diff(1) 						      General Commands Manual							   diff(1)

NAME

       diff - differential file and directory comparator

SYNOPSIS

       n] name] dir1 dir2

       n] name] file1 file2

       string] file1 file2

DESCRIPTION

   Comparing Directories
       If both arguments are directories, sorts the contents of the directories by name, then runs the regular file algorithm (described below) on
       text files that have the same name in each directory but are different.	Binary files that differ, common subdirectories,  and  files  that
       appear in only one directory are listed.  When comparing directories, the following options are recognized:

	      Long output format; each text file
			  is  piped  through to paginate it (see pr(1)).  Other differences are remembered and summarized after all text file dif-
			  ferences are reported.

	      Applies	  recursively to common subdirectories encountered.

	      reports files that are identical but otherwise not mentioned.

	      Starts a directory
			  in the middle of the sorted directory, beginning with file name.

   Comparing Files
       When run on regular files, and when comparing text files that differ during directory comparison, tells what lines must be changed  in  the
       files  to bring them into agreement.  usually finds a smallest sufficient set of file differences.  However, it can be misled by lines con-
       taining very few characters or by other situations.  If neither file1 nor file2 is a directory, either can be specified as  in  which  case
       the  standard input is used.  If file1 is a directory, a file in that directory whose filename is the same as the filename of file2 is used
       (and vice versa).

       There are several options for output format.  The default output format contains lines resembling the following:

       These lines resemble commands to convert file1 into file2.  The numbers after the letters pertain to file2.  In fact, by exchanging for and
       reading backwards one may ascertain equally how to convert file2 into file1.  As in 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

       Except for or which can be given with any of the others, the following options are mutually exclusive:

	      Produce a script of
		       and  commands for the editor suitable for recreating file2 from file1.  Extra commands are added to the output when compar-
		       ing directories with so that the result is a shell script for converting text files common  to  the  two  directories  from
		       their state in dir1 to their state in dir2.

	      Produce a script similar to that of the
		       option that is not useful with but is more readable by humans.

	      Produce a script similar to that of
		       but  in	the  opposite order, and with a count of changed lines on each insert or delete command.  This is the form used by
		       (see rcsdiff(1)).

	      Produce a difference list with 3 lines of context.
		       modifies the output format slightly: the output begins with identification of the files involved, followed  by  their  cre-
		       ation  dates,  then  each  change separated by a line containing about twelve asterisks Lines removed from file1 are marked
		       with and lines added to file2 are marked Lines that change from one file to the other are marked in both  files	with  with
		       Changes that lie within 3 lines of each other in the file are grouped together on output.

	      Output format similar to
		       but with n lines of context.

	      Do a fast, half-hearted job.
		       This option works only when changed stretches are short and well separated, but can be used on files of unlimited length.

	      Create a merged version of
		       file1  and  file2 on the standard output, with C preprocessor controls included so that a compilation of the result without
		       defining string is equivalent to compiling file1, while compiling the result with string defined is equivalent to compiling
		       file2.

	      Ignore trailing
		       space  characters,  except  newline  character  and treat other string of blanks as equal.  For example, and are treated as
		       equal.

	      Ignore all
		       space characters, except newline character.  For example, and are treated as equal.

	      Ignores uppercase/lowercase differences.
		       Thus is treated the same as

	      Expand tabs in output lines.
		       Normal or output adds one or more characters to the front of each line.	Resulting misalignment of indentation in the orig-
		       inal  source lines can make the output listing difficult to interpret.  This option preserves original source file indenta-
		       tion.

EXTERNAL INFLUENCES

   Environment Variables
       determines the locale to use for the locale categories when both and the corresponding environment variable (beginning with do not  specify
       a locale.  If is not set or is set to the empty string, a default of "C" (see lang(5)) is used.

       determines the space characters for the command, and the interpretation of text within file as single- and/or multi-byte characters.

       determines the language in which messages are displayed.

       If  any internationalization variable contains an invalid setting, and behave as if all internationalization variables are set to "C".  See
       environ(5).

   International Code Set Support
       Single- and multi-byte character code sets are supported with the exception that and do not recognize multi-byte alternative space  charac-
       ters.

RETURN VALUE

       Upon completion, returns with one of the following exit values:

	       0      No differences were found.

	       1      Differences were found.

	      >1      An error occurred.

EXAMPLES

       The following command creates a script file

       is added to the end of the script in order to save the file:

       The script file can then be used to create the file from the file using the editor in the following manner:

       The following command produces the difference output with 2 lines of context information before and after the line that was different:

       The following command ignores all blanks and tabs and ignores uppercase-lowercase differences.

WARNINGS

       Editing scripts produced by the or option are naive about creating lines consisting of a single dot

       When  comparing	directories  with the or options specified, first compares the files in the same manner as then runs the algorithm if they
       are not equal.  This may cause a small amount of spurious output if the files are identical  except  for  insignificant	blank  strings	or
       uppercase/lowercase differences.

       The default algorithm requires memory allocation of roughly six times the size of the file.  If sufficient memory is not available for han-
       dling large files, the option or can be used (see bdiff(1)).

       With other options if sufficient memory is not available, then either the or values can be increased.

       When run on directories with the option, recursively descends sub-trees.  When comparing deep multi-level directories, more memory  may	be
       required  than  is  currently available on the system.  The amount of memory required depends on the depth of recursion and the size of the
       files.

AUTHOR

       was developed by AT&T, the University of California, Berkeley, and HP.

FILES

       used by			     option

SEE ALSO

       bdiff(1), cmp(1), comm(1), diff3(1), diffmk(1), dircmp(1), ed(1), more(1), nroff(1), rcsdiff(1), sccsdiff(1), sdiff(1), terminfo(4).

STANDARDS CONFORMANCE

																	   diff(1)