shell 学习笔记7-shell-函数

一、函数

  1、什么是shell函数

    把相同程序段定义成函数,可以减少整个程序的代码量,提升开发效率

    增加程序的可读性,易读性,提升管理效率

    可以失效程序功能模块化,使程序具备可移植性

    其实linux系统里面近2000个命令可以说都是shell的函数

  2、语法

    function 名称() 复合命令块[重定向]

function 函数名 () {    #function可以忽略不写
    指令。。。
    return n         #和exit类似,return是退出函数
}

  3、基础实践

    1)开发一个建立两个简单函数并调用执行

[root@web1 scripts]# cat test21.sh 
#!/bin/bash
boy(){
        echo "i am boy"
}
function girl(){
        echo "i am girl"
}
boy
girl
[root@web1 scripts]# ./test21.sh 
i am boy
i am girl
[root@web1 scripts]# cat test21-1.sh 
#!/bin/bash
boy(){
        echo "i am boy"
}
function girl(){
        echo "i am girl"
}
boy
girl
boy1
[root@web1 scripts]# ./test21-1.sh 
i am boy
i am girl
./test21-1.sh: line 10: boy1: command not found
[root@web1 scripts]# 

  2)分离函数体和执行行数的脚本文件

[root@web1 scripts]# cat >>/etc/init.d/functions<<- EOF
> boy(){
> echo "i am boy"
> }
> EOF
[root@web1 scripts]# !tail
tail -3 /etc/init.d/functions
boy(){
echo "i am boy"
}
[root@web1 scripts]# 
[root@web1 ~]# function boy1 {
> echo "i am boy1"
> }

 [root@web1 scripts]# boy1
 i am boy1

  4、实现企业级URL检查脚本

    经函数的传参换成脚本文件命令行传参,判断任意指定的url是否存在移除

    1)实践脚本传参,检查web URL是否正常

[root@web1 scripts]# cat test23.sh 
#判断传参格式是否为1
#!/bin/bash

if [ $# -en 1 ]    
#“$#”获取当前执行的脚本后面接的参数总个数
        then
                echo $"usage:$0 url"
                exit 1
fi

wget --spider -q -o /dev/null --tries=1 -T 5 $1
#T超时实践,这里的$1为脚本的参数
if [ $? -eq 0 ]
#“$?”获取上一个指令的执行状态返回值,0成功,非零失败
        then
                echo "$1 is yes"
        else
                echo "$1 is no"
fi

 

    2)将上述检测的功能写成函数,并将函数传参转换成脚本命令行传参,判断任意指定的URL是否存在异常

#!/bin/bash
function usage(){
        echo $"usage:$0 url"
        exit 1
}

function check_url(){   #检测URL函数
        wget --spider -q -o /dev/full --tries=1 -T 5 $1
#这里$1就是函数传参
        if [ $? -eq 0 ]
                then
                        echo "$1 is yes"
        else            
                        echo "$1 is no"
        fi

}

function main(){    #主函数
        if [ $# -ne 1 ]
#如果传入的是多个参数,则打印帮助函数,提示用户
                then
                        usage
        fi
        check_url $1 
} #接收函数的传参,即把下文main结尾的$*
传到这里 main $* #这里的$*就是把命令行接收的所有参数作为函数参数传给函数内部,是一种常用收发

  运行结果

[root@web1 scripts]# sh test24.sh  www.baidu.com
www.baidu.com is yes
[root@web1 scripts]# sh test24.sh  www.baidu1.com
www.baidu1.com is no
[root@web1 scripts]# 

   3)将函数的传参转换层脚本文件命令行传参,判断任意指定的url是否存在异常,并以更专业的显示

#!/bin/sh
. /etc/init.d/functions            

function usage(){
  echo $"usage:$0 url"
  exit 1
}

function check_url(){
  wget --spider -q -o /dev/null --tries=1 -T 5 $1
  if [ $? -eq 0 ]
   then
     action "$1 is yes." /bin/true      #action 就是调用函数库的函数
  else
     action "$1 is no." /bin/false
  fi
}

function main(){
  if [ $# -ne 1 ]
   then
     usage
  fi
  check_url $1
}
main $*

     效果

[root@web1 scripts]# chmod +x test25.sh
[root@web1 scripts]# ./test25.sh  www.baidu.com
www.baidu.com is yes.                                      [  OK  ]
[root@web1 scripts]# ./test25.sh  www.baidu1.com
www.baidu1.com is no.                                      [FAILED]
[root@web1 scripts]# 

 

  5、利用shell函数开发一键优化系统脚本

    centos6

#!/bin/bash
# author:oldboy
# qq:31333741
#set env
export PATH=$PATH:/bin:/sbin:/usr/sbin
# Require root to run this script.
if [ "$UID" != "0" ]; then
    echo "Please run this script by root."
    exit 1
fi

#define cmd var
SERVICE=`which service`
CHKCONFIG=`which chkconfig`

function mod_yum(){
    #modify yum path
    if [ -e /etc/yum.repos.d/CentOS-Base.repo ]
     then
       mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup&&\
       wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo 
    fi
}

function close_selinux(){
    #1.close selinux
    sed -i 's/SELINUX=enforcing/SELINUX=disabled/' /etc/selinux/config
    #grep SELINUX=disabled /etc/selinux/config 
    setenforce 0 &>/dev/null
    #getenforce
}

function close_iptables(){
    #2.close iptables 
    /etc/init.d/iptables stop
    /etc/init.d/iptables stop
    chkconfig iptables off
}

function least_service(){
    #3.least service startup
    chkconfig|awk '{print "chkconfig",$1,"off"}'|bash
    chkconfig|egrep "crond|sshd|network|rsyslog|sysstat"|awk '{print "chkconfig",$1,"on"}'|bash
    #export LANG=en
    #chkconfig --list|grep 3:on
}

function adduser(){
    #4.add oldboy and sudo
    if [ `grep -w oldboy /etc/passwd|wc -l` -lt 1 ]
      then
        useradd oldboy
        echo 123456|passwd --stdin oldboy
        \cp /etc/sudoers /etc/sudoers.ori
        echo "oldboy  ALL=(ALL) NOPASSWD: ALL " >>/etc/sudoers
        tail -1 /etc/sudoers
        visudo -c &>/dev/null
    fi
}

function charset(){
    #5.charset config
    cp /etc/sysconfig/i18n /etc/sysconfig/i18n.ori
    echo 'LANG="zh_CN.UTF-8"'  >/etc/sysconfig/i18n 
    source /etc/sysconfig/i18n
    #echo $LANG
}

function time_sync(){
    #6.time sync.
    cron=/var/spool/cron/root
    if [ `grep -w "ntpdate" $cron|wc -l` -lt 1  ]
      then
        echo '#time sync by oldboy at 2010-2-1' >>$cron
        echo '*/5 * * * * /usr/sbin/ntpdate time.nist.gov >/dev/null 2>&1' >>$cron
        crontab -l
    fi
}

function com_line_set(){
    #7.command set.
    if [ `egrep "TMOUT|HISTSIZE|HISTFILESIZE" /etc/profile|wc -l` -ge 3  ]
      then
        echo 'export TMOUT=300' >>/etc/profile
        echo 'export HISTSIZE=5' >>/etc/profile
        echo 'export HISTFILESIZE=5' >>/etc/profile
        . /etc/profile
    fi
}

function open_file_set(){
    #8.increase open file.
    if [ `grep 65535 /etc/security/limits.conf|wc -l` -lt 1 ]
      then  
        echo '*               -       nofile          65535 ' >>/etc/security/limits.conf 
        tail -1 /etc/security/limits.conf 
    fi
}

function set_kernel(){
    #9.kernel set.
    if [ `grep kernel_flag /etc/sysctl.conf|wc -l` -lt 1 ]
      then
        cat >>/etc/sysctl.conf<<EOF
        #kernel_flag
        net.ipv4.tcp_fin_timeout = 2
        net.ipv4.tcp_tw_reuse = 1
        net.ipv4.tcp_tw_recycle = 1
        net.ipv4.tcp_syncookies = 1
        net.ipv4.tcp_keepalive_time = 600
        net.ipv4.ip_local_port_range = 4000    65000
        net.ipv4.tcp_max_syn_backlog = 16384
        net.ipv4.tcp_max_tw_buckets = 36000
        net.ipv4.route.gc_timeout = 100
        net.ipv4.tcp_syn_retries = 1
        net.ipv4.tcp_synack_retries = 1
        net.core.somaxconn = 16384
        net.core.netdev_max_backlog = 16384
        net.ipv4.tcp_max_orphans = 16384
        net.nf_conntrack_max = 25000000
        net.netfilter.nf_conntrack_max = 25000000
        net.netfilter.nf_conntrack_tcp_timeout_established = 180
        net.netfilter.nf_conntrack_tcp_timeout_time_wait = 120
        net.netfilter.nf_conntrack_tcp_timeout_close_wait = 60
        net.netfilter.nf_conntrack_tcp_timeout_fin_wait = 120
EOF
        sysctl -p
    fi
}
function init_ssh(){
    \cp /etc/ssh/sshd_config /etc/ssh/sshd_config.`date +"%Y-%m-%d_%H-%M-%S"`
    #sed -i 's%#Port 22%Port 52113%' /etc/ssh/sshd_config
    sed -i 's%#PermitRootLogin yes%PermitRootLogin no%' /etc/ssh/sshd_config
    sed -i 's%#PermitEmptyPasswords no%PermitEmptyPasswords no%' /etc/ssh/sshd_config
    sed -i 's%#UseDNS yes%UseDNS no%' /etc/ssh/sshd_config
    /etc/init.d/sshd reload &>/dev/null
}

function update_linux(){
    #10.upgrade linux.
    if [ `rpm -qa lrzsz nmap tree dos2unix nc|wc -l` -le 3 ]
      then
        yum install lrzsz nmap tree dos2unix nc -y
        #yum update -y
    fi
}
main(){
    mod_yum
    close_selinux
    close_iptables
    least_service
    adduser
    charset
    time_sync
    com_line_set
    open_file_set
    set_kernel
    init_ssh
    update_linux
}
main

    centos7

    未更新

  6、利用shell函数开发rsync服务启动脚本

 

#!/bin/sh
if [ $# -ne 1 ]
  then
    echo $"usage:$0{start|stop|restart}"
    exit 1
fi
if [ "$1" = "start" ]
  then
     rsync --daemon
     if [ `netstat -lntup|grep rsync|wc -l` -ge 1 ]
       then
         echo "rsyncd is started."
         exit 0
     fi
elif [ "$1" = "stop" ]
  then
     pkill rsync
     if [ `netstat -lntup|grep rsync|wc -l` -eq 0 ]
       then
         echo "rsyncd is stopped."
         exit 0
     fi
elif [ "$1" = "restart" ]
  then
    pkill rsync
    sleep 2
    rsync --daemon
else
    echo $"usage:$0{start|stop|restart}"
    exit 1
fi

 

 

 

参考学习:https://blog.51cto.com/oldboy/1855639

posted @ 2019-08-13 12:22  乐章  阅读(442)  评论(0编辑  收藏  举报