3

I have a very short process for which i want to check the environmental variables for debugging purposes. The process is instant from a human perspective. The example illustrates it better.

Example

user:~$ ps aux | grep grep
user   2349  0.0  0.0   4384   840 pts/1    S+   14:47   0:00 grep --color=auto grep

The pid of the process was 2349. If I check the environmental variables (or other info):

#Pretty print of environmental variables#
user:~$ xargs --null --max-args=1 echo < /proc/2349/environ
bash: /proc/2349/environ: No such file or directory

The info has vanished with the process.

What to do before running the process to be able to list the variables once the precess is finished?

7

if you have strace

strace -v -e execve cmd

If the values of the variables are too long you can increase the string size with -s

strace -v -s 10000 -e execve cmd
5

I would move the binary to one side and create a wrapper that dumps the environment to a file and then calls the original.

E.g.

mv ${cmd} ${cmd}.moved

Then create a new file ${cmd}:

#!/bin/sh
env > /tmp/cmd-env.log
exec ${cmd}.moved "$@"

And, don't forget the permissions:

chmod a+rx ${cmd}

Then, wait for it to run again, and read the environment from /tmp/cmd-env.log.

Finally, put the original program back where it came from:

mv ${cmd}.moved ${cmd}

Of course, it may be possible to avoid moving the binary by putting the wrapper in another bin directory earlier in $PATH.

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