How to add a line into rc.local with shell

Question

I am working on a Ubuntu 12.04 and writing a environment-auto-build shell. In the shell I need to change something in rc.local.

This is my rc.local now.

#!/bin/sh -e
#......

exit 0

I want to modify it like this:

#!/bin/sh -e
#......

nohup sh /bocommjava/socket.sh &

exit 0

Now I use nano to modify it, is there any command that can insert the line into rc.local?

Dauphin

Have you considered raising this question on askubuntu as well? – Kirschner

@wleoncio um... Good advise. but do they allow me to publish my question at two site? – Dauphin

I guess so, at least I've never had any problems doing that. ;) – Kirschner

@wleoncio I've got a good answer, but finally I decided to use crond(@reboot) to start my socket program. I've learned several ways to do it, so I think there is no need to post another question. Thank you anyway. – Dauphin

Good for you! Still, since we're on the subject, if you want to go ahead and post the question there along with the answer (you can do that in stackoverflow too), it's highly encouraged: stackoverflow.com/help/self-answer – Kirschner

Answer 1

Use Sed

For Test

sed -e '$i \nohup sh /bocommjava/socket.sh &\n' rc.local

Really Modify

sed -i -e '$i \nohup sh /bocommjava/socket.sh &\n' rc.local

Rabkin

yes, this command works. But what does $i mean? I checked many sed article, didn't found the answer. Thank u so much! – Dauphin

$i should be divide into '$' and 'i'. '$' means the last line, 'i' means insert before the current line, so '$i' means insert before the last line. – Rabkin

You might want to check if [ "`tail -n1 /etc/rc.local`" != "exit 0" ]; then ... in case someone has appended a blank line. — It wouldn't be fun to notice some weeks later that the service actually didn't restart, when the machine was rebooted – Arber

Answer 2

The easiest would be to use a scripted language (ex: python, perl, etc...).

#!/usr/bin/env python
import os

with open('/etc/rc.local') as fin:
    with open('/etc/rc.local.TMP') as fout:
        while line in fin:
            if line == 'exit 0':
                fout.write('nohup sh /bocommjava/socket.sh &\n')
            fout.write(line)

# save original version (just in case)
os.rename('/etc/rc.local', '/etc/rc.local.jic')

os.rename('/etc/rc.loca.TMP', '/etc/rc.local')

Susurration

Well, this works fine, but I still want a shell solution. Thanks a lot! – Dauphin

Quite a bit more code in basic shell. Check out bash.cyberciti.biz/file-management/read-a-file-line-by-line – Susurration

Answer 3

Find exit 0 and remove it.
Append new line with exit 0 in the end.

file=/etc/rc.local
search="exit 0"
newLine="nohup sh /bocommjava/socket.sh &"

# Remove exit 0
sudo ex -s +"g/$search/d" -cwq $file

# Find line
found=$(cat $file | grep "$newLine")

# Remove if exist
if [ "$found" != "" ]; then
    sudo ex -s +"g/$found/d" -cwq $file
fi

# Append lines
sudo echo $found >> $file
sudo echo $search >> $file

Trigraph