Linux shell scripts use structured commands (2)

A. For command

Two. While command

Three. Until command

1.for Command Basic format

1  for inch List 2  Do 3     Commands4 done

1[Email protected]:~/testshell>CatFortest.SH 2#!/bin/Bash3#test forCommand4 5  forCityinchBeijing Shanghai Shenzhen Dalian6  Do7     EchoThe city is $city8  Done    9[Email protected]:~/testshell>./fortest.SH Ten The city is Beijing One The city is Shanghai A The city is Shenzhen -The city is Dalian

A C language-style for command

1  for ((variable assignment; condition; iterationprocess)) 2  Do 3      Commands4 done

1[Email protected]:~/testshell>CatFortest.SH 2#!/bin/Bash3#test forCommand4 5 sum=06  for((i=1; i<= -; i++ ))7  Do8((sum=sum+i))9 Ten  Done One Echo sum= $sum A  -  for((a=1, b=1;a<5,b<3; a++,b++ )) -  Do the((c = A +b)) -     Echoc =$c -  Done -[Email protected]:~/testshell>./fortest.SH  + sum=5050 -c =2 +c =4

2.while Command Basic format

1  while Test Command 2  Do 3 Other     commands4 done

1[Email protected]:~/testshell>CatWhiletest.SH 2#!/bin/Bash3#test whileCommand4 5Var=36 7  while[$var-GT0 ]8  Do9(var = var-1 ))Ten     Echovar =$var One  Done A[Email protected]:~/testshell>./whiletest.SH  -var =2 -var =1 thevar =0

3.until Command Basic format

1 until Test Commands 2  Do 3 Other     commands4 done

1[Email protected]:~/testshell>CatUntiltest.SH 2#!/bin/Bash3#testuntilCommand4 5Var=56 7 until[$var-GT8 ]8  Do9((var++ ))Ten     Echovar =$var One  Done A[Email protected]:~/testshell>./untiltest.SH  -var =6 -var =7 thevar =8 -var =9

Another thing is that the loop output can be output to the screen or output to a file, which is to add a processing command after the done command

1[Email protected]:~/testshell>CatUntiltest.SH 2#!/bin/Bash3#testuntilCommand4 5Var=56 7 until[$var-GT8 ]8  Do9((var++ ))Ten     Echovar =$var One  Done>Result.txt A[Email protected]:~/testshell>./untiltest.SH  -[Email protected]:~/testshell>ls -Untiltest.SHResult.txt the[Email protected]:~/testshell>CatResult.txt -var =6 -var =7 -var =8 +var =9

Linux shell scripts use structured commands (2)