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(diff.info.gz) Comparison

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 What Comparison Means
 *********************
 
    There are several ways to think about the differences between two
 files.  One way to think of the differences is as a series of lines
 that were deleted from, inserted in, or changed in one file to produce
 the other file.  `diff' compares two files line by line, finds groups of
 lines that differ, and reports each group of differing lines.  It can
 report the differing lines in several formats, which have different
 purposes.
 
    GNU `diff' can show whether files are different without detailing
 the differences.  It also provides ways to suppress certain kinds of
 differences that are not important to you.  Most commonly, such
 differences are changes in the amount of white space between words or
 lines.  `diff' also provides ways to suppress differences in alphabetic
 case or in lines that match a regular expression that you provide.
 These options can accumulate; for example, you can ignore changes in
 both white space and alphabetic case.
 
    Another way to think of the differences between two files is as a
 sequence of pairs of bytes that can be either identical or different.
 `cmp' reports the differences between two files byte by byte, instead
 of line by line.  As a result, it is often more useful than `diff' for
 comparing binary files.  For text files, `cmp' is useful mainly when
 you want to know only whether two files are identical, or whether one
 file is a prefix of the other.
 
    To illustrate the effect that considering changes byte by byte can
 have compared with considering them line by line, think of what happens
 if a single newline character is added to the beginning of a file.  If
 that file is then compared with an otherwise identical file that lacks
 the newline at the beginning, `diff' will report that a blank line has
 been added to the file, while `cmp' will report that almost every byte
 of the two files differs.
 
    `diff3' normally compares three input files line by line, finds
 groups of lines that differ, and reports each group of differing lines.
 Its output is designed to make it easy to inspect two different sets of
 changes to the same file.
 

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* Hunks             Groups of differing lines.
* White Space       Suppressing differences in white space.
* Blank Lines       Suppressing differences in blank lines.
* Case Folding      Suppressing differences in alphabetic case.
* Specified Folding Suppressing differences that match regular expressions.
* Brief             Summarizing which files are different.
* Binary            Comparing binary files or forcing text comparisons.
 
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