shell-while-for

while 循环

1、基本用法：

#!/bin/bash
source /etc/profile

while read dataline
do 
  echo "$dataline"
done

2、循环读入一个文件。
方式1：

#!/bin/bash
source /etc/profile

cat $*|
while read dataline
do 
  echo "$dataline"
done

方式2：

#!/bin/bash
source /etc/profile

filename=$1
if [ ! -r "$filename" ];then
   echo "can not read $filename"
   exit 1
fi

while read dataline
do 
  echo "$dataline"
done < $filename

3、while 循环输出内容到一个文件。

#!/bin/bash
source /etc/profile

filename=$1
if [ ! -r "$filename" ];then
   echo "can not read $filename"
   exit 1
fi

while read dataline
do 
  echo "$dataline"
done < $filename >output.data

4、命令行执行for

for i in `cat num2.txt` ;do echo $i; done |awk 'BEGIN {a=0} {a+=$1} END {print a}'