linux 修改文件中某一行

sed -i  "1s/oldstr/newstr/" filename示例：config文件：[wusx@centos245 gather]$ cat config start=359822end=550000threads=15output=/home/wusx/gather/outputlog=/home/wusx/gather/_wget.log#将当前下的文档序列，写回config文件。sed -i "1s/start=$(($i-1))/start=$i/" /home/wusx/gather/config