[SOLVED] BASH: get PID of first command in pipe

[xyz000]

Hi,

I understand that $! is the PID of a command. For example:

#!/bin/bash
myprogram &
echo "PID of myprogram is $!"

I'd like to send the output of "myprogram" to both console and to a log file using the "tee" command but I also want to store the PID of "myprogam". Something like this:

#!/bin/bash
myprogram | tee ./logfile &
echo "PID of myprogram is $!"

The problem is that $! is now the PID of "tee" rather than the PID of "myprogram". Any suggestions how to achieve what I need? Thanks.

[lemons]

I think you could just write something like this:

#!/bin/bash
myprogram > logfile
MYPROGRAM_PID=$!
echo "PID = $MYPROGRAM_PID" >> logfile
echo "PID of myprogram is $MYPROGRAM_PID"

so the PID is saved at the end of the file. I guess this wouldn't work if it's an ongoing program.

If it is a C program, you could include the header <unistd.h> and use the method getpid() and print that out first, so it is the first thing written to the log file.

[Cabhan]

Unfortunately, you can't really do this easily. One suggestion I saw was using named pipes:

#!/bin/bash

fifoname=/tmp/myfifo.$$
mkfifo "$fifoname"

myprogram > "$fifoname" &
echo "PID is $!"

tee ./logfile < "$fifoname"

This way, we don't need to directly pipe myprogram into tee, so we can insert code in the middle.

[xyz000]

Fixed. Thanks for the suggestions. The named pipe works well. Repeated here with a few small modifications:

#!/bin/bash
FIFONAME=/tmp/myfifo.$$
rm -f $FIFONAME
mkfifo $FIFONAME
myprogram > $FIFONAME &
MYPROGRAM_PID=$!
cat $FIFONAME | tee ./logfile