Question

I have a big apache configuration file and in each of the virtualhost sections, I want to add its own log entry. I am wondering if I can do it with a script.

My current configuration file is something like this;

ServerName abc.com   
some information.   
…   
……   

and I want to have it something like;

ServerName abc.com    
CustomLog "/usr/local/logs/abc.com.log"    
some information.    
…   
……       

Is it possible by some sort of script? I have lots and lots of such virtualhost entries, so manually updating is impossible.. Any ideas?

Answer 1

awk can be much simpler to use.

awk 'NR==3{print "my log"}1' INPUT_FILE

• NR is a built-in variable that tracks line numbers.
• You can also use -v and a variable name to pass values dynamically instead of hard-coding it in the script. eg. awk -v line="$var" 'NR==line{print "my log"}1' INPUT_FILE. In this case, line is an awk variable and $var can be your bash variable defined outside of awk's scope.

Test:

[jaypal:~/Temp] cat file
ServerName abc.com   
some information.   
…   
……  

[jaypal:~/Temp] awk 'NR==3{print "my log"}1' file # add log after 2 lines
ServerName abc.com   
some information.   
my log
…   
……  

[jaypal:~/Temp] awk 'NR==4{print "my log"}1' file # add log after 3 lines
ServerName abc.com   
some information.   
…   
my log
……  

[jaypal:~/Temp] var=2 # define a variable which holds the line number you want to print on
[jaypal:~/Temp] awk -v line="$var" 'NR==line{print "my log"}1' file
ServerName abc.com   
my log
some information.   
…   
……  

In the comments I saw your question of adding your log after 3 lines starting from the matched pattern (ServerName, in this example). For that you can try something like this –

awk '/ServerName/{a=NR;print;next} NR==(a+3){print$0;print "my log";next}1' file

[jaypal:~/Temp] awk '/ServerName/{a=NR;print;next} NR==(a+3){print$0;print "my log";next}1' file
ServerName abc.com   
some information.   
…   
……  
my log