Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Programming
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Databases
Mail Systems
openSolaris
Eclipse Documentation
Techotopia.com
Virtuatopia.com

How To Guides
Virtualization
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Windows
Problem Solutions
Privacy Policy

  




 

 


Node:Reversed Patches, Next:, Previous:Changed White Space, Up:Imperfect

Applying Reversed Patches

Sometimes people run diff with the new file first instead of second. This creates a diff that is "reversed". To apply such patches, give patch the -R or --reverse option. patch then attempts to swap each hunk around before applying it. Rejects come out in the swapped format.

Often patch can guess that the patch is reversed. If the first hunk of a patch fails, patch reverses the hunk to see if it can apply it that way. If it can, patch asks you if you want to have the -R option set; if it can't, patch continues to apply the patch normally. This method cannot detect a reversed patch if it is a normal diff and the first command is an append (which should have been a delete) since appends always succeed, because a null context matches anywhere. But most patches add or change lines rather than delete them, so most reversed normal diffs begin with a delete, which fails, and patch notices.

If you apply a patch that you have already applied, patch thinks it is a reversed patch and offers to un-apply the patch. This could be construed as a feature. If you did this inadvertently and you don't want to un-apply the patch, just answer n to this offer and to the subsequent "apply anyway" question--or type C-c to kill the patch process.


 
 
  Published under the terms of the GNU General Public License Design by Interspire