sed search and replace help please...

mangya · 09-26-2015, 09:08 AM

Hello

I want to replace

this
<emulator>/usr/bin/qemu-kvm</emulator>

with this
<emulator>/usr/sbin/qemu-system-x86_64</emulator>

in *.xml files.

How do i do this?

I tried this.. but not working.

Code:

# sed -i "s/\<emulator\>\/usr\/bin\/qemu-kvm\<\/emulator\>/\<emulator\>\/usr\/sbin\/qemu-system-x86_64\<\/emulator\>/" *.xml

I know it can be made simple by removing <emulator> part, but for learning sake, i want to know how I can search and replace strings that contain special chars, spaces etc.

Please help. Thanks

HMW · 09-26-2015, 09:19 AM

Hi there!

Well, the easiest approach is to simply replace the chars "kvm" with "system-x86_64".

Like so:

Code:

$ echo "<emulator>/usr/bin/qemu-kvm</emulator>" | sed 's/kvm/system-x86_64/'
<emulator>/usr/bin/qemu-system-x86_64</emulator>

Best regards,
HMW

mangya · 09-26-2015, 09:28 AM

Quote:

Originally Posted by HMW

Hi there!

Well, the easiest approach is to simply replace the chars "kvm" with "system-x86_64".

Like so:

Code:

$ echo "<emulator>/usr/bin/qemu-kvm</emulator>" | sed 's/kvm/system-x86_64/'
<emulator>/usr/bin/qemu-system-x86_64</emulator>

Best regards,
HMW

Thanks for the quick reply. But you missed bin/sbin part.

I already made it working with

Code:

# sed -i "s/\/usr\/bin\/qemu-kvm/\/usr\/sbin\/qemu-system-x86_64/" *.xml

I was looking for any easy method of search and replace like bash's single quote method, so that i can avoid '\' for every special character.

Thanks

sycamorex · 09-26-2015, 09:31 AM

Quote:

Originally Posted by mangya

Hello

I want to replace

this
<emulator>/usr/bin/qemu-kvm</emulator>

with this
<emulator>/usr/sbin/qemu-system-x86_64</emulator>

in *.xml files.

How do i do this?

I tried this.. but not working.

Code:

# sed -i "s/\<emulator\>\/usr\/bin\/qemu-kvm\<\/emulator\>/\<emulator\>\/usr\/sbin\/qemu-system-x86_64\<\/emulator\>/" *.xml

I know it can be made simple by removing <emulator> part, but for learning sake, i want to know how I can search and replace strings that contain special chars, spaces etc.

Please help. Thanks

First of all, please note that you can replace / with other charactres to make it more readable (if there are forward slashes in your search string) to avoid the need to escape special characters.

Code:

sed 's@bin/qemu-kvm@sbin/qemu-system-x86_64@' *.xml

Secondly, <> are not special characters for sed so must not be escaped with \.

Code:

sed "s/\<emulator\>\/usr\/bin\/qemu-kvm\<\/emulator\>/\<emulator\>\/usr\/sbin\/qemu-system-x86_64\<\/emulator\>/" file

HMW · 09-26-2015, 09:39 AM

Quote:

Originally Posted by mangya

Thanks for the quick reply. But you missed bin/sbin part.

Hepp! Yes, you're right. Sorry about that

Glad you were able to solve it. You can shorten your sed into something like this if you want:

Code:

sed 's/bin.*kvm/sbin\/qemu-system-x86_64/'

Code:

$ echo "<emulator>/usr/bin/qemu-kvm</emulator>" | sed 's/bin.*kvm/sbin\/qemu-system-x86_64/'
<emulator>/usr/sbin/qemu-system-x86_64</emulator>

Best regards,
HMW

mangya · 09-26-2015, 09:57 AM

Thanks @sycamorex and @HMW for help.

Quote:

First of all, please note that you can replace / with other charactres to make it more readable (if there are forward slashes in your search string) to avoid the need to escape special characters.

Secondly, <> are not special characters for sed so must not be escaped with \.

Didn't know that, thanks @sycamorex.

chrism01 · 09-27-2015, 10:06 PM

You might want to have a read through the http://www.grymoire.com/Unix/Sed.html although it is a bit old.