Eg32、while/until/for经典例子

#!/bin/bash

## filename: while-infinite_loops.sh

while true; do

    sleep 5

    echo "infinite loops [ hit CTRL+C to stop]"

done

Eg33、while/until/for经典例子

#!/bin/bash

## filename: until-infinite_loops.sh

until false; do

    sleep 5

    echo "infinite loops [ hit CTRL+C to stop]"

done

Eg34、while/until/for经典例子

#!/bin/bash

## filename: for-infinite_loops.sh

for (( ; ; )); do

    sleep 5

    echo "infinite loops [ hit CTRL+C to stop]"

done

具体执行都是一样的：

Eg35、将循环接管通过管道传递给其他命令（done |）

#!/bin/bash

## filename: loop--to_pipe.sh

for i in 7 8 9 2 3 4 5 11; do

        echo $i

done | sort -n

awk -F':' '$3 >= 500 {print $1}' /etc/passwd |

while IFS= read -r person

do

    echo $person

done | sort

##该 awk 命令从 /etc/passwd 文件中筛选出 UID 大于等于 500 的行，并仅输出这些行的用户名。

awk 是一个强大的文本分析工具，用于逐行处理输入文件。

-F: 指定了字段分隔符为冒号（:），这是 /etc/passwd 文件中各字段间的分隔符。

'$3 >= 500 {print $1}' 是 awk 的脚本部分：

• $3 >= 500 是条件表达式，检查每一行的第三个字段（即UID）是否大于等于 500。
• {print $1} 是满足条件时执行的动作，打印当前行的第一个字段（即用户名）。

Eg36、后台执行循环（done &）

#!/bin/bash

## filename: loop--in_background.sh

nobody=xh_ry@163.com

linux=38742777@qq.com

for person in $linux $nobody

do

     #mail -s "Test" $person < "Hello  everyone"

     echo "hi,ih" | mail -s "test loop-in-backgroud" $person

done &

awk -F':' '$3 >= 500 {print $1}' /etc/passwd |

while IFS= read -r person

do

    mail -s "2nd mail test" $person <<-END

        Hello $person,

            This message is from $(hostname -f).

                         $USER   $(date +%F)

        END

done &

执行后会发送邮件给nobody和linux，注意第二段的脚本需要执行mail -s交互性操作。可以分离输入。

Eg37、while实现循环菜单

#!/bin/bash

## filename: what-lang-do-you-like_while.sh

while :

do

  echo "====== Scripting Language ======"

  echo "1) bash"

  echo "2) perl"

  echo "3) python"

  echo "4) ruby"

  echo "5) (Quit) "

  read -p "What is your preferred scripting language?  " lang

  case $lang in

    1|bash)     echo "You selected bash"  ;;

    2|perl)     echo "You selected perl"  ;;

    3|python)   echo "You selected python";;

    4|ruby)     echo "You selected ruby"  ;;

    5|quit)     break ;;

  esac

done

Eg38、select实现循环菜单1。

#!/bin/bash

## filename: what-lang-do-you-like_select.sh

clear

PS3="What is your preferred scripting language?  "

select s in bash perl python ruby quit

do

  case $s in

    bash|perl|python|ruby) echo "You selected $s"  ;;

    quit) break  ;;

       *) echo "You selected error , retry …" ;;

  esac

done

Eg39、select实现循环菜单2。

#!/bin/bash

## filename: what-os-do-you-like_select.sh

clear

PS3="What is your preferred OS? "

IFS='|'

os="Linux|Gnu Hurd|FreeBSD|Mac OS X"

select s in $os

do

  case $REPLY in

    1|2|3|4) echo "You selected $s"  ;;

          *) break ;;

  esac

done

Eg40、select实现循环菜单3。

#!/bin/bash

## filename: /root/bin/xtop

## filename: what-cmd-do-you-want_select.sh

PS3="Select a program you want to execute: "

TOPLIST="top htop atop nettop jnettop iftop ftop iotop mytop innotop dnstop apachetop"

clear

select prog in $TOPLIST quit

do

    [[ $prog == quit ]] && exit

    apt list --installed $prgo 2>&1 > /dev/null

    #dpkg -s $prog > /dev/null

    #rpm -q $prog > /dev/null &&

        $prog || echo " $prog is not installed."

done

rpm是redhat/rhel下的，dpkg是debian下的检测包安装命令

执行如下：

选择1后，

q退出后继续选择3，6，9，13结束。

Eg41、for遍历-参数个数-实例

#!/bin/bash

## filename: pp_traverse_1.sh

# Usage: pp_traverse_1.sh [arguments]

#

echo "The name of this script is: `basename $0`"

echo "The arguments are: $*"

echo "The number of arguments is: $#"

for i ; do  echo "$i" ; done

num=1

for i ; do

  echo "The ${num}th argument is: $i"

  ((num++))

done

Eg42、while实现-参数遍历实例

#!/bin/bash

## filename: pp_traverse_2.sh

# This script is to test command line arguments

# Usage: pp_traverse_2.sh [arguments]

#

echo "----- using the first kind of method ---- "

num=1

while [ $num -le $# ]

do

  # eval para=\$$num

  # echo "The ${num}th argument is: $para"

  echo "The ${num}th argument is: ${!num}"

  let num=num+1

done

echo "----- using the second kind of method --- "

for (( num=1 ; num <= $# ; num++)) ; do

  echo "The ${num}th argument is: ${!num}"

done

Eg43、使用_shift_while遍历的实例

#!/bin/bash

## filename: pp_traverse_shift_while.sh

# Usage: pp_traverse_shift_while.sh [arguments]

#

echo "using while loop to traverse positional parameter"

#while [[ "$1" ]] ; do

#    echo "$1"

#    shift

#done

num=1

while [[ "$1" ]] ; do

    echo "The ${num}th argument is: $1"

    let num=num+1

    shift

done

Eg44、使用_shift_until遍历的实例

#!/bin/bash

## filename: pp_traverse_shift_until.sh

# Usage: pp_traverse_shift_until.sh [arguments]

#

echo "using until loop to traverse positional parameter"

#until [ -z "$1" ] ; do

#    echo "$1"

#    shift

#done

num=1

until [ -z "$1" ]

do

    echo "The ${num}th argument is: $1"

    ((num++))

    shift

done

Eg45、使用_shift_for遍历的实例

#!/bin/bash

## filename: pp_traverse_shift_for.sh

# Usage: pp_traverse_shift_for.sh [arguments]

#

echo "using for loop to traverse positional parameter"

#for (( ; ; )) ; do

#    [ -n "$1" ] &&  echo "$1" || break

#    shift

#done

for (( num=1 ; ; num++ )) ; do

    [ -n "$1" ] &&

      echo "The ${num}th argument is: $1" || break

    shift

done

Eg46、shift位置参数变量实例-实现HTM重命名为html。

#!/bin/bash

## filename: ren

if [ $# -lt 3 ] ; then

cat <<_HELP_

FUNCTION:  Renames a number of files using sed regular expressions.

USAGE:     $0 '<regexp>' '<replacement>' <files ...>

EXAMPLE:   Rename all *.HTM files to *.html:

           $0 'HTM$' 'html' *.HTM

_HELP_

exit 1

fi

OLD="$1" ; NEW="$2" ; shift ; shift  # $* contains now all the files

for file in $*; do

    if [ -f "$file" ] ; then

##检查当前文件（$file）是否存在且为普通文件（非目录、设备文件等）

      newfile=`echo "$file" | sed "s/${OLD}/${NEW}/g"`

##使用 sed 命令将文件名中的OLD变量（即传入的正则表达式）替换为##NEW变量（即替换字符串），并将新文件名赋值给变量newfile。

      if [ -f "$newfile" ]; then

        echo "ERROR: $newfile exists already."

      else

        echo "Renaming $file to $newfile."

        mv "$file" "$newfile"

      fi

##检查新文件名（$newfile）是否已存在。如果存在，输出错误信息；否

则，输出重命名信息，并使用 mv 命令将原文件名（$file）重命名为新文件名（$newfile）。

    fi

done

Eg47、getops使用分析-实例1

#!/bin/bash

## filename : pp_parse_getopts_1.sh

while getopts  "abc:def:ghi" flag

do

  echo "$flag" $OPTIND $OPTARG

done

echo "Resetting"

OPTIND=1

while getopts  "bc:def:ghi" flag

do

  echo "$flag" $OPTIND $OPTARG

Done

Eg48、getops使用分析-实例2

linux@LAPTOP-X280:~$ cat 48eg.sh

#!/bin/bash

## filename : pp_parse_getopts_1.sh

while getopts  ":abc:def:ghi" flag

do

  echo "$flag" $OPTIND $OPTARG

done

echo "Resetting"

OPTIND=1

while getopts  ":bc:def:ghi" flag

do

  echo "$flag" $OPTIND $OPTARG

done

Eg49、getops使用分析-实例3-

#!/bin/bash

## filename : mybackup_getopts.sh

while getopts :zc:x:rv opt

do

  case $opt in

    c) ConfFile=$OPTARG       ;;

    x) ExcludeFile=$OPTARG    ;;

    z) Compress=true          ;;

    r) Recursive=true         ;;

    v) Verbose=true           ;;

    :)

      echo "$0: Must supply an argument to -$OPTARG." >&2

      exit 1

      ;;

    \?) echo "Invalid option -$OPTARG ignored." >&2   ;;

  esac

done

shift $((OPTIND-1)) ; echo $0 ; echo "$@"

<--undo-->

Eg50、getops使用分析-实例4-

#!/bin/bash

## filename : mybackup_getopts2.sh

while getopts :zc:x:rv opt

do

  case $opt in

    c) if [[ $OPTARG = -* ]]; then  ((OPTIND--)) ;  continue ;  fi

       ConfFile=$OPTARG       ;;

    x) ExcludeFile=$OPTARG    ;;

    z) Compress=true          ;;

    r) Recursive=true         ;;

    v) Verbose=true           ;;

    :)

      echo "$0: Must supply an argument to -$OPTARG." >&2

      exit 1

      ;;

    \?) echo "Invalid option -$OPTARG ignored." >&2   ;;

  esac

done

shift ((OPTIND-1)) ; echo $0 ; echo "$@"

<--undo-->

Eg51、函数实现的backup菜单

#!/bin/bash

## filename: all_in_one_backup_select.sh

### User define Function (UDF) ###

sql_bak  () { echo "Running mysqldump tool..."; }

sync_bak () { echo "Running rsync tool..."; }

git_bak  () { echo "Running gistore tool..."; }

tar_bak  () { echo "Running tar tool..."; }

### Main script starts here ###

PS3="Please choose a backup tools : "

select s in  mysqldump rsync gistore tar quit ; do

  case $REPLY in

       1) sql_bak  ;;

       2) sync_bak ;;

       3) git_bak  ;;

       4) tar_bak  ;;

       5) exit     ;;

  esac

done

Eg52、函数的局部变量例子

#!/bin/bash

## filename: pp_and_function.sh

echo "===Print positional parameters in main :"

echo "$0: $*"

pp1(){

  echo 'f1--Print $* parameters in fun1 :' ; echo "$0: $*"

}

pp2(){

  echo 'f2--Print $* parameters in fun1 :' ; echo "$0: $*"

  pp1 1st 2nd 3th 4th 5th 6th 7th 8th 9th

  echo 'f2--Print $* parameters in fun1 :' ; echo "$0: $*"

}

pp1 1 2 3 4 5 6 7 8 9

echo "===Print positional parameters in main :"

echo "$0: $*"

pp2 I II III IV V VI VII VIII IX

Eg53、位置参数函数-比大小

#!/bin/bash

## filename: function_max.sh

# User define Function (UDF)

usage () {

  echo "List the MAX of the positive integers in command line. "

  echo "Usage: `basename $0` <num1> <num2> [ <num3> ... ]"

  exit

}

max () {

  [[ -z $1 || -z $2 ]] && usage

  largest=0

  for i ; do  ((i>largest)) && largest=$i ; done

}

### Main script starts here ###

max "$@"

echo "The largest of the numbers is $largest."

Eg54、函数的返回值调用-实例

#!/bin/bash

## filename: function_max2.sh

# User define Function (UDF)

max2 () {

  if [[ -z $1 || -z $2 ]] ; then

    echo  "Need 2 parameters to the function." ; exit

  fi

  [ $1 -eq $2 ] &&

       { echo "The two numbers are equal." ; exit ; }

  (($1>$2)) && return $1 || return $2

}

### Main script starts here ###

read -p "Please input two integer numbers  : " n1 n2

echo "n1=$n1 , n2=$n2"

max2 $n1 $n2

return_val=$?

echo "The larger of the two numbers is $return_val."

Eg55、标准输出返回函数值

#!/bin/bash

## filename: function_to-upper.sh

# User define Function (UDF)

to_upper () {

    local str="$@"

    local output

    output=$(tr '[a-z]' '[A-Z]'<<<"${str}")

    echo $output

}

### Main script starts here ###

to_upper "This Is a TEST"

res=$(to_upper "$@")

echo "$res"

res=$(to_upper "$1")

[[ $res == "YES" ]] && echo "Continue..." || echo "Stop"