Better way to make a bash script self-tracing?

Question

I have certain critical bash scripts that are invoked by code I don't control, and where I can't see their console output. I want a complete trace of what these scripts did for later analysis. To do this I want to make each script self-tracing. Here is what I am currently doing:

#!/bin/bash
# if last arg is not '_worker_', relaunch with stdout and stderr
# redirected to my log file...
if [[ "$BASH_ARGV" != "_worker_" ]]; then
    $0 "$@" _worker_ >>/some_log_file 2>&1  # add tee if console output wanted
    exit $?
fi
# rest of script follows...

Is there a better, cleaner way to do this?

Kevin Reid · Accepted Answer · 2010-03-13 21:27:39Z

13

#!/bin/bash
exec >>log_file 2>&1

echo Hello world
date

exec has a magic behavior regarding redirections: “If command is not specified, any redirections take effect in the current shell, and the return status is 0. If there is a redirection error, the return status is 1.”

Also, regarding your original solution, exec "$0" is better than "$0"; exit $?, because the former doesn't leave an extra shell process around until the subprocess exits.

answered Mar 13, 2010 at 21:27

Kevin Reid

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3 Comments

Kevin Little Over a year ago

Most excellent! I just knew there had to be a more elegant way. Thanks, Kevin; this will go into immediate use...

Aquarius Power Over a year ago

can it also output to current terminal and log to a file? I tried to use tee with exec but found no way..

Aquarius Power Over a year ago

I would like to link to this question where it is possible to see the output and also log it, all commanded from within the script!

Anycorn · Accepted Answer · 2010-03-13 20:48:23Z

2

1 Comment

Kevin Little Over a year ago

@aaa: Yep, I know about "set -x" -- that's one of the things I occasionally make use of in the "# rest of script follows..." section above. I should have mentioned it; thanks for doing so.

acue · Accepted Answer · 2013-09-27 17:04:56Z

0

you may check a common open source trace library with support for bash.

The current available component is for scripting by bash, soon available are Python and C++. Additional going to follow are: Ruby, Java, JavaScript, SQL, PowerShell,...

The license is Apache-2.0

WKR Arno-Can Uestuensoez

answered Sep 27, 2013 at 17:04

acue

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