Re-coding basic shell commands in C

daviest11 · 04-09-2002, 09:39 AM

Hi All,

I'm trying to write my own shell for linux - a small part of a major assignment. Using C I've got to write simple versions of the following shell commands:
ls [-al]
pwd
cd
ps [-A]
and kill

Could anybody help? If not, does anybody know any sites that might have simple versions of these functions. It'd save my life!

crabboy · 04-09-2002, 11:10 AM

Sounds like a good assignment.

None of those commands should be that difficult to write. I have written some of these commands in part on this site, if you spend some time searching you may find them.

I'd suggest spending you time looking through a good book: "Advanced Programming in the UNIX Environment" by Stevens. It's an excellent book and will have examples of how to do most of those commands.

daviest11 · 04-11-2002, 10:25 AM

Cheers for that.
I've not got much time to get this done and I'm fairly new to all this OS stuff. I've written a changedir script - how do I apply it to the current shell rather than the one in which it is executed (i think that makes sense)??
I'm also well stuck on what system calls would be approriate for the ps command,

Thanks again.
Tom

crabboy · 04-11-2002, 11:50 AM

For ps take a look at the source code for top. It looks like they read from the /proc filesystem. There is a directory for each pid in /proc. In the pid directories there is a stats file. These are the process stats.