Question 37586 in Ubuntu Question posted in
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Redirect all bash outputs after the execution is complete – Ubuntu

I have several bash scripts being triggered by crontab at the same times throughout the day. I was looking for a way to log the STDOUT as well as the STDERR to the same file, so that I have something like a Single Source of Truth to see which of the scripts got executed successfully and what was the error in those that didn’t.

OS: Ubuntu 22.04.2 LTS

Currently, each script file is somewhat like this.

    #!/bin/bash

    exec > >(tee -ia ~/path/to/custom/log/file) 2>&1
    set -e # Stop execution if any exception
    echo `date` " " `pwd`

   ... rest of the code ...

I am using tee so that in case we run the script manually, the output/error would be displayed on the screen and we would not have to sort through the log file to find the desired output.

The Problem:
Though the logging is happening, since the programs are triggered at the same time and each program prints certain statements at different points of time, the log file is currently a jumble of all outputs produced by the programs. I was looking for a way to output all the statements of each program collectively after the program is executed entirely so that the log file can be more readable.

I cannot use /var/log/syslog (using the handy-dandy logger command of UNIX) due to ownership issues.

I would be happy to provide additional information if required.

P.S. I understand that exec is changing the file-descriptors. I have also tried subshelling the whole code and using just tee, but to no avail.

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    This is how I managed it. I am aware it is a hacky solution, but it does the job, which is why I am not marking my answer as accepted. I invite better solutions to the issue.

    The rationale is: use a script-specific file descriptor to act as a make-shift buffer for the STDOUT and STDERR. On termination of the program, append the contents to the generic log file for all scripts and clear the script-specific log file.

        #!/bin/bash

    $log_location="/path/to/script/specific/log/file/"
    $station="name-of-code"

    # Define a function to transfer script-specific log to a general log
    handle_logs() {
        cat $log_location/runlog_$station.log >> ~/path/to/custom/log/file
        > $log_location/runlog_$station.log
    }

    # Set up a trap to call the handle_logs function when the script exits
    trap 'handle_logs' EXIT

    exec &> >(tee -ia ~/path/to/custom/log/file)
    set -e # Stop execution if any exception
    echo "$(date) $PWD"
    
    ... rest of the code ...

  2. 0

    What I would do:

    #!/bin/bash

exec &> >(tee -ia ~/path/to/custom/log/file.$$)
set -e # Stop execution if any exception
echo "$(date) $PWD"

    Then when you want to retrieve these logs:

    cat ~/path/to/custom/log/file.* | less
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