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 NAME     
 |  |  |  | diff – differential file comparator 
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 SYNOPSIS     
 |  |  |  | diff [ −acefmnbwr ] file1 ... file2 
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 DESCRIPTION     
 |  |  |  | Diff tells what lines must be changed in two files to bring them
    into agreement. If one file is a directory, then a file in that
    directory with basename the same as that of the other file is
    used. If both files are directories, similarly named files in
    the two directories are compared by the method of diff for text
    files and cmp(1) otherwise. If more than two file
    names are given, then each argument is compared to the last argument
    as above. The −r option causes diff to process similarly named
    subdirectories recursively. When processing more than one file,
    diff prefixes file differences with a single line listing the
    two differing files, in the form of a diff command line. The −m
    flag causes this behavior even
    when processing single files. 
    
    
    The normal output contains lines of these forms: 
 These lines resemble ed commands to convert file1 into file2.
    The numbers after the letters pertain to file2. In fact, by exchanging
    ‘a’ for ‘d’ and reading backward one may ascertain equally how
    to convert file2 into file1. As in ed, identical pairs where n1
    = n2 or n3 = n4 are abbreviated as a single number. 
    
    
    Following each of these lines come all the lines that are affected
    in the first file flagged by ‘<’, then all the lines that are affected
    in the second file flagged by ‘>’. 
    
    
    The −b option causes trailing blanks (spaces and tabs) to be ignored
    and other strings of blanks to compare equal. The −w option causes
    all white-space to be removed from input lines before applying
    the difference algorithm. 
    
    
    The −n option prefixes each range with file: and inserts a space
    around the a, c, and d verbs. The −e option produces a script
    of a, c and d commands for the editor ed, which will recreate
    file2 from file1. The −f option produces a similar script, not
    useful with ed, in the opposite order. It may, however, be useful
    as input to a stream-oriented post-
    processor. 
    
    
    The −c option includes three lines of context around each change,
    merging changes whose contexts overlap. The −a flag displays the
    entire file as context. 
    
    
    Except in rare circumstances, diff finds a smallest sufficient
    set of file differences.|  |  |  | n1 a n3,n4 n1,n2 d n3
 n1,n2 c n3,n4
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 FILES     
 SOURCE     
 SEE ALSO     
 DIAGNOSTICS     
 |  |  |  | Exit status is the empty string for no differences, some for some,
    and error for trouble. 
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 BUGS     
 |  |  |  | Editing scripts produced under the −e or −f option are naive about
    creating lines consisting of a single ‘.’. 
    
    
    When running diff on directories, the notion of what is a text
    file is open to debate. 
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