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BASH CODING STYLE
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Contents:
1. Introduction
2. Naming Convention
3. Comments
4. Coding Styles
5. Basic formating
6. If, For, and While
7. Use of shell builtin commands
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1. Introduction
The main reason for using a consistent set of coding conventions is to
improve the readability of the source code, allowing core team to
understand new code more quickly and thoroughly.
2. Naming Convention
The names of files, variables and functions serve as comments of a sort.
So don’t choose terse names—instead, look for names that give useful
information about the meaning. Names should be English, like other
comments. They should be descriptive and correspond or to be appropriate to
functionality which it implements. Names should not be longer than 30
characters. Instead spaces use underscores to separate words in a name. And
it is always good idea to stick to lower case, exceptions are only global
or enviroment variables.
iCantReadThis.Shell # Bad naming
backup_mysql_databases.sh # Good naming
PATH='/bin:/home/user/bin' # Global variable (capitals)
max_users=0 # Local variable
print_user_password() { #
echo $password # Function naming example
} #
3. Comments
The total length of a line (including comment) must not exceed more than 80
characters. Every file must be documented with an introductory comment that
provides shorthand information on the file name and its contents.
#!/bin/bash
# info: adding web domain
Consecutive line end comments start in the same column. A blank will always
follow the introductory character of the comment to simplify the detection
of the beginning of the word.
cp foo bar # Copy foo to bar
rm -f foo # Remove foo
Use an extra '#' above and below the comment in the case of multi-line
comments:
#
# Modify the permissions on bar. We need to set them
# to root/sys in order to match the package prototype.
#
chown root bar
chgrp sys bar
Each script have 4 logical part Variables, Verifications, Action and Vesta.
Such parts should be devided by following frames.
#----------------------------------------------------------#
# Variable&Function #
#----------------------------------------------------------#
5. Basic Formating
The indentation of program constructions has to agree with the logic
nesting depth. The indentation of one step usually is 4 spaces. Do not use
tabs in your code. You should set your editor to emit spaces when you hit
the tab key.
cp foo bar
cp some_reallllllllly_realllllllllllllly_long_path \
to_another_really_long_path
6. If, For, and While
To match Kernighan and Ritchie style, the sh token equivalent to the C "{"
should appear on the same line, separated by a ";", as in:
if [ $x = 'something' ]; then
echo "$x"
fi
for i in 1 2 3; do
echo $i
done
while [ $# -gt 0 ]; do
echo $1
shift
done
7. Use of Shell Builtin Commands
If possible shell buitins should be preferred to external utilities. Each
call of test true sed awk etc generates a new process. Used in a loop this
can extend the execution time considerably. So please do not write:
if test $# -gt 0; then
Instead use:
if [ $# -gt 0 ]; then
In the following example the shell parameter expansion is used to get the
base name and the directory of a path:
for pathname in $(find -type f -name "*" -print); do
basename=${pathname##*/} # replaces basename
dirname=${pathname%/*} # replaces dirname
dirlength=${#dirname} # expr length
done
The proper way to write an infinite loop in the shell is to use the ":"
built-in, which evaluates to true (exit status 0). This is better than
using "true", because that is *not* a built-in and thus runs /bin/true.
while :; do
echo infinite loop
done
Do not test for non-/empty strings by comparing to "" or ''. always use
the test operators -n (non-zero-length string) and -z (zero-length string).
if [ -z "$foo" ]; then
echo 'you forgot to set $foo'
fi
if [ -n "$BASEDIR" ]; then
echo "\$BASEDIR is set to $BASEDIR"
fi
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BASH CODING STYLE
skid@vestacp.com
2011.12.28
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