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DIFF(3)			    Library Functions Manual		       DIFF(3)

NAME
       diff -- generate	arbitrary sequence diffs

LIBRARY
       library "libdiff"

SYNOPSIS
       #include	<diff.h>

       int
       diff(struct diff	*p,	       int (*cmp)(const	void *,	const void *),
	   size_t size,	const void *base1,  size_t nmemb1,  const void *base2,
	   size_t nmemb2);

DESCRIPTION
       The  diff() function generates the shortest edit	script,	longest	common
       subsequence, and	edit distance going from an origin array of nmemb1 ob-
       jects, the initial member of which is pointed to	as base1; to the  tar-
       get  array  of  nmemb2  objects with initial member base2.  The size of
       each object is specified	by size.  Objects are compared by  cmp,	 which
       requires	 two arguments pointing	to the objects being compared.	It re-
       turns zero if the objects are the same, non-zero	otherwise.

       On success, diff() sets the edit	distance in p->editdist.  It allocates
       the p->ses array	of length p->sessz and fills it	with the shortest com-
       mon subsequence.	 It also allocates the p->lcs array of length p->lcssz
       and fills it with the longest common subsequence.  Both arrays must  be
       passed to free(3) by the	caller.

RETURN VALUES
       The  diff()  function returns <0	on memory allocation failure, 0	if the
       sequence	is too complicated to generate,	or >0 otherwise	on success.

EXAMPLES
       The following example takes two strings,	"asdf" and  "fdsa",  and  dis-
       plays the edit script to	go from	the first to the second.

       int cmp(const void *p1, const void *p2) {
	   return *(const char *)p1 == *(const char *)p2;
       }

       void compute(void) {
	   size_t i;
	   int rc;
	   struct diff p;

	   rc =	diff(&p, cmp, 1, "asdf", 4, "fdsa", 4);

	   if (rc < 0)
	       err(EXIT_FAILURE, NULL);
	   if (0 == rc)
	       errx(EXIT_FAILURE, "cannot compute distance");

	   for (i = 0; i < p.sessz; i++)
	       printf("%s%c\n",
		   DIFF_ADD == p.ses[i].type ?	"+" :
		   DIFF_DELETE == p.ses[i].type	?  "-" : " ",
		   *(const char	*)p.ses[i].e);
	   free(p.ses);
	   free(p.lcs);
       }

       The second example looks	for difference in words.

       int cmp(const void *p1, const void *p2) {
	   return 0 == strcmp
	       (*(const	char **)p1, *(const char **)p2);
       }

       void compute(void) {
	   size_t i;
	   int rc;
	   struct diff p;
	   const char *origin[]	= { "hello", "there" };
	   const char *target[]	= { "hello", "world" };

	   rc =	diff(&p, cmp, sizeof(char *), origin, 2, target, 2);

	   if (rc < 0)
	       err(EXIT_FAILURE, NULL);
	   if (0 == rc)
	       errx(EXIT_FAILURE, "cannot compute distance");

	   for (i = 0; i < p.sessz; i++)
	       printf("%s%s\n",
		   DIFF_ADD == p.ses[i].type ?	"+" :
		   DIFF_DELETE == p.ses[i].type	?  "-" : " ",
		   *(const char	**)p.ses[i].e);
	   free(p.ses);
	   free(p.lcs);
       }

SEE ALSO

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=diff&sektion=3&manpath=FreeBSD+Ports+15.0>

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