(diff.info.gz) Detailed If-then-else
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(diff.info.gz) Line Formats
(diff.info.gz) If-then-else
(diff.info.gz) Example If-then-else
Detailed Description of If-then-else Format
-------------------------------------------
For lines common to both files, `diff' uses the unchanged line group
format. For each hunk of differences in the merged output format, if
the hunk contains only lines from the first file, `diff' uses the old
line group format; if the hunk contains only lines from the second
file, `diff' uses the new group format; otherwise, `diff' uses the
changed group format.
The old, new, and unchanged line formats specify the output format of
lines from the first file, lines from the second file, and lines common
to both files, respectively.
The option `--ifdef=NAME' is equivalent to the following sequence of
options using shell syntax:
--old-group-format='#ifndef NAME
%<#endif /* ! NAME */
' \
--new-group-format='#ifdef NAME
%>#endif /* NAME */
' \
--unchanged-group-format='%=' \
--changed-group-format='#ifndef NAME
%<#else /* NAME */
%>#endif /* NAME */
'
You should carefully check the `diff' output for proper nesting.
For example, when using the `-D NAME' or `--ifdef=NAME' option, you
should check that if the differing lines contain any of the C
preprocessor directives `#ifdef', `#ifndef', `#else', `#elif', or
`#endif', they are nested properly and match. If they don't, you must
make corrections manually. It is a good idea to carefully check the
resulting code anyway to make sure that it really does what you want it
to; depending on how the input files were produced, the output might
contain duplicate or otherwise incorrect code.
The `patch' `-D NAME' option behaves like the `diff' `-D NAME'
option, except it operates on a file and a diff to produce a merged
file; patch Options.
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(diff.info.gz) Line Formats
(diff.info.gz) If-then-else
(diff.info.gz) Example If-then-else
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