(diff.info.gz) Comparison
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What Comparison Means
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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.
Menu
* 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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