shell脚本里常见的指令和函数

shell script可以执行cd指令改变当前目录

[root@demo1 test]# vi test.sh cd /home touch go echo haha > go ls go cd /home/mac echo haha > aa

[root@demo1 test]# sh test.sh go [root@demo1 test]# ls /home go  guan  iei  mac [root@demo1 test]# cat /home/go haha [root@demo1 test]# cat ../aa haha

   shell script下对当前路径的处理——$PWD, 但此值随cd指令而变，因此建议保存在另一个变量中

[root@nm ntshellhttp]# vi test.sh #!/bin/bash a="$PWD" echo $a cd / ls $a

    每隔5秒(sleep 5)就做一些操作,如果用while语句的话,应该如何设置?

echo "input num:" read num echo "input is $num" while test $num -lt 10 do num=$(($num+1)) echo "new num is $num" sleep 5 done

[root@mac-home macg]# sh test.sh input num: 3 input is 3 new num is 4 new num is 5 new num is 6 new num is 7 new num is 8 new num is 9

  Shell的 exit命令
if
exit 1
else
exit 0    脚本退出并返回代码1


    菜单显示，不必多个echo一行行显示，可以一整个echo

echo "=============================================== |           ** unix script test               | |           1 --- num 1                       | |           2 --- num 2                       | |           3 --- num 3                       | |           4 --- num 4                       | ==============================================="

  更简单的菜单显示---------echo函数化

banner(){ echo "=============================================== |           ** unix script test             | |           1 --- num 1                       | |           2 --- num 2                       | |           3 --- num 3                       | |           4 --- num 4                       | ===============================================" } 引用函数，显示菜单 banner

    输入y,n函数

getyn()                              { while echo "enter y/n :" do  read yn  case $yn in   [Yy]) return 0 ;;   yes) return 0 ;;   YES) return 0 ;;   [Nn]) return 1 ;;   no) return 1;;   NO) return 1;;   * ) echo "only accept Y,y,N,n,YES,yes,NO,no";;  esac done }

    pause函数-----------输入回车继续，输入q退出程序，其他值pause

pause() { while echo "Press to proceed or type q to quit:" do read cmd case $cmd in  [qQ]) exit 1;;     直接退到底，退出shell script  "") break;;        break跳出while语句                            引号中间没有任何字符，表示是return  *) continue;;      continue继续下一循环 esac done

    用上面的函数构成的标准的输入script例子

while getyn                 command作为条件 do  banner done

[macg@mac-home ~]$ ./test.sh enter y/n : d only accept Y,y,N,n,YES,yes,NO,no         enter y/n : y                                             =============================================== |           ** unix script test               | |           1 --- num 1                       | |           2 --- num 2                       | |           3 --- num 3                       | |           4 --- num 4                       | =============================================== enter y/n :           n          输入n,getyn函数返回1，1为假，跳出循环                              [macg@mac-home ~]$

   一个开机自动启动HTTP和MYSQL的script

[root@mac-home macg]# vi server.sh : if [ -f /var/run/httpd.pid ]    如果存在/var/run/httpd.pid,就显示其内容 then cat /var/run/httpd.pid else /etc/init.d/httpd start       如果不存在/var/run/httpd.pid，就启动http fi if [ -f /var/run/mysqld/mysqld.pid ] then cat /var/run/mysqld/mysqld.pid else /etc/init.d/mysqld start fi

[root@mac-home macg]# sh server.sh        Starting httpd: [  OK  ]                               Starting MySQL:  [  OK  ] [root@mac-home macg]# sh server.sh         12944           13044

   一个从文件中删除某行的shell函数rmline_from_file()
例子：从rc.local中删除含有 "root/bridge"的行

[root@demo1 test]# vi rmline_from_file #!/bin/sh rmline_from_file() { [ -f temp.file ] && rm -f temp.file while read LINE        每次从$1的文件里读一行，在do里处理  do   if     echo $LINE|grep $2  >/dev/null 2>&1   then     continue   else     echo $LINE >> temp.file   fi  done < $1 rm -f $1 mv temp.file $1 }

rmline_from_file rc.local /root/bridge $1是要处理的文件名 $2是要删除的行含有的pattern(用于grep 出行)

    Command <
将多行文字传递给前面的command
一般用于显示帮助

cat < ... ... HELP

   例2 一个简单的help函数

[macg@machome ~]$ vi test.sh help() { cat <USAGE: xtitlebar [-h] "string_for_titelbar" OPTIONS: -h help text EXAMPLE: xtitlebar "cvs" HELP exit 0 } help

[macg@machome ~]$ sh test.sh USAGE: xtitlebar [-h] "string_for_titelbar" OPTIONS: -h help text EXAMPLE: xtitlebar "cvs"