Read of Linux built-in commands

I. The role of Read

Read to save the user's keyboard input string in the following variables

[[email protected] scripts]# read Num1[[email protected] scripts]# echo $Num 1[[email protected] scripts]# read Num123[[ema Il protected] scripts]# echo $Num 123

You can enter any information to the script through read, or you can read multiple values from the command line to the variable

[[email protected] scripts]# Read Num Name Year1 arvin 2015[[email protected] scripts]# echo $Num $Name $Year 1 Arvin 2015

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[[email protected] scripts]# Read Num Name Year1 arvin 2014[[email protected] scripts]# echo $Num 1[[email protected] scripts]# echo $NameArvin [[email protected] scripts]# echo $Year #这里把最后两个字符传递给了变量Year

Second, read common parameters

-P (): Added hint message # Another echo-n after displaying the information, does not break the line

-T: Specifies the time-out period, in which the read command does not interact, and the timeout exits

Iii. Examples and Exercises

Example 1:

#!/bin/bash#read–p "Input a character:" Charcase $Char in[0-9]) echo "a digit.";;        [A-z]) echo "A lower.";;        [A-z]) echo "A Upper.";;        [[:p UNCT:]]) echo "A punction.";; *) echo "A special char."; Esac

Example 2 :

#!/bin/bash#read-p "Do you agree [Yes|no]?:" Yesnocase $YesNo iny| y| [Yy]es] echo "agreed, proceed.";; n| n| [Nn]o] echo "disagreed, can ' t proceed."; *) echo "Invalid input.";; Esac

Example 3: Write a script
1. Display the following menu to the user:
m| M) show memory usages;
d| D) show disk usages;
q| Q) quit
2. If the user selects the first item, the memory usage information is displayed;
If the second item is selected, the disk mount and usage information is displayed;
If it is the third item, exit and show opt-out;
Any other content that describes the error options;

#!/bin/bash#cat << eofm| M) Show Memory usages;d| D) Show Disk usages;q| Q) quiteofread-t 20-p "Press a choice:" Keyif [-Z $Key];    Then echo "No choice,quit." Key=q Exit 3ficase $Key inm| M) free-m;; d| D) Du-lh;; q|    Q) echo "Quit." Exit 5;;    *) echo "Invalid input." ;; Esac

Exercise 1

#!/bin/bash# date: 2015-04-13# description:# version: 1.0if [ ! -e  /backup ];then     #这里可以用 [ -d /backup ] | |  mkdir /backup  substitution     mkdir /backupfiread -t 20 -p  "Press a command{gzip|bzip2|xz}:"  Command     #read, 20 seconds timeout, assign command value command= $1if [ -z $1 ]; then     #如果脚本给定的是空值, the default input gzip     Command=gzipficase  $Command  ingzip)     tar czfp /backup/ backupfile-' date +%f-%h-%m-%s ' .tar.gz /etc/    ret=$?    ;; bzip2)     tar cjfp /backup/backupfile-' date +%f-%h-%m-%s '. tar.bz2 /etc /    ret=$?    ;; XZ)     tar cjfp /backup/backupfile-' date +%f-%h-%m-%s '. tar.xz /etc/    Ret=$?    ;; *)     echo  "Usage: ' basename $0 ' {gzip | bzip2 | xz }."     exit 5    ;; esac    [  $Ret  -eq 0 ] && echo  "backup etc  successfully. ($Command) "     #通过每个循环分支的返回值

This article is from the "Arvin Lau" blog, be sure to keep this source http://64314491.blog.51cto.com/2784219/1631952

Read of Linux built-in commands