Linux – Edit a file via bash script

bashcentoslinux

I am a beginner in bash scripting.I want to create a bash script to install install and configure stuffs on my linux box in an automated way.

Suppose i want to edit 

/etc/yum.repos.d/epel.repo

by the bash script

What i want to do is as follows

  1. Open file /etc/yum.repos.d/epel.repo
  2. Find [epel] section
  3. Add a line priority=10 just after line enabled=1 in the epel section

For the first part i added

yum install nano
nano /etc/yum.repos.d/epel.repo

My Question is how to do the 2 and 3rd part with bash script using nano (if possible , in case not possible then show me with sed)

Also at some points i will have to modify variables in files
For e.g

  1. enable = 0 to enable = 1
  2. Testing = "1" to Testing = "0"
  3. Add text in a line . functions = to function = "text1","text2"
  4. Add some text to a file and save it(with nano)

I know its demanding but i need to create this for a friend who is noob at server management.Unfortunately i don't have time to study bash scripting from start as my exams as near.I will use your examples to write the script.

Guys thanks for all the replies
I have successfully done most of the bash script

However i have another problem
Lets suppose i want to modify nginx.conf using sed
We will deal with worker_processes
Now i want use sed to do the following
1.Find the FIRST occurrence of worker_processes in that conf and replace text with worker_processes 4;

Special Note Here: This is just an example. It may happen that the conf contain
worker_processes 1; . This is hard part . I want a sed command that find the FIRST wHOLE match case of the word worker_processes , delete line of text where the word is found and and paste worker_processes 4; there and then save file.
This is the most reliable method i though of when editing files (without nay risk of breaking any conf

One last suggestion
I used
sed -i 's/enabled=0/enabled=1/g' /etc/yum.repos.d/remi.repo
to change enabled =0 to enabled=1 under the [remi] section in remi.repo .However i have a feeling that it may modify all enabled=0 in that file , which will wreak the server.Can anyone suggest a better code.

Another stuff i am not sure of:P
I want to edit a file that has this as Text
Testing = "0"(Yes it has quotes and i need to keep it)
It should be modified from
Testing = "0" to Testing = "1"(with quotes)

Also i need to add some text with quotes at the end of a file with sed
Like "Thanks Quanta"(with quote)
For php you put a \ with echoing quotes , don't know how it is done for bash

Another thing
I need to modify a line in a conf but i don't remember what is the whole of text to replaced

Like its listen = something; , i want to modify it to listen = /tmp/php5-fpm.sock;

Big thumbs up for up quanta

Thanks for the awesome support guys

Best Answer

sed '/enabled=1/a\priority=10' /etc/yum.repos.d/epel.repo

Specify an in-place editing option (-i) if you want (makes the backup with .bak extension first):

sed -i.bak '/enabled=1/a\priority=10' /etc/yum.repos.d/epel.repo

Now i want use sed to do the following 1.Find the FIRST occurrence of worker_processes in that conf and replace text with worker_processes 4;

sed '0,/worker_processes [0-9]*;/s//worker_processes 4;/' /etc/nginx/nginx.conf

One last suggestion I used sed -i 's/enabled=0/enabled=1/g' /etc/yum.repos.d/remi.repo to change enabled=0 to enabled=1 under the [remi] section in remi.repo. However i have a feeling that it may modify all enabled=0 in that file , which will wreak the server.Can anyone suggest a better code

Here for you:

sed '/\[remi\]/,/enabled=0/ { s/enabled=0/enabled=1/ }' remi.repo

Another stuff i am not sure of:P I want to edit a file that has this as Text Testing = "0"(Yes it has quotes and i need to keep it) It should be modified from Testing = "0" to Testing = "1"(with quotes)

sed 's/Testing = "0"/Testing = "1"/g'

Also i need to add some text with quotes at the end of a file with sed Like "Thanks Quanta"(with quote) For php you put a \ with echoing quotes , don't know how it is done for bash

sed '$a"Werulz, you are welcome"\'

Another thing I need to modify a line in a conf but i don't remember what is the whole of text to replaced

Like its listen = something; , i want to modify it to listen = /tmp/php5-fpm.sock;

sed 's/listen = .*/listen = \/tmp\/php5-fpm.sock;/'
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