Linux shell中getopts命令学习--实现一个添加yum源的脚本

  这是本人第一次写博客，之前从一些开源技术网站上看到不少大牛和前辈们的文章，从中学习受益。本着开源界的奉献和学习精神，觉得有必要将自己的学习成果拿出来与大家一起交流分享，既当作是一种自我学习的总结也可能帮助到有需要的人，因此发表了该篇博客。本文主要讲述在shell中getopts命令的使用以及本人写的一个脚本小案例。由于本人技术水平和能力有限，文章中的命令说明部分主要来自于help getopts的翻译，同时会带有一些本人的主观意识，如有任何描述不对的地方，请大家批评指正。

  在日常工作中写shell脚本，往往会涉及到一些命令行选项和参数的解析，这个解析过程如果完全由自己写代码去控制实现将会有一定困难，这里给大家介绍一个命令解析工具getopts。getopts是bash shell的内建命令，作用是在shell脚本中解析由命令行传递的选项和参数（也可能传递给函数、另一个被调用的shell脚本的位置参数，关于选项或参数，后面会讲解）。getopts只支持短选项，若要解析长选项请参考getopt。

getopts命令语法:

getopts optstring name [arg]

相关的术语：

  选项（option）：GNU风格的命令选项，如：-x,-y等减号加上单个字母的为短选项；--help为长选项；

  选项的参数：某些选项之后必须尾随参数，如：-f xxx.conf，xxx.conf称为选项的参数,但-f和xxx.conf之间的空格不是必须的;

  参数：位于最后一个选项，空格之后的字符串;

  optionstring：用于匹配option的字符串，optionstring中每个字母对应的是去除减号后的option（这里指短选项）;

  [arg]：用来替代位置参数被getopts解析的，类似于将$@赋值给arg;

  OPTIND: getopts的一个内置变量，表示下一个要处理的参数索引，每次shell或shell脚本执行的时候初始化为1;

  name: getopts每解析到一个选项，都会将该选项对应的字符复制给name变量.

getopts命令的简单解释：

  1.optstring中如果字母后面跟随着冒号，表示该字母所表示的option后面是带参数的，参数值将被赋到OPTARG变量中。如test.sh中包含：getopts "i:" name; 那么在命令行执行test.sh -i 1.1.1.1时，$name='i',$OPTARG=1.1.1.1

getopts包含两种错误处理的模式

安静模式下：

  2.optstring的第一个字符为冒号时，getopts将使用安静模式来报告错误（但不会有错误提示输出），生产环境中一般使用该模式;

  3.如果输入一个无效的字符作为选项时（optstring中没包含的字符），将‘？’赋值给name变量，该无效选项的字符赋值给OPTARG变量;

  4.如果选项要求跟随的参数没找到，getopts会将冒号":"赋值给name变量,设置OPTARG为发现的选项字符;

非安静模式下：

  5.如果getopts不处于安静模式，一个无效的选项被发现，'?'将被设置到name变量中且unset OPTARG;

  6.如果选项要求的参数没找到，'?'将被设置到name，OPTARG将被unset，错误提示信息将被打印.

退出状态：

  7.如果shell中$OPTERR环境变量值为0，getopts将关闭错误信息的打印，即使optstring中第一个字符不是冒号。默认的$OPTERR值为1;

  8.getopts一般情况下解析位置参数（$0-$9），但位置参数超过这个范围时仍然能被正确解析;

  9.如果选项被发现（匹配optionstring）返回true，如果遇到了选项的结尾或者有错误则返回false.

脚本示例:

1. 不带可选参数[arg]

#!/bin/bash
echo "OPTIND starts at $OPTIND"
while getopts ":q:p" optname
do
    case "$optname" in
    "p")
        echo "Option $optname is specified"
        ;;
    "q")
        echo "Option $optname has value $OPTARG"
        #shift 1
        shift $((OPTIND-2))
        ;;
    "?")
        echo "Unknown option $OPTARG"
        ;;
    ":")
        echo "No argument value for option $OPTARG"
        ;;
    *)
        # Should not occur
        echo "Unknown error while processing options"
        ;;
    esac
echo "OPTIND is now $OPTIND"
done

执行结果：

[root@dns1 ~]# bash test_getopts.sh -q aa -p -h
OPTIND starts at 1
Option q has value aa
OPTIND is now 3
Unknown option h
OPTIND is now 4

2. 带可选参数[arg]

#!/bin/bash
echo "OPTIND starts at $OPTIND"
while getopts ":q:p" optname "-q qarg" "-p" "-h" 
do
    case "$optname" in
    "p")
        echo "Option $optname is specified"
        ;;
    "q")
        echo "Option $optname has value $OPTARG"
        ;;
    "?")
        echo "Unknown option $OPTARG"
        ;;
    ":")
        echo "No argument value for option $OPTARG"
        ;;
    *)
        # Should not occur
        echo "Unknown error while processing options"
        ;;
    esac
echo "OPTIND is now $OPTIND"
done

执行结果：

[root@dns1 ~]# bash test_getopts.sh 
OPTIND starts at 1
Option q has value  qarg
OPTIND is now 2
Option p is specified
OPTIND is now 3
Unknown option h
OPTIND is now 4

3. 实现一个添加yum源的脚本

#!/bin/bash
#
# Descrition: this script will download the yum repo file from mirrors.163.com and epel for CENTOS/REDHAT DISTIBUTE
# Author: Gateray Jo 
# mail: [email protected]
set -e 
prog=`basename $0`
arch=`uname -m`
release=`lsb_release -r | sed 's/.*:[[:space:]]*//'`
function usage() {
cat<<eof
Usage: ./${prog} [options] [arg]
       -h: print the command help.
       -u: specified the baseurl for yum repository, must use with -ufn combination.
       -f: specified the name of local repofile(no ".repo" ext name) which place in /etc/yum.repos.d/, must use with -ufn 
           combination.
       -n: specified the repo's name in xxx.repo file, must use with -ufn combination.
       -d: specified the url of repofile which will be download to /etc/yum.repos.d/.
       By default, nothing options are specified which will download epel and 163 yum repofile.        
eof
}
function default() {
    major_rel=${release%%.*}
    # download 163 repofile
    printf "Download 163 repofile from mirrors.163.com:\n"
    wget -P /etc/yum.repos.d http://mirrors.163.com/.help/CentOS${major_rel}-Base-163.repo 
    printf "Download epel repofile from http://dl.fedoraproject.org.:\n"
    if [[ $arch = "x86_64" ]]; then
        [ ${major_rel} -eq 5 ] && rpm -ivh http://dl.fedoraproject.org/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm
        [ ${major_rel} -eq 6 ] && rpm -ivh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm    
    else 
        [ ${major_rel} -eq 5 ] && rpm -ivh http://dl.fedoraproject.org/pub/epel/5/i386/epel-release-5-4.noarch.rpm
        [ ${major_rel} -eq 6 ] && rpm -ivh http://dl.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
    fi
    return $?
}
if [[ $# -eq 0 ]]; then
    default
    exit $?
fi
while getopts ":hu:f:n:d:" optname; do
    case $optname in
    "h")
        usage && exit 0
        ;;
    "u")
        u_opt=1
        u_arg=$OPTARG
        ;;
    "f")
        f_opt=1
        u_arg=$OPTARG
        ;;
    "n")
        n_opt=1
        n_arg=$OPTARG
        ;;
    "d")
        wget -P /etc/yum.repos.d $OPTARG
        exit $?
        ;;
    "?")
        echo "Unknown option $OPTARG"
        usage && exit 1
        ;;
    ":")
        echo "It is need a option value for $OPTARG"
        usage && exit 1
        ;;
    *)
        echo 'Unknown error!' && exit 1
        ;;
    esac
done
if [[ $u_opt -eq 1 ]] && [[ $f_opt -eq 1 ]] && [[ $n_opt -eq 1 ]]; then
    if [[ ${n_arg} =~ '-' ]]; then
        echo "Invalid value for -n option, \"${n_arg}\" is include '-' character."
        exit 1
    fi
cat >> /etc/yum.repos.d/${f_arg}.repo <<eof
[${n_arg}]
name=${n_arg}
baseurl=${u_arg}
enabled=1
gpgcheck=0
eof
else
    usage && exit 1
fi

脚本的执行：

1）打印命令帮助

[root@dns1 ~]# ./load_yum_repo.sh -h
Usage: ./load_yum_repo.sh [options] [arg]
       -h: print the command help.
       -u: specified the baseurl for yum repository, must use with -ufn combination.
       -f: specified the name of local repofile(no ".repo" ext name) which place in /etc/yum.repos.d/, must use with -ufn 
           combination.
       -n: specified the repo's name in xxx.repo file, must use with -ufn combination.
       -d: specified the url of repofile which will be download to /etc/yum.repos.d/.
       By default, nothing options are specified which will download epel and 163 yum repofile.

2）不带任何选项参数时，自动下载163和epel的yum源repofile

[root@dns1 ~]# ./load_yum_repo.sh 
Download 163 repofile from mirrors.163.com:
--2015-04-04 22:23:05--  http://mirrors.163.com/.help/CentOS6-Base-163.repo
Resolving mirrors.163.com... 123.58.173.106
Connecting to mirrors.163.com|123.58.173.106|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2006 (2.0K) [application/octet-stream]
Saving to: “/etc/yum.repos.d/CentOS6-Base-163.repo”
100%[==========================================================================================>] 2,006       --.-K/s   in 0.05s   
2015-04-04 22:23:05 (39.2 KB/s) - “/etc/yum.repos.d/CentOS6-Base-163.repo” saved [2006/2006]
Download epel repofile from http://dl.fedoraproject.org.:
Retrieving http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
warning: /var/tmp/rpm-tmp.wVrCDS: Header V3 RSA/SHA256 Signature, key ID 0608b895: NOKEY
Preparing...                ########################################### [100%]
   1:epel-release           ########################################### [100%]

3）从指定的url中下载repofile

[root@dns1 ~]# ./load_yum_repo.sh -d http://mirrors.163.com/.help/CentOS6-Base-163.repo
--2015-04-04 22:13:47--  http://mirrors.163.com/.help/CentOS6-Base-163.repo
Resolving mirrors.163.com... 123.58.173.106
Connecting to mirrors.163.com|123.58.173.106|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2006 (2.0K) [application/octet-stream]
Saving to: “/etc/yum.repos.d/CentOS6-Base-163.repo”
100%[==========================================================================================>] 2,006       --.-K/s   in 0.05s   
2015-04-04 22:13:47 (40.9 KB/s) - “/etc/yum.repos.d/CentOS6-Base-163.repo” saved [2006/2006]

4）创建自定义的repofile

[root@dns1 ~]# ./load_yum_repo.sh -f test -n test -u file:///mnt 
[root@dns1 ~]# cat /etc/yum.repos.d/test.repo 
[test]
name=test
baseurl=file:///mnt
enabled=1
gpgcheck=0