Linux-based shell programming (4)-for loop

For loop

Usage:

forindo    循环体done

So how do you build the list?

{1..100}

This will generate the list.
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Cases:

#!/bin/bash#forin {1..100};do    echo$Idone

Seq

You can also generate lists with the SEQ command

Usage:

seq [起始数 [步进长度]] 结束数

Cases:

[Root@iZ28g26851kZ~]# seq 1123456789Ten[Root@iZ28g26851kZ~]# seq 1 213579[Root@iZ28g26851kZ~]# seq123456789Ten[Root@iZ28g26851kZ~]# 

The application of SEQ in the For loop

#!/bin/bash#forin1210`;do    echo$Idone

Remember to use anti-single quotes to cause yo ~

Example: for 1 to 100 and

#!/bin/bash#sum=0forin100`;do   let sum=$sum+$Idoneecho"sum=${sum}"

Declare

As I've said before, in bash, variables are all character types by default.

How can a variable be declared as an integral type directly?

Declare can declare variables directly as integral type

#!/bin/bash#declare -i sum=0forin100`;do   let sum=$sum+$Idoneecho"sum=${sum}"

Example: Say hello to every user in the system

#!/bin/bash#forin-d-f1`;do    echo"hello ${NAME}~"done

Example: Say hello to every user in the system and show their shell~

#!/bin/bash#forin-d-f1`;do    echo"hello ${NAME}~...........`cat /etc/passwd | grep ^$NAME | cut -d: -f7`"done

Example: Only the user question mark for the shell in the system is bash,

#!/bin/bash# forNAMEinch' CAT/ETC/PASSWD | Cut- D:- F1 '; DoShell_name= ' cat/etc/passwd | grep ^$NAME| Cut- D:- F7 | Sed-r' [Email protected]^/.*/(. *) @\[email protected] '`if[$SHELL _name=="Bash"]; Then        Echo "Hello ${name}~ ..... ' CAT/ETC/PASSWD | grep ^$NAME | cut-d:-f7 ' "    fi Done

Linux-based shell programming (4)-for loop