Unable to apply patch with nested directories - linux

Question

I am trying to create simple patch but file is in different directory.
My Directory structure is:
/-|hello_new.c
|-1/-|
|-2/-|
|-3/hello.c
//hello_new.c:
#include <stdio.h>
int main(int argc, char *argv[]) {
printf("Hello World\n");
}
//hello.c:
#include <stdio.h>
int main()
{
printf("Hello World\n");
}
I create the patch using:
diff -u 1/2/3/hello.c hello_new.c > hello.patch
My patch file is hello.patch:
--- 1/2/3/hello.c 2016-02-09 13:31:04.904763020 +0530
+++ hello_new.c 2016-02-08 18:35:47.299940190 +0530
## -1,6 +1,5 ##
#include <stdio.h>
-int main()
-{
+int main(int argc, char *argv[]) {
printf("Hello World\n");
}
Now I apply patch using:
patch < hello.patch
But I get patching file hello_new.c
Reversed patch detected.

Answer 1

You would solve this using the -p option of patch:
-p number
--strip=number
Set the file name strip count to number. See patch Directories.
If the before/after levels in your patch-file differ, keep in mind that patch gives precedence to the number of levels in the before part (the first line of the header). So you could do
patch -p3 < hello.patch
to avoid the reversed-patch issue for this instance.
This being GNU patch, you can preview the result by adding the --dry-run option (to avoid the nuisance of giving correct responses to the reversed-patch message):
$ patch -p3 --dry-run < hello.patch
patching file hello.c
Hunk #1 succeeded at 2 with fuzz 2 (offset 1 line).
When testing patches, e.g., if they did not match exactly (such as tab/space conversion, carriage-return line-endings), I preview patches, and may add a -l option to help patch make fewer rejects.