shell 给文件每一行都添加指定字符串

[admin@localhost file]$ cat file
hello
hello
hello
hello
hello 

[admin@localhost file]$ cat test.sh
#!/bin/bash
while read line
do
    echo 'buy '$line
done < file >> file_b

[admin@localhost file]$ /bin/bash test.sh

[admin@localhost file]$ ls
file  file_b  test.sh

[admin@localhost file]$ cat file_b
buy hello
buy hello
buy hello
buy hello
buy hello