Advanced Bash−Scripting Guide

Chapter 33. Scripting With Style
Get into the habit of writing shell scripts in a structured and systematic manner. Even "on−the−fly" and
"written on the back of an envelope" scripts will benefit if you take a few minutes to plan and organize your
thoughts before sitting down and coding.
Herewith are a few stylistic guidelines. This is not intended as an Official Shell Scripting Stylesheet.
33.1. Unofficial Shell Scripting Stylesheet
• Comment your code. This makes it easier for others to understand (and appreciate), and easier for you
to maintain.
PASS="$PASS${MATRIX:$(($RANDOM%${#MATRIX})):1}"
# It made perfect sense when you wrote it last year, but now it's a complete mystery.
# (From Antek Sawicki's "pw.sh" script.)
Add descriptive headers to your scripts and functions.
#!/bin/bash
#************************************************#
# xyz.sh #
# written by Bozo Bozeman #
# July 05, 2001 #
# #
# Clean up project files. #
#************************************************#
BADDIR=65
# No such directory.
projectdir=/home/bozo/projects # Directory to clean up.
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− #
# cleanup_pfiles () #
# Removes all files in designated directory. #
# Parameter: $target_directory #
# Returns: 0 on success, $BADDIR if something went wrong. #
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− #
cleanup_pfiles ()
{
if [ ! −d "$1" ] # Test if target directory exists.
then
echo "$1 is not a directory."
return $BADDIR
fi
}
rm −f "$1"/*
return 0 # Success.
cleanup_pfiles $projectdir
exit 0
Be sure to put the #!/bin/bash at the beginning of the first line of the script, preceding any comment
headers.
• Avoid using "magic numbers", [63] that is, "hard−wired" literal constants. Use meaningful variable
Chapter 33. Scripting With Style 333