Execute a command when another command is executed on linux

Question

I was wondering if there is a command to "listen" to commands on Linux. What I mean, for every time a command is executed, for example sccs edit file, chmod +x file is executed

Answer 1

If this is just for your own use, you can create aliases or shell functions with the same name:

In bash:

alias ls="ls -l"

Then, whenever you do ls , it actually does ls -l (and any extra arguments are added after that).

Aliases are only useful to rename a command, and/or add a few initial parameters; you can't do anything more complicated. You can make the alias run a script, of course, and do anything you like that way.

Alternatively, you can create a shell function (put it in your .bashrc file, for example):

Again, in bash:

function sccs () {
   /usr/bin/sccs "$@"
   status=$?
   chmod +x "$1"
   return $status
}

I've no idea what an sccs command line looks like, so I expect you'd need to do something cleverer in there, but you get the idea, I hope.