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Redirecting standard output to a file containing the pid of the logging process

Answer 1

A:

You cannot know the PID of a process before you created it.

Therefore this is not possible, you should rewrite the program that is called, to use getpid() to forge a log name from its own PID.

Benoit 2010-10-04 12:21:06

Answer 2

+2 A:

You can wrap your program execution into bash script. The bash process will be replaced with your program on exec call. So:

#!/bin/bash
exec my_program > $$.log

dma_k 2010-10-04 12:56:55

This solved my problem! Thanks! Actually, I tried something similar, only instead of running a script as a separate bash job so that exec could replace that instance of bash with my_program, I tried the same concept but using the -c command line option for bash, but it didn't work.

ticklemynausea 2010-10-04 14:08:37

bash -c "exec echo $$" outputs 3357. // on the same shell, echo $$ outputs 3357

ticklemynausea 2010-10-04 14:11:13

@ticklemynausea: You need think about when `$$` is actually substituted by bash with the value. If you write (and most of us do it this way) `bash -c "exec sleep 300 > $$.log"`, the `$$` is not replaced by the bash we are about to run, but with parent (e.g. current) bash! Now feel the difference: `bash -c 'exec sleep 300 > $$.log'`

dma_k 2010-10-05 09:22:14

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