Shell Programming and Scripting

I apoligize. As I said I am very new to this. I didn't know it was different for different shells, but I will be sure to include that information next time.
I wanted to let you all know that I got it to work with the following code:

Code:

while (0 == 0)
   ls | grep $name >& /dev/null
   if ($status == 0) then
      break
   else
      sleep 1
   endif
end

A buddy of mine told me that there problems may arise with just saying:

Code:

while (0 == 0)

and that something like:

Code:

x=0
while ($x == 0)

would be better. Can anyone explain why?

You can test many ways in sh, ksh, bash using different delimiters: [] () (()) [[]]
Using builtins is much cheaper than fork/exec a command or two, and the test bits are now built in, so to find a file, it is far simpler to [ -f file ] than ( ls | grep file ), which is two fork/exec and a pipe. For the former, the shell just does an access() call.

Polling files is a sad way to flow control jobs. It harkens back to the days of tape. The shell has better ways to keep track of children, e.g., (proc1&proc2&proc3&wait;proc4), and many times pipes make flow control and intermediate flat files unnecessary while reducing latency by pipeline parallelism: proc4 <(proc1) <(proc2) <(proc3)

Thank you for the information. You are very helpful. I will give this a try. Someone told me about waitpid and so I gave that a try, but I found out that the process is not a child process. I didn't know this before or I would've provided that info. Do you have a suggestion for a book I can buy or a web reference to learn a lot of this stuff? I feel I ask to many questions on here, and you have been very helpful, but I feel I'm in over my head. I'm a chemist by training so this is all new to me. So if you know of a good resource let me know.

Well, usually you can arrange to be parent to things you want to monitor. Basic sh, ksh, bash have wait, which wait for all unless you provide one or more pid. Man Page for wait (all Section 1) - The UNIX and Linux Forums Wait will set $? according to the exit of the waited child, so I like to make a pid list and use a for loop to wait for and report on each. After all, if you are waiting for all N, it does not matter which you sense first. If you want to get the exit time, you can create a wait on each in the background, and wait on that list.

Code:

date "+%Y-%m-%d %H:%M:%S ${0##*/) ($$) Start apps."
( # subshell only waits for subshell's children
for prog in prog1 prog2 prog3
do
( $prog  ; date '+%Y-%m-%d %H:%M:%S ${0##*/) ($$) Exit $! $prog." )&
done
wait
) >logfile 2>&1   # subshell also collects all stdout, stderr for log