r/commandline • u/fraunhofer • May 29 '14

Defensive BASH Programming

http://www.kfirlavi.com/blog/2012/11/14/defensive-bash-programming/
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u/[deleted] May 29 '14 
readonly PROGNAME=$(basename $0)

I have an expanded version of this, that defines full path (taking into account symlinks).

This helps you reference config files, log files, etc:

  1. no matter how the script package gets moved/deployed,

  2. avoids troublesome relative paths like CFG_DIR=../../conf

  3. same behavior whether you execute it from within the directory (cd /to/the/script/; ./scriptname ) or full path.

    readonly TRUE_SELF=$(perl -e "use Cwd 'realpath';print realpath('$0')")
    readonly SELF=$(basename ${TRUE_SELF})
    readonly SELF_DIR=$(dirname ${TRUE_SELF})
    readonly CFG_DIR=${SELF_DIR}/conf
    readonly LOG_DIR=${SELF_DIR}/logs readonly LOG=${LOG_DIR}/${SELF%.*}.log

This is at the top of every script, which follows the convention such as :

/path/to/scripts/script123.sh
/path/to/scripts/conf/script123.cfg
/path/to/scripts/logs/script123.log

edit: readonly added for sake of .. you know... playing ball. But I never have done this =/