cmp

PURPOSE

     Compares two files.

SYNOPSIS
     cmp [ -l ] [ -s ] file1 file2


DESCRIPTION

     The cmp command  compares file1 and file2  and writes the
     results to standard  output.  If you specify  a - (minus)
     for file1, cmp reads  standard input.  Under default con-
     ditions, cmp displays nothing if  the files are the same.
     If they differ, cmp displays  the byte and line number at
     which the  first difference  occurs.  If  one file  is an
     initial subsequence of  the other (that is,  if cmp reads
     an end-of-file  character in one file  before finding any
     differences), cmp  notes this.  Normally, you  use cmp to
     compare non-text  files and  the diff command  to compare
     text files.

FLAGS

     -l    Displays, for  each difference, the byte  number in
           decimal and the differing bytes in octal.
     -s    Returns only an exit value.  (0 indicates identical
           files;  1 indicates  different  files; 2  indicates
           inaccessible file or a missing argument)

EXAMPLES

     1.  To determine whether two files are identical:

           cmp  prog.o.bak  prog.o

         This  compares  "prog.o.bak"  and "prog.o".   If  the
         files are identical, then a message is not displayed.
         If the files  differ, then the location  of the first
         difference is displayed.

         For instance:

           prog.o.bak  prog.o  differ:  char  5,  line  1

         If the message "cmp: EOF on prog.o.bak" is displayed,
         then  the  first part  of  "prog.o"  is identical  to
         "prog.o.bak",  but   there  is  additional   data  in
         "prog.o".
     2.  To display each pair of bytes that differ:

           cmp  -l  prog.o.bak  prog.o

         This compares  the files, and then  displays the byte
         number  (in  decimal)  and the  differing  bytes  (in
         octal)  for each  difference.   For  example, if  the
         fifth byte  is octal "101" in  "prog.o.bak" and "141"
         in "prog.o", then "cmp" displays:

                5  101  141

     3.  To compare two files without writing any messages:

           cmp  -s  prog.c.bak  prog.c

         This  gives an  exit value  of "0"  if the  files are
         identical,  "1"  if different,  or  "2"  if an  error
         occurs.  This form of the command is normally used in
         shell procedures.  For example:

           if  cmp  -s  prog.c.bak  prog.c
           then
                 echo  No  change
           fi

         This partial shell procedure  displays "No change" if
         the two files  are identical.  See page   for details
         about the if command.

RELATED INFORMATION

     The following commands:  "comm,"  "diff," and "sh."