This section describes variables that specify the programs to be used for applying patches and for computing the main difference regions (not the fine difference regions):
These variables specify the programs to use to produce differences and do patching.
These variables specify the options to pass to the above utilities.
ediff-diff-options, it may be useful to specify options
such as ‘-w’ that ignore certain kinds of changes. However,
Ediff does not let you use the option ‘-c’, as it doesn’t recognize this
This variable specifies the coding system to use when reading the output
that the programs
diff send to Emacs. The default
raw-text, and this should work fine in Unix and in most
cases under Windows NT/95/98/2000. There are
for which the default option doesn’t work under Windows. In such cases,
raw-text-dos might work. If not, you will have to experiment with
other coding systems or use GNU diff.
The program to use to apply patches. Since there are certain
incompatibilities between the different versions of the patch program, the
best way to stay out of trouble is to use a GNU-compatible version.
Otherwise, you may have to tune the values of the variables
ediff-backup-extension as described below.
Options to pass to
Note: the ‘-b’ and ‘-z’ options should be specified in
‘ediff-backup-specs’, not in
It is recommended to pass the ‘-f’ option to the patch program, so it won’t ask questions. However, some implementations don’t accept this option, in which case the default value of this variable should be changed.
Backup extension used by the patch program. Must be specified, even if
ediff-backup-specs is given.
Backup directives to pass to the patch program. Ediff requires that the old version of the file (before applying the patch) is saved in a file named the-patch-file.extension. Usually ‘extension’ is ‘.orig’, but this can be changed by the user, and may also be system-dependent. Therefore, Ediff needs to know the backup extension used by the patch program.
Some versions of the patch program let the user specify ‘-b backup-extension’. Other versions only permit ‘-b’, which (usually) assumes the extension ‘.orig’. Yet others force you to use ‘-z<backup-extension>’.
Note that both ‘ediff-backup-extension’ and ‘ediff-backup-specs’ must be properly set. If your patch program takes the option ‘-b’, but not ‘-b extension’, the variable ‘ediff-backup-extension’ must still be set so Ediff will know which extension to use.
Because Ediff limits the options you may want to pass to the
program, it partially makes up for this drawback by letting you save the
diff in your preferred format, which is specified via
the above two variables.
The output generated by
ediff-custom-diff-program (which doesn’t
even have to be a standard-style
diff!) is not used by Ediff. It is
provided exclusively so that you can
it later, send it over email, etc. For instance, after reviewing the
differences, you may want to send context differences to a colleague.
Since Ediff ignores the ‘-c’ option in
ediff-diff-program, you would have to run
diff -c separately
just to produce the list of differences. Fortunately,
eliminate this nuisance by keeping a copy of a difference list in the
desired format in a buffer that can be displayed via the command D.
Specifies the default directory to look for patches.
Warning: Ediff does not support the output format of VMS
diff. Instead, make sure you are using some implementation of POSIX
diff, such as