How the shell adds content after the specified file location

Recently encountered a problem in the work, want to add a flag bit after the specified location of a file, required to be implemented in the shell script.

Problem Description:

Want to add a flag after a string of sys_config.fex text

For example, there is such a thing in Sys_config.fex

[Nand_para]

Nand_use = 1

Requires a flag = 1 to be added after [Nand_para], and finally (does not affect other content):

[Nand_para]

Flag = 1

Nand_use = 1

Specific implementation:

Reference material (http://bbs.chinaunix.net/thread-1585877-1-1.html):

Script Description:
Write "# chkconfig:2345 98 98" and "# Description:http Server" to/etc/init.d/httpd under the "#!/bin/sh" field.


I just added a parameter of-I, if not added, although the screen shows:
#!/bin/sh
# chkconfig:2345 98 98
# description:http Server

Sed-i '/#!\/bin\/sh/a\# chkconfig:2345 98 98\n# description:http server '/etc/init.d/httpd

How the shell adds content after the specified file location