Linux command: For loop

For loop:

loop operation, for Loop statement

1 . Command format:

for variable in list;

Loop body

Done

2 . Command function:

Execute Loop statement

3 . Command parameters:

for variable in list;

Loop body

Done

The list generation method for the For loop:

{N.. m}: Through curly braces, the middle is the variable traversal range, from N to m are variable traversal

' seq [ start number [step length]] end number ' SEQ 1 2 10 ' variable with a traversal value of 1 3 5 7 9 over 10 exit traversal

{1..100}

Declare-i sum=0 Declare declaring variable-I declares a variable to be an integral integer

Declare-x declaring variables as environment variables

4 . Command instance:

1, calculated from 1 to 100 and

#!/bin/bash

# program:

# calculates 1 to 100 of the and

# History Donggen 2016-10-21-20:30

Path=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bash

Export PATH

Declare-i sum=0

For I in {1..100}; Do #或者 for I in ' SEQ 1 100 '

Let sum= $SUM + $I

Done

echo "1+. +100= $SUM "

2. write a script:

1 , the value of the set variable file is/etc/passwd

2 , say hello to each user in/etc/passwd, and show each other's shell as follows:

Hello, Root, your Shell:/bin/bash

#!/bin/bash

#program:

# Say hello to the users inside/etc/passwd

#history 2016-10-21-21:30

Path=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bash

Export PATH

lines= ' Wc-l/etc/passwd | Cut-d '-f1 '

For I in ' seq 1 $LINES '; Do

echo "Helo, ' head-n $I/etc/passwd | Tail-1 | cut-d:-f1 ' Your shell is: ' Head-n $I/etc/passwd | Tail-1 | cut-d:-f7 ' "

Done

This article is from the "Learn Linux history" blog, please be sure to keep this source http://woyaoxuelinux.blog.51cto.com/5663865/1864425

Linux command: For loop