BASH CODING STYLE

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Contents:

    1. Introduction
    2. Naming Convention
    3. Coments
    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. Coments
    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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