Shell Programming and Scripting

All,

I have to have my script wait for another script when it is being executed. I used

Code:

fuser -f scriptname

to get the PID of the script but when passed the PID to wait command, the command does not accept it as a PID.

Below is the example:

my.script1:

Code:

fuser_result=`fuser -f my.script2`
echo " PID using my.file is : $fuser_result"
wait $fuser_result
echo " Script2 Complete. Now continue processing"

Before I ran the script, I made sure my.script2 is open and being executed
my.script1 does not wait for my.script2 at all. The last echo statement runs immediately after the wait statement.

Also the echo PID statement gives me outputs like below:

I run:

Code:

 PID using my.file is : 3436698

II run:

Code:

 PID using my.file is : 3436698 942486

III run:

Code:

 PID using my.file is : 19734589

From this its clear that the wait command did not see the PIDs from fuser command as PIDs. Is there any way to format the same so that I can make my wait command work?

Also as shown in II run sometimes, I get more than 1 PID from fuser. Let me know how to handle those kind of situations too!

Let me know for any questions.

Thanks
Bharath

You can wait your child process.

How do I get the Child Processes from the fuser output. I have to read the output and store the same into a variable which I can wait on. How do I do that?

You can only use the "wait" command for a process which your current shell set off into background.
See "man wait" (even though "wait" is usually a shell builtin).

Code:

#!/bin/ksh
# background script2 and wait
nohup script2 & ; MYPID=$!
wait ${MYPID} ; echo "Finished: ${MYPID}"

Hi, bharath.gct,

The actual problem is, as you may have already guessed, not
to discover the pids, whether they are children or not (by the way,
with a single exception, every process is a child to another one.)

The actual problem is that YOU CAN'T wait (thru the "wait" command
in shell, or the wait(2) system call in a binary program) for a process
which was not launched by you (your shell or your program).

Wait can only be used with children processes that you directly
spawned (actually, fork(2)'d) - like when your shell launches a
command to the background, via "&".

So, if the process you want to wait for is not of your own, direct,
"breed", sorry, you'll have to figure out some other way to do it.
"Wait" wasn't designed for that, only for actual children, and not for
siblings, cousins, nephews, grandsons, mothers-in-law (or total
strangers) kind of processes.

One way could be, once you discover the pid, keep checking, say, every
1 or 5 seconds, ps output until the process disappears... not very efficient,
but effective.

Hope this helps.

Mario.