shell编程三-循环语句

shell编程三-循环语句

for循环

for var in list
do 
   commands
done

C语言风格的for循环:

#!/bin/bash
for  (( i=1; i <= 10; i ++ ))
do
	echo value is $i
done    
#!/bin/bash
for  (( a=1, b=10; a <= 10; a++,b-- ))
do
	echo  "$a - $b"
done

while循环

while test command
do
commands
done

#!/bin/bash
var=10
while [ $var -gt 0 ]
do
	echo $var' > 0'
	var=$[ $var - 1 ]
done

until 循环

#!/bin/bash
var=10
until [ $var -lt 0 ]
do
	echo $var' > 0'
	var=$[ $var - 1 ]
done

循环其他功能

循环控制

跟其他语言一样,控制循环:
* break
* continue

循环输出

#!/bin/bash
for file in /root/*
do
	if [ -d $file ]
	then
		echo ${file}是目录
	fi
done > output.txt

示例

读取文件变量,,区分:

#!/bin/bash
input="users.csv"
while IFS=',' read -r userid name
do
  echo "adding $userid"
  useradd -c "$name" -m $userid
done < "$input”
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