diffutils: Specified Lines
1.4 Suppressing Differences Whose Lines All Match a Regular Expression
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To ignore insertions and deletions of lines that match a 'grep'-style
regular expression, use the '--ignore-matching-lines=REGEXP' ('-I
REGEXP') option. You should escape regular expressions that contain
shell metacharacters to prevent the shell from expanding them. For
example, 'diff -I '^[[:digit:]]'' ignores all changes to lines beginning
with a digit.
However, '-I' only ignores the insertion or deletion of lines that
contain the regular expression if every changed line in the hunk--every
insertion and every deletion--matches the regular expression. In other
words, for each nonignorable change, 'diff' prints the complete set of
changes in its vicinity, including the ignorable ones.
You can specify more than one regular expression for lines to ignore
by using more than one '-I' option. 'diff' tries to match each line
against each regular expression.
Info Catalog
diffutils: Blank Lines
diffutils: Comparison
diffutils: Case Folding