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One of the great sins in programming is trying to write code in one language like code from another language. Having said that, I’m a shell scripting newbie. So when I had cause to write some bash, I found myself reaching for some python ‘home comforts’. Okay, so what I actually did wasn’t so bad function log () { echo "log: $@ " > &2 } I think this is a fairly common approach to ‘logging’ in…

One of the great sins in programming is trying to write code in one language like code from another language.

Having said that, I’m a shell scripting newbie. So when I had cause to write some bash, I found myself reaching for some python ‘home comforts’.

Okay, so what I actually did wasn’t so bad

function log() {
    echo "log: $@" >&2
}

I think this is a fairly common approach to ‘logging’ in bash.

But around the same time, I was reading about arrays in bash, and that gave me an idea for how you could implement python-style logging, with variable logging levels.

Code

#!/usr/bin/env bash
_LEVELS=(DEBUG INFO WARNING ERROR CRITICAL)
export DEBUG=10
export INFO=20
export WARNING=30
export ERROR=40
export CRITICAL=50
function log() {
    # Write a message to logging at the given level
    #
    # Usage: log <level> <message>
    local effective=${LOGLEVEL:-$WARNING};
    local level=$1;
    local levelname=${_LEVELS[$((level/10-1))]};
    shift;
    if [[ $level -ge $effective ]]; then
        printf "%s:%s: %s\n" "$levelname" "$0" "$@" >&2;
    fi
}
function setLevel() {
    # Set the logging level
    #
    # Usage: setLevel <level>
    export LOGLEVEL=$1
}
# convenience functions
alias debug='log $DEBUG'
alias info='log $INFO'
alias warning='log $WARNING'
alias warn=warning
alias error='log $ERROR'
alias critical='log $CRITICAL'

Example Usage

If you want to make use of this, just save the script somewhere locally and source it

$ source logging.sh
$ setLevel $INFO
$ log $INFO "hello world"
INFO:bash: hello world
$ log $DEBUG "can't see me"
$ setLevel $DEBUG
$ debug "now you see me"
DEBUG:bash: now you see me

Better yet, throw your bash script in the trash, and re-write it in python :p

Chris.

Python-style Logging in Bash

Code

Example Usage

Comments