Audit basename(1)

1) be stricter which number of arguments is accepted (1 or 2)
2) basename already returns a pointer to "." is argv[0] is ""
3) No need to check for *p != '/', because basename() only returns
   a string beginning with '/' which has length 1, so if strlen(p)
   == 1, the only way for suffix to be "evaluated" is for off to
   be > 0, being equal to suffix being "", but "" != "/".
4) don't calculate strlen twice for each string. Store it in a
   ssize_t and check if it's > 0.

README

@@ -9,7 +9,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
 
     UTILITY         POSIX 2008 COMPLIANT         MISSING OPTIONS
     -------         --------------------         ---------------
-=*  basename        yes                          none
+=*| basename        yes                          none
 =*  cal             yes                          none
 =*  cat             yes                          none
 =*  chgrp           yes                          none

basename.c

@@ -5,8 +5,6 @@
 
 #include "util.h"
 
-static void usage(void);
-
 void
 usage(void)
 {
@@ -16,25 +14,24 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
+	ssize_t off;
 	char *p;
-	size_t off;
 
 	ARGBEGIN {
 	default:
 		usage();
 	} ARGEND;
 
-	if (argc < 1)
+	if (argc != 1 && argc != 2)
 		usage();
 
-	p = strlen(argv[0]) ? basename(argv[0]) : ".";
-	if (argc == 2 && *p != '/') {
-		if (strlen(argv[1]) < strlen(p)) {
+	p = basename(argv[0]);
+	if (argc == 2) {
 		off = strlen(p) - strlen(argv[1]);
-			if (strcmp(&p[off], argv[1]) == 0)
+		if (off > 0 && !strcmp(p + off, argv[1]))
 			p[off] = '\0';
 	}
-	}
 	puts(p);
+
 	return 0;
 }