shell脚本按行循环读取文件内容

while IFS= read -r line
do
  length=${#line}
  if (($length<181)); then
    continue
  fi
  str1=${line:115:2}
  str2=${line:118:2}
  str3=${line:121:2}
  str4=${line:124:2}
  str6="ext data"
  str=$str4$str3$str2$str1
  str7=${line:127:24}
  printf "%s\t%s\t%s\n" "$str" "$str7" "$str6" >> ./test3.txt
  echo $str
done < ./test2.txt

"IFS="  表示将输入的行按原样传递给变量"line"，不会去掉行首行尾的空格或制表符

"read"会从读取标准输入一行并存储到"line"，使用"< ./test2.txt"重定向则会从文件一行一行读