The lines of text in some of the diff
output formats are
preceded by one or two characters that indicate whether the text is
inserted, deleted, or changed. The addition of those characters can
cause tabs to move to the next tab stop, throwing off the alignment of
columns in the line. GNU diff
provides two ways
to make tab-aligned columns line up correctly.
The first way is to have diff
convert all tabs into the correct
number of spaces before outputting them; select this method with the
--expand-tabs (-t) option. To use this form of output with
patch
, you must give patch
the -l or
--ignore-white-space option (see Applying Patches with Changed White Space, for more
information). diff
normally assumes that tab stops are set
every 8 print columns, but this can be altered by the
--tabsize=columns option.
The other method for making tabs line up correctly is to add a tab character instead of a space after the indicator character at the beginning of the line. This ensures that all following tab characters are in the same position relative to tab stops that they were in the original files, so that the output is aligned correctly. Its disadvantage is that it can make long lines too long to fit on one line of the screen or the paper. It also does not work with the unified output format, which does not have a space character after the change type indicator character. Select this method with the -T or --initial-tab option.