Shell scripts 6--loops, comparing

For loop

for var in list;

Do

commands, #使用变量 $var

Done

Example

For I in {A.. Z}; do actions; Done

Latter

For ((i=0;i<10;i++))

{

Commands

}

While condition

Do

Commands

Done

Until cycle

Example

x=0;

Until [$x-eq 9];

Do

Let x + +; echo $x;

Done

If comparison statement

if contions;

Then

Commands

If

else if and ELSE statements

if condition;

Then

Commands

else if Conditon;then

Commands

Else

Commands

Fi

Simple usage:

[Condition] && action;

[Condition] | | Action

Arithmetic comparison:
[$var-eq 0]

[$var-ne 0]

Logical AND Logical OR

[$var 1-ne 0-a $var 2-gt 2]

[$var 1-ne 0-o $var 2-gt 2]

Example

　　

#!/bin/Bash#filename:compare. SH Fpath="/etc/passwd"ifthen    echofile  exits; Else    Echo does not exists; fi

Shell scripts 6--loops, comparing