shell functions study notes 7-shell-

First, the function

　　1. What is the shell functions

　　　　The same definition of a function block, the code amount can be reduced throughout the program to improve development efficiency

　　　　Increase readability and legibility of the program, improve management efficiency

　　　　Failure can program features a modular, so that the program has portability

　　　　In fact, linux system which nearly 2,000 commands can be said is a function of the shell

　　2, Grammar

　　　　function name () compound command block [redirection]

function function name () {#function negligible written 
    instructions. . . 
    exit and return n # Similarly, return is a function of exit 
}

　　3, based on practice

　　　　1) Develop a build two simple function calls and execution

[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) and the number of execution script file line separation function body

[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, enterprise-class URL checking scripts

　　　　Participation by the mass function into a script file transfer command line parameters to determine whether there is any specified url removed

　　　　1) Practice script parameter passing, to check whether the normal web URL

[root @ web1 scripts] # CAT test23. SH  
# pass parameters to determine whether the format is 1 
# ! / bin / bash 

IF [$ # -en 1 ]    
 # "$ #" get back the total number of parameters of the currently executing script access
         the then 
                echo $ " Usage: $ 0 url " 
                Exit 1 
fi 

wget --spider -q -o / dev / null --tries = 1 -T 5 $ 1 
#T timeout practice, where $ 1 is the parameter script 
IF [$? -eq 0 ]
 # "$ ?" get on a return instruction execution status value, 0 on success, nonzero failure
         the then 
                echo  " $ 1 iS yes "
        else
                echo "$1 is no"
fi

 

　　　　2) The above detection function written as a function, the function and parameter passing is converted into a script transmission command line parameters, determines whether or not any abnormality specified URL

! # / bin / the bash
 function Usage () {
         echo $ " Usage: $ 0 URL " 
        Exit . 1 
} 

function check_url () {    # URL detection function
         wget --spider -q -o / dev / = Full --tries . 1 -T 5 $ 1 
# this is the function parameter passing $ 1 
        if [$? -eq 0 ]
                 the then 
                        echo  " $ 1 iS Yes " 
        the else             
                        echo  " $ 1 iS NO " 
        Fi 

} 

function main () {     # main function
         if[$ # -Ne . 1 ]
 # If a plurality of parameters passed, print help function, the user prompts
                 the then 
                        Usage 
        Fi 
        check_url $ . 1 } 
# receiving transfer function parameters, i.e. below the end of the main $ * cominghere 
main $ * 
# $ * here is to put all the parameters as a function of the received command line parameter to an internal function, it is a common transceiver 

　　operation result

[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) The transfer function of the reference conversion layer script file transfer command line parameters, determined arbitrarily designated url whether there is abnormality, and is displayed in more specialized

! # / 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 ]
    the then 
     Action " $ 1 iS yes. " / bin / to true　　　　　　#action is to call the library functions
   the else 
     Action " $ 1 iS NO. " / bin /false
  fi
}

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

 　　　　effect

[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, the use of shell functions developed a key optimization system script

　　　　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

　　　　not up-to-date

　　6, the use of shell functions developed rsync service startup script

 

#!/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

 

 

 

Reference to learn: https://blog.51cto.com/oldboy/1855639