Automated editing of multiple lines in a file

Curtor · 10-21-2008, 11:16 AM

I have a file that contains a multiple single lines that specify an item, and then a list under each item. I want to basically edit the file so that I can delete a list and replace it with my own list.

For example, /etc/network/interfaces:

Code:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
address 192.168.0.1
netmask 255.255.255.0
gateway 192.168.1.1

auto eth1
iface eth1 inet dhcp

iface eth2 inet dhcp
auto eth2

How would I go about setting new parameters for all the fields under eth0? My thought was to delete everything from 'auto eth0' or 'iface eth0' to, but not including, 'auto eth?' or 'iface *' or 'EOF', and then append my own configuration onto the bottom. Is there a simple way to do this, or any suggestions about how to go about it?

Yes, I know that for this example, I could just 'sudo vim /etc/network/interfaces' and edit the file, but I would like to attempt to automate the process in C eventually.

jan61 · 10-21-2008, 12:55 PM

Moin,

to delete all lines from "auto eth0" to the next blank line you can use sed:

Code:

sed '/^auto eth0$/,/^$/d' file

To edit the file in place, use the -i option:

Code:

sed -i '/^auto eth0/,/^$/d' file

Jan

chrism01 · 10-21-2008, 08:56 PM

Just FYI, Perl is very good at this sort of stuff and less fiddly than C, but similar syntax.
If you're interested, see:

http://perldoc.perl.org/
http://www.perlmonks.org/?node=Tutorials

jan61 · 10-23-2008, 04:24 PM

Moin,

Quote:

Originally Posted by chrism01

Just FYI, Perl is very good at this sort of stuff and less fiddly than C, but similar syntax.

a little bit oversized for such a simple task, isn't it? But in principle I agree with you - Perl is also my favorite to process almost every kind of files.

Jan