commands are not simple text files, but executable C language codes, so how can I know that code.
Thanks in advance!

acid_kewpie · 11-20-2012, 09:20 AM

You'd look at the source code I guess. Is that what you mean? I don't see why a built in command is any different to understanding any other command written in C

shivaa · 11-20-2012, 09:44 AM

Hi Chris,
I just want to check content of any simple shell built-in cmd such as "ls" or "cat".
Can we read or find it's full content in a way like we read a simple text file i.e.

Code:

cat /usr/bin/ls

Although using cat will not give any result because /usr/bin/ls isn't a simple text file. Then how can I read that?

Habitual · 11-20-2012, 09:52 AM

Quote:

Originally Posted by shivaa

...because /usr/bin/ls isn't a simple text file. Then how can I read that?

Neither is it a shell built-in

Code:

strings /usr/bin/ls

acid_kewpie · 11-20-2012, 09:54 AM

Those are NOT built in commands. they're just commands. read the source code.

Can I ask why you want to in the first place??

shivaa · 11-20-2012, 10:25 AM

Alright, how can we read source-code of any command available in Unix such as ls, cat, cd, ps etc.?

Quote:

Can I ask why you want to in the first place??

Chris, what do you mean, sorry I didn't understand you question?

frieza · 11-20-2012, 10:48 AM

first of all if you can list them in the filesystem, they are NOT 'internal' (built in) commands, internal commands would be functions within the code of the shell.
second, they are binary files, not text files.
if you want to find out how the programs do what they do, as mentioned you would have to find the source code.
if you are looking at how to USE the command, then run it's man page

Code:

$ man {command}

shivaa · 11-20-2012, 10:56 AM

I think my question is not clear.
I want to read source code of Unix commands such ls, cat, ps etc.
I am not concerned about their usage i.e. using man <command>.

frieza · 11-20-2012, 11:49 AM

fair enough
I believe those commands are part of the package 'coreutils'
http://ftp.gnu.org/gnu/coreutils/

chrism01 · 11-21-2012, 12:13 AM

Try the suggestions here http://www.thegeekstuff.com/2010/02/...linux-command/

fakie_flip · 11-21-2012, 03:56 AM

Quote:

Originally Posted by shivaa

Hello Friends!
How can I read content of a shell built-in command? Since such commands are not simple text files, but executable C language codes, so how can I know that code.
Thanks in advance!

The latest bash as of right now seems to be 4.2.

http://ftp.gnu.org/gnu/bash/bash-4.2.tar.gz

There is the code.

Many distributions support a feature like this:

Code:

apt-get source bash

This will get the source code and everything else used to create the package in a Debian/Ubuntu/Mint based distro.

So you can go to the homepage of the software and look for a download link to source code or use a command for your distro like the one I gave above.

fakie_flip · 11-21-2012, 04:02 AM

Also, to find out what package a command belongs to:

Debian/Ubuntu:

dpkg -S /bin/ls

Redhat/Fedora:

rpm -qf /bin/ls

I tested this on my machine running CentOS.

[bullshark@alpha ~]$ rpm -qf /bin/ls
coreutils-8.4-19.el6.x86_64
[bullshark@alpha ~]$

Now you know what package that command belongs to, you can use another command provided by your distro to download the source code, or go find it on the homepage from the web.

shivaa · 12-07-2012, 12:05 PM

Thanks everyone!