如何将shell script功能模块化，并且对外留出函数和参数接口

如何将shell script功能模块化，并且对外留出函数和参数接口。要写出这种高质量的模块化的东西，需要对要写的这一块的业务非常理解，知道哪些是通用的，哪些是不通用的。从而将其分离，废话不多说直接看一个我感觉很牛B的脚本。

以下脚本的作用：
我新写了一个内核device driver模块，下面的脚本是尝试将我的模块，加载模块，在/dev目录下创建结点+++删除文件，卸载模块。

参数接口部分：

#!/bin/bash
# Sample init script for the a driver module <rubini@linux.it>

DEVICE="scull"
SECTION="misc"

# The list of filenames and minor numbers: $PREFIX is prefixed to all names
PREFIX="scull"
FILES="     0 0         1 1         2 2        3 3    priv 16
        pipe0 32    pipe1 33    pipe2 34   pipe3 35
       single 48      uid 64     wuid 80"

INSMOD=/sbin/insmod; # use /sbin/modprobe if you prefer

function device_specific_post_load () {
    true; # fill at will
}
function device_specific_pre_unload () {
    true; # fill at will
}

具体介绍：

• DEVICE是加载的模块的名字。必须和在driver代码中注册的名字相同。
• FILES是加载的模块生成的文件参数。（文件名字后缀+minor_num）。

最虎的是：
留出了2个函数接口，让我们面向接口编程。
留出的2个接口是device_specific_post_load 和 device_specific_pre_unload分别是insmod加载之后想做什么？rmmod之后想做什么？这种面向接口编程主要是对实际应用的人考虑的比较周到。

 

下面这个是一些不轻易被用户改变的参数：

# Everything below this line should work unchanged for any char device.
# Obviously, however, no options on the command line: either in
# /etc/${DEVICE}.conf or /etc/modules.conf (if modprobe is used)

# Optional configuration file: format is
#    owner  <ownername>
#    group  <groupname>
#    mode   <modename>
#    options <insmod options>
CFG=/etc/${DEVICE}.conf

# kernel version, used to look for modules
KERNEL=`uname -r`

#FIXME: it looks like there is no misc section. Where should it be?
MODDIR="/lib/modules/${KERNEL}/kernel/drivers/${SECTION}"
if [ ! -d $MODDIR ]; then MODDIR="/lib/modules/${KERNEL}/${SECTION}"; fi

# Root or die
if [ "$(id -u)" != "0" ]
then
  echo "You must be root to load or unload kernel modules"
  exit 1
fi

# Read configuration file
if [ -r $CFG ]; then
    OWNER=`awk "\\$1==\"owner\" {print \\$2}" $CFG`
    GROUP=`awk "\\$1==\"group\" {print \\$2}" $CFG`
    MODE=`awk "\\$1==\"mode\" {print \\$2}" $CFG`
    # The options string may include extra blanks or only blanks
    OPTIONS=`sed -n '/^options / s/options //p' $CFG`
fi

主要包括取得config file里面的用户权限信息，检查用户是否为root用户。

# Create device files
function create_files () {
    cd /dev
    local devlist=""
    local file
    while true; do
        if [ $# -lt 2 ]; then break; fi
        file="${DEVICE}$1"
        mknod $file c $MAJOR $2
        devlist="$devlist $file"
        shift 2
    done
    if [ -n "$OWNER" ]; then chown $OWNER $devlist; fi
    if [ -n "$GROUP" ]; then chgrp $GROUP $devlist; fi
    if [ -n "$MODE"  ]; then chmod $MODE  $devlist; fi
}

# Remove device files
function remove_files () {
    cd /dev
    local devlist=""   //函数里的变量尽量使用local关键字声明，代表是一个局部变量
    local file
    while true; do
        if [ $# -lt 2 ]; then break; fi
        file="${DEVICE}$1"
        devlist="$devlist $file"
        shift 2
    done
    rm -f $devlist
}

# Load and create files
function load_device () {

    if [ -f $MODDIR/$DEVICE.o ]; then
        devpath=$MODDIR/$DEVICE.o
    else if [ -f ./$DEVICE.o ]; then
        devpath=./$DEVICE.o
    else
        devpath=$DEVICE; # let insmod/modprobe guess
    fi; fi
    if [ "$devpath" != "$DEVICE" ]; then
        echo -n " (loading file $devpath)"
    fi

    if $INSMOD $devpath $OPTIONS; then
        MAJOR=`awk "\\$2==\"$DEVICE\" {print \\$1}" /proc/devices`
        remove_files $FILES
        create_files $FILES
        device_specific_post_load
    else
        echo " FAILED!"
     fi
}

# Unload and remove files
function unload_device () {
    device_specific_pre_unload
    /sbin/rmmod $DEVICE
    remove_files $FILES
}

上面的4个是函数。create_files, remove_files, load_device, unload_device
下面的就是case语句进行选择运行了。

case "$1" in
  start)
     echo -n "Loading $DEVICE"
     load_device
     echo "."
     ;;
  stop)
     echo -n "Unloading $DEVICE"
     unload_device
     echo "."
     ;;
  force-reload|restart)
     echo -n "Reloading $DEVICE"
     unload_device
     load_device
     echo "."
     ;;
  *)
     echo "Usage: $0 {start|stop|restart|force-reload}"
     exit 1
esac

exit 0