xref: /openbsd/usr.bin/less/filename.c (revision 8529ddd3)
1 /*
2  * Copyright (C) 1984-2012  Mark Nudelman
3  *
4  * You may distribute under the terms of either the GNU General Public
5  * License or the Less License, as specified in the README file.
6  *
7  * For more information, see the README file.
8  */
9 
10 
11 /*
12  * Routines to mess around with filenames (and files).
13  * Much of this is very OS dependent.
14  */
15 
16 #include "less.h"
17 #include "lglob.h"
18 #if MSDOS_COMPILER
19 #include <dos.h>
20 #if MSDOS_COMPILER==WIN32C && !defined(_MSC_VER)
21 #include <dir.h>
22 #endif
23 #if MSDOS_COMPILER==DJGPPC
24 #include <glob.h>
25 #include <dir.h>
26 #define _MAX_PATH	PATH_MAX
27 #endif
28 #endif
29 #ifdef _OSK
30 #include <rbf.h>
31 #ifndef _OSK_MWC32
32 #include <modes.h>
33 #endif
34 #endif
35 #if OS2
36 #include <signal.h>
37 #endif
38 
39 #if HAVE_STAT
40 #include <sys/stat.h>
41 #ifndef S_ISDIR
42 #define	S_ISDIR(m)	(((m) & S_IFMT) == S_IFDIR)
43 #endif
44 #ifndef S_ISREG
45 #define	S_ISREG(m)	(((m) & S_IFMT) == S_IFREG)
46 #endif
47 #endif
48 
49 
50 extern int force_open;
51 extern int secure;
52 extern int use_lessopen;
53 extern int ctldisp;
54 extern int utf_mode;
55 extern IFILE curr_ifile;
56 extern IFILE old_ifile;
57 #if SPACES_IN_FILENAMES
58 extern char openquote;
59 extern char closequote;
60 #endif
61 
62 /*
63  * Remove quotes around a filename.
64  */
65 	public char *
66 shell_unquote(str)
67 	char *str;
68 {
69 	char *name;
70 	char *p;
71 
72 	name = p = (char *) ecalloc(strlen(str)+1, sizeof(char));
73 	if (*str == openquote)
74 	{
75 		str++;
76 		while (*str != '\0')
77 		{
78 			if (*str == closequote)
79 			{
80 				if (str[1] != closequote)
81 					break;
82 				str++;
83 			}
84 			*p++ = *str++;
85 		}
86 	} else
87 	{
88 		char *esc = get_meta_escape();
89 		int esclen = strlen(esc);
90 		while (*str != '\0')
91 		{
92 			if (esclen > 0 && strncmp(str, esc, esclen) == 0)
93 				str += esclen;
94 			*p++ = *str++;
95 		}
96 	}
97 	*p = '\0';
98 	return (name);
99 }
100 
101 /*
102  * Get the shell's escape character.
103  */
104 	public char *
105 get_meta_escape()
106 {
107 	char *s;
108 
109 	s = lgetenv("LESSMETAESCAPE");
110 	if (s == NULL)
111 		s = DEF_METAESCAPE;
112 	return (s);
113 }
114 
115 /*
116  * Get the characters which the shell considers to be "metacharacters".
117  */
118 	static char *
119 metachars()
120 {
121 	static char *mchars = NULL;
122 
123 	if (mchars == NULL)
124 	{
125 		mchars = lgetenv("LESSMETACHARS");
126 		if (mchars == NULL)
127 			mchars = DEF_METACHARS;
128 	}
129 	return (mchars);
130 }
131 
132 /*
133  * Is this a shell metacharacter?
134  */
135 	static int
136 metachar(c)
137 	char c;
138 {
139 	return (strchr(metachars(), c) != NULL);
140 }
141 
142 /*
143  * Insert a backslash before each metacharacter in a string.
144  */
145 	public char *
146 shell_quote(s)
147 	char *s;
148 {
149 	char *p;
150 	char *newstr;
151 	int len;
152 	char *esc = get_meta_escape();
153 	int esclen = strlen(esc);
154 	int use_quotes = 0;
155 	int have_quotes = 0;
156 
157 	/*
158 	 * Determine how big a string we need to allocate.
159 	 */
160 	len = 1; /* Trailing null byte */
161 	for (p = s;  *p != '\0';  p++)
162 	{
163 		len++;
164 		if (*p == openquote || *p == closequote)
165 			have_quotes = 1;
166 		if (metachar(*p))
167 		{
168 			if (esclen == 0)
169 			{
170 				/*
171 				 * We've got a metachar, but this shell
172 				 * doesn't support escape chars.  Use quotes.
173 				 */
174 				use_quotes = 1;
175 			} else
176 			{
177 				/*
178 				 * Allow space for the escape char.
179 				 */
180 				len += esclen;
181 			}
182 		}
183 	}
184 	if (use_quotes)
185 	{
186 		if (have_quotes)
187 			/*
188 			 * We can't quote a string that contains quotes.
189 			 */
190 			return (NULL);
191 		len = strlen(s) + 3;
192 	}
193 	/*
194 	 * Allocate and construct the new string.
195 	 */
196 	newstr = p = (char *) ecalloc(len, sizeof(char));
197 	if (use_quotes)
198 	{
199 		SNPRINTF3(newstr, len, "%c%s%c", openquote, s, closequote);
200 	} else
201 	{
202 		while (*s != '\0')
203 		{
204 			if (metachar(*s))
205 			{
206 				/*
207 				 * Add the escape char.
208 				 */
209 				strlcpy(p, esc, newstr + len - p);
210 				p += esclen;
211 			}
212 			*p++ = *s++;
213 		}
214 		*p = '\0';
215 	}
216 	return (newstr);
217 }
218 
219 /*
220  * Return a pathname that points to a specified file in a specified directory.
221  * Return NULL if the file does not exist in the directory.
222  */
223 	static char *
224 dirfile(dirname, filename)
225 	char *dirname;
226 	char *filename;
227 {
228 	char *pathname;
229 	char *qpathname;
230 	size_t len;
231 	int f;
232 
233 	if (dirname == NULL || *dirname == '\0')
234 		return (NULL);
235 	/*
236 	 * Construct the full pathname.
237 	 */
238 	len= strlen(dirname) + strlen(filename) + 2;
239 	pathname = (char *) calloc(len, sizeof(char));
240 	if (pathname == NULL)
241 		return (NULL);
242 	SNPRINTF3(pathname, len, "%s%s%s", dirname, PATHNAME_SEP, filename);
243 	/*
244 	 * Make sure the file exists.
245 	 */
246 	qpathname = shell_unquote(pathname);
247 	f = open(qpathname, OPEN_READ);
248 	if (f < 0)
249 	{
250 		free(pathname);
251 		pathname = NULL;
252 	} else
253 	{
254 		close(f);
255 	}
256 	free(qpathname);
257 	return (pathname);
258 }
259 
260 #if USERFILE
261 /*
262  * Return the full pathname of the given file in the "home directory".
263  */
264 	public char *
265 homefile(filename)
266 	char *filename;
267 {
268 	register char *pathname;
269 
270 	/*
271 	 * Try $HOME/filename.
272 	 */
273 	pathname = dirfile(lgetenv("HOME"), filename);
274 	if (pathname != NULL)
275 		return (pathname);
276 #if OS2
277 	/*
278 	 * Try $INIT/filename.
279 	 */
280 	pathname = dirfile(lgetenv("INIT"), filename);
281 	if (pathname != NULL)
282 		return (pathname);
283 #endif
284 #if MSDOS_COMPILER || OS2
285 	/*
286 	 * Look for the file anywhere on search path.
287 	 */
288 	pathname = (char *) calloc(_MAX_PATH, sizeof(char));
289 #if MSDOS_COMPILER==DJGPPC
290 	{
291 		char *res = searchpath(filename);
292 		if (res == 0)
293 			*pathname = '\0';
294 		else
295 			strlcpy(pathname, res, _MAX_PATH);
296 	}
297 #else
298 	_searchenv(filename, "PATH", pathname);
299 #endif
300 	if (*pathname != '\0')
301 		return (pathname);
302 	free(pathname);
303 #endif
304 	return (NULL);
305 }
306 #endif /* USERFILE */
307 
308 /*
309  * Expand a string, substituting any "%" with the current filename,
310  * and any "#" with the previous filename.
311  * But a string of N "%"s is just replaced with N-1 "%"s.
312  * Likewise for a string of N "#"s.
313  * {{ This is a lot of work just to support % and #. }}
314  */
315 	public char *
316 fexpand(s)
317 	char *s;
318 {
319 	register char *fr, *to;
320 	register int n;
321 	register char *e;
322 	IFILE ifile;
323 
324 #define	fchar_ifile(c) \
325 	((c) == '%' ? curr_ifile : \
326 	 (c) == '#' ? old_ifile : NULL_IFILE)
327 
328 	/*
329 	 * Make one pass to see how big a buffer we
330 	 * need to allocate for the expanded string.
331 	 */
332 	n = 0;
333 	for (fr = s;  *fr != '\0';  fr++)
334 	{
335 		switch (*fr)
336 		{
337 		case '%':
338 		case '#':
339 			if (fr > s && fr[-1] == *fr)
340 			{
341 				/*
342 				 * Second (or later) char in a string
343 				 * of identical chars.  Treat as normal.
344 				 */
345 				n++;
346 			} else if (fr[1] != *fr)
347 			{
348 				/*
349 				 * Single char (not repeated).  Treat specially.
350 				 */
351 				ifile = fchar_ifile(*fr);
352 				if (ifile == NULL_IFILE)
353 					n++;
354 				else
355 					n += strlen(get_filename(ifile));
356 			}
357 			/*
358 			 * Else it is the first char in a string of
359 			 * identical chars.  Just discard it.
360 			 */
361 			break;
362 		default:
363 			n++;
364 			break;
365 		}
366 	}
367 
368 	e = (char *) ecalloc(n+1, sizeof(char));
369 
370 	/*
371 	 * Now copy the string, expanding any "%" or "#".
372 	 */
373 	to = e;
374 	for (fr = s;  *fr != '\0';  fr++)
375 	{
376 		switch (*fr)
377 		{
378 		case '%':
379 		case '#':
380 			if (fr > s && fr[-1] == *fr)
381 			{
382 				*to++ = *fr;
383 			} else if (fr[1] != *fr)
384 			{
385 				ifile = fchar_ifile(*fr);
386 				if (ifile == NULL_IFILE)
387 					*to++ = *fr;
388 				else
389 				{
390 					strlcpy(to, get_filename(ifile),
391 					    e + n + 1 - to);
392 					to += strlen(to);
393 				}
394 			}
395 			break;
396 		default:
397 			*to++ = *fr;
398 			break;
399 		}
400 	}
401 	*to = '\0';
402 	return (e);
403 }
404 
405 
406 #if TAB_COMPLETE_FILENAME
407 
408 /*
409  * Return a blank-separated list of filenames which "complete"
410  * the given string.
411  */
412 	public char *
413 fcomplete(s)
414 	char *s;
415 {
416 	char *fpat;
417 	char *qs;
418 	size_t len;
419 
420 	if (secure)
421 		return (NULL);
422 	/*
423 	 * Complete the filename "s" by globbing "s*".
424 	 */
425 #if MSDOS_COMPILER && (MSDOS_COMPILER == MSOFTC || MSDOS_COMPILER == BORLANDC)
426 	/*
427 	 * But in DOS, we have to glob "s*.*".
428 	 * But if the final component of the filename already has
429 	 * a dot in it, just do "s*".
430 	 * (Thus, "FILE" is globbed as "FILE*.*",
431 	 *  but "FILE.A" is globbed as "FILE.A*").
432 	 */
433 	{
434 		char *slash;
435 		for (slash = s+strlen(s)-1;  slash > s;  slash--)
436 			if (*slash == *PATHNAME_SEP || *slash == '/')
437 				break;
438 		len = strlen(s) + 4;
439 		fpat = (char *) ecalloc(len, sizeof(char));
440 		if (strchr(slash, '.') == NULL)
441 			SNPRINTF1(fpat, len, "%s*.*", s);
442 		else
443 			SNPRINTF1(fpat, len, "%s*", s);
444 	}
445 #else
446 	{
447 	len = strlen(s) + 2;
448 	fpat = (char *) ecalloc(len, sizeof(char));
449 	SNPRINTF1(fpat, len, "%s*", s);
450 	}
451 #endif
452 	qs = lglob(fpat);
453 	s = shell_unquote(qs);
454 	if (strcmp(s,fpat) == 0)
455 	{
456 		/*
457 		 * The filename didn't expand.
458 		 */
459 		free(qs);
460 		qs = NULL;
461 	}
462 	free(s);
463 	free(fpat);
464 	return (qs);
465 }
466 #endif
467 
468 /*
469  * Try to determine if a file is "binary".
470  * This is just a guess, and we need not try too hard to make it accurate.
471  */
472 	public int
473 bin_file(f)
474 	int f;
475 {
476 	int n;
477 	int bin_count = 0;
478 	char data[256];
479 	char* p;
480 	char* pend;
481 
482 	if (!seekable(f))
483 		return (0);
484 	if (lseek(f, (off_t)0, SEEK_SET) == BAD_LSEEK)
485 		return (0);
486 	n = read(f, data, sizeof(data));
487 	pend = &data[n];
488 	for (p = data;  p < pend;  )
489 	{
490 		LWCHAR c = step_char(&p, +1, pend);
491 		if (ctldisp == OPT_ONPLUS && IS_CSI_START(c))
492 		{
493 			do {
494 				c = step_char(&p, +1, pend);
495 			} while (p < pend && is_ansi_middle(c));
496 		} else if (binary_char(c))
497 			bin_count++;
498 	}
499 	/*
500 	 * Call it a binary file if there are more than 5 binary characters
501 	 * in the first 256 bytes of the file.
502 	 */
503 	return (bin_count > 5);
504 }
505 
506 /*
507  * Try to determine the size of a file by seeking to the end.
508  */
509 	static POSITION
510 seek_filesize(f)
511 	int f;
512 {
513 	off_t spos;
514 
515 	spos = lseek(f, (off_t)0, SEEK_END);
516 	if (spos == BAD_LSEEK)
517 		return (NULL_POSITION);
518 	return ((POSITION) spos);
519 }
520 
521 /*
522  * Read a string from a file.
523  * Return a pointer to the string in memory.
524  */
525 	static char *
526 readfd(fd)
527 	FILE *fd;
528 {
529 	int len;
530 	int ch;
531 	char *buf;
532 	char *p;
533 
534 	/*
535 	 * Make a guess about how many chars in the string
536 	 * and allocate a buffer to hold it.
537 	 */
538 	len = 100;
539 	buf = (char *) ecalloc(len, sizeof(char));
540 	for (p = buf;  ;  p++)
541 	{
542 		if ((ch = getc(fd)) == '\n' || ch == EOF)
543 			break;
544 		if (p - buf >= len-1)
545 		{
546 			/*
547 			 * The string is too big to fit in the buffer we have.
548 			 * Allocate a new buffer, twice as big.
549 			 */
550 			len *= 2;
551 			*p = '\0';
552 			p = (char *) ecalloc(len, sizeof(char));
553 			strlcpy(p, buf, len);
554 			free(buf);
555 			buf = p;
556 			p = buf + strlen(buf);
557 		}
558 		*p = ch;
559 	}
560 	*p = '\0';
561 	return (buf);
562 }
563 
564 
565 
566 #if HAVE_POPEN
567 
568 FILE *popen();
569 
570 /*
571  * Execute a shell command.
572  * Return a pointer to a pipe connected to the shell command's standard output.
573  */
574 	static FILE *
575 shellcmd(cmd)
576 	char *cmd;
577 {
578 	FILE *fd;
579 
580 #if HAVE_SHELL
581 	char *shell;
582 
583 	shell = lgetenv("SHELL");
584 	if (shell != NULL && *shell != '\0')
585 	{
586 		char *scmd;
587 		char *esccmd;
588 
589 		/*
590 		 * Read the output of <$SHELL -c cmd>.
591 		 * Escape any metacharacters in the command.
592 		 */
593 		esccmd = shell_quote(cmd);
594 		if (esccmd == NULL)
595 		{
596 			fd = popen(cmd, "r");
597 		} else
598 		{
599 			size_t len = strlen(shell) + strlen(esccmd) + 5;
600 			scmd = (char *) ecalloc(len, sizeof(char));
601 			SNPRINTF3(scmd, len, "%s %s %s", shell, shell_coption(), esccmd);
602 			free(esccmd);
603 			fd = popen(scmd, "r");
604 			free(scmd);
605 		}
606 	} else
607 #endif
608 	{
609 		fd = popen(cmd, "r");
610 	}
611 	/*
612 	 * Redirection in `popen' might have messed with the
613 	 * standard devices.  Restore binary input mode.
614 	 */
615 	SET_BINARY(0);
616 	return (fd);
617 }
618 
619 #endif /* HAVE_POPEN */
620 
621 
622 #if !SMALL
623 /*
624  * Expand a filename, doing any system-specific metacharacter substitutions.
625  */
626 	public char *
627 lglob(filename)
628 	char *filename;
629 {
630 	char *gfilename;
631 	char *ofilename;
632 
633 	ofilename = fexpand(filename);
634 	if (secure)
635 		return (ofilename);
636 	filename = shell_unquote(ofilename);
637 
638 #ifdef DECL_GLOB_LIST
639 {
640 	/*
641 	 * The globbing function returns a list of names.
642 	 */
643 	int length;
644 	char *p;
645 	char *qfilename;
646 	DECL_GLOB_LIST(list)
647 
648 	GLOB_LIST(filename, list);
649 	if (GLOB_LIST_FAILED(list))
650 	{
651 		free(filename);
652 		return (ofilename);
653 	}
654 	length = 1; /* Room for trailing null byte */
655 	for (SCAN_GLOB_LIST(list, p))
656 	{
657 		INIT_GLOB_LIST(list, p);
658 		qfilename = shell_quote(p);
659 		if (qfilename != NULL)
660 		{
661 	  		length += strlen(qfilename) + 1;
662 			free(qfilename);
663 		}
664 	}
665 	gfilename = (char *) ecalloc(length, sizeof(char));
666 	for (SCAN_GLOB_LIST(list, p))
667 	{
668 		INIT_GLOB_LIST(list, p);
669 		qfilename = shell_quote(p);
670 		if (qfilename != NULL)
671 		{
672 			snprintf(gfilename + strlen(gfilename),
673 			    length - strlen(gfilename), "%s ", qfilename);
674 			free(qfilename);
675 		}
676 	}
677 	/*
678 	 * Overwrite the final trailing space with a null terminator.
679 	 */
680 	if (gfilename[0] != '\0' && gfilename[strlen(gfilename) - 1] == ' ')
681 		gfilename[strlen(gfilename) - 1] = '\0';
682 	GLOB_LIST_DONE(list);
683 }
684 #else
685 #ifdef DECL_GLOB_NAME
686 {
687 	/*
688 	 * The globbing function returns a single name, and
689 	 * is called multiple times to walk thru all names.
690 	 */
691 	register char *p;
692 	register int len;
693 	register int n;
694 	char *pathname;
695 	char *qpathname;
696 	DECL_GLOB_NAME(fnd,drive,dir,fname,ext,handle)
697 
698 	GLOB_FIRST_NAME(filename, &fnd, handle);
699 	if (GLOB_FIRST_FAILED(handle))
700 	{
701 		free(filename);
702 		return (ofilename);
703 	}
704 
705 	_splitpath(filename, drive, dir, fname, ext);
706 	len = 100;
707 	gfilename = (char *) ecalloc(len, sizeof(char));
708 	p = gfilename;
709 	do {
710 		n = strlen(drive) + strlen(dir) + strlen(fnd.GLOB_NAME) + 1;
711 		pathname = (char *) ecalloc(n, sizeof(char));
712 		SNPRINTF3(pathname, n, "%s%s%s", drive, dir, fnd.GLOB_NAME);
713 		qpathname = shell_quote(pathname);
714 		free(pathname);
715 		if (qpathname != NULL)
716 		{
717 			n = strlen(qpathname);
718 			while (p - gfilename + n + 2 >= len)
719 			{
720 				/*
721 				 * No room in current buffer.
722 				 * Allocate a bigger one.
723 				 */
724 				len *= 2;
725 				*p = '\0';
726 				p = (char *) ecalloc(len, sizeof(char));
727 				strlcpy(p, gfilename, len);
728 				free(gfilename);
729 				gfilename = p;
730 				p = gfilename + strlen(gfilename);
731 			}
732 			strlcpy(p, qpathname, gfilename + len - p);
733 			free(qpathname);
734 			p += n;
735 			*p++ = ' ';
736 		}
737 	} while (GLOB_NEXT_NAME(handle, &fnd) == 0);
738 
739 	/*
740 	 * Overwrite the final trailing space with a null terminator.
741 	 */
742 	*--p = '\0';
743 	GLOB_NAME_DONE(handle);
744 }
745 #else
746 #if HAVE_POPEN
747 {
748 	/*
749 	 * We get the shell to glob the filename for us by passing
750 	 * an "echo" command to the shell and reading its output.
751 	 */
752 	FILE *fd;
753 	char *s;
754 	char *lessecho;
755 	char *cmd;
756 	char *esc;
757 	size_t len;
758 
759 	esc = get_meta_escape();
760 	if (strlen(esc) == 0)
761 		esc = "-";
762 	esc = shell_quote(esc);
763 	if (esc == NULL)
764 	{
765 		free(filename);
766 		return (ofilename);
767 	}
768 	lessecho = lgetenv("LESSECHO");
769 	if (lessecho == NULL || *lessecho == '\0')
770 		lessecho = "lessecho";
771 	/*
772 	 * Invoke lessecho, and read its output (a globbed list of filenames).
773 	 */
774 	len = strlen(lessecho) + strlen(ofilename) + (7*strlen(metachars())) + 24;
775 	cmd = (char *) ecalloc(len, sizeof(char));
776 	SNPRINTF4(cmd, len, "%s -p0x%x -d0x%x -e%s ", lessecho, openquote, closequote, esc);
777 	free(esc);
778 	for (s = metachars();  *s != '\0';  s++)
779 		snprintf(cmd + strlen(cmd), len - strlen(cmd), "-n0x%x ", *s);
780 	snprintf(cmd + strlen(cmd), len - strlen(cmd), "-- %s", ofilename);
781 	fd = shellcmd(cmd);
782 	free(cmd);
783 	if (fd == NULL)
784 	{
785 		/*
786 		 * Cannot create the pipe.
787 		 * Just return the original (fexpanded) filename.
788 		 */
789 		free(filename);
790 		return (ofilename);
791 	}
792 	gfilename = readfd(fd);
793 	pclose(fd);
794 	if (*gfilename == '\0')
795 	{
796 		free(gfilename);
797 		free(filename);
798 		return (ofilename);
799 	}
800 }
801 #else
802 	/*
803 	 * No globbing functions at all.  Just use the fexpanded filename.
804 	 */
805 	gfilename = save(filename);
806 #endif
807 #endif
808 #endif
809 	free(filename);
810 	free(ofilename);
811 	return (gfilename);
812 }
813 #endif /* !SMALL */
814 
815 /*
816  * Return number of %s escapes in a string.
817  * Return a large number if there are any other % escapes besides %s.
818  */
819 	static int
820 num_pct_s(lessopen)
821 	char *lessopen;
822 {
823 	int num;
824 
825 	for (num = 0;; num++)
826 	{
827 		lessopen = strchr(lessopen, '%');
828 		if (lessopen == NULL)
829 			break;
830 		if (*++lessopen != 's')
831 			return (999);
832 	}
833 	return (num);
834 }
835 
836 /*
837  * See if we should open a "replacement file"
838  * instead of the file we're about to open.
839  */
840 	public char *
841 open_altfile(filename, pf, pfd)
842 	char *filename;
843 	int *pf;
844 	void **pfd;
845 {
846 #if !HAVE_POPEN
847 	return (NULL);
848 #else
849 	char *lessopen;
850 	char *cmd;
851 	size_t len;
852 	FILE *fd;
853 #if HAVE_FILENO
854 	int returnfd = 0;
855 #endif
856 
857 	if (!use_lessopen || secure)
858 		return (NULL);
859 	ch_ungetchar(-1);
860 	if ((lessopen = lgetenv("LESSOPEN")) == NULL)
861 		return (NULL);
862 	while (*lessopen == '|')
863 	{
864 		/*
865 		 * If LESSOPEN starts with a |, it indicates
866 		 * a "pipe preprocessor".
867 		 */
868 #if !HAVE_FILENO
869 		error("LESSOPEN pipe is not supported", NULL_PARG);
870 		return (NULL);
871 #else
872 		lessopen++;
873 		returnfd++;
874 #endif
875 	}
876 	if (*lessopen == '-') {
877 		/*
878 		 * Lessopen preprocessor will accept "-" as a filename.
879 		 */
880 		lessopen++;
881 	} else {
882 		if (strcmp(filename, "-") == 0)
883 			return (NULL);
884 	}
885 	if (num_pct_s(lessopen) > 1)
886 	{
887 		error("Invalid LESSOPEN variable", NULL_PARG);
888 		return (NULL);
889 	}
890 
891 	len = strlen(lessopen) + strlen(filename) + 2;
892 	cmd = (char *) ecalloc(len, sizeof(char));
893 	SNPRINTF1(cmd, len, lessopen, filename);
894 	fd = shellcmd(cmd);
895 	free(cmd);
896 	if (fd == NULL)
897 	{
898 		/*
899 		 * Cannot create the pipe.
900 		 */
901 		return (NULL);
902 	}
903 #if HAVE_FILENO
904 	if (returnfd)
905 	{
906 		int f;
907 		char c;
908 
909 		/*
910 		 * Read one char to see if the pipe will produce any data.
911 		 * If it does, push the char back on the pipe.
912 		 */
913 		f = fileno(fd);
914 		SET_BINARY(f);
915 		if (read(f, &c, 1) != 1)
916 		{
917 			/*
918 			 * Pipe is empty.
919 			 * If more than 1 pipe char was specified,
920 			 * the exit status tells whether the file itself
921 			 * is empty, or if there is no alt file.
922 			 * If only one pipe char, just assume no alt file.
923 			 */
924 			int status = pclose(fd);
925 			if (returnfd > 1 && status == 0) {
926 				*pfd = NULL;
927 				*pf = -1;
928 				return (save(FAKE_EMPTYFILE));
929 			}
930 			return (NULL);
931 		}
932 		ch_ungetchar(c);
933 		*pfd = (void *) fd;
934 		*pf = f;
935 		return (save("-"));
936 	}
937 #endif
938 	cmd = readfd(fd);
939 	pclose(fd);
940 	if (*cmd == '\0')
941 		/*
942 		 * Pipe is empty.  This means there is no alt file.
943 		 */
944 		return (NULL);
945 	return (cmd);
946 #endif /* HAVE_POPEN */
947 }
948 
949 /*
950  * Close a replacement file.
951  */
952 	public void
953 close_altfile(altfilename, filename, pipefd)
954 	char *altfilename;
955 	char *filename;
956 	void *pipefd;
957 {
958 #if HAVE_POPEN
959 	char *lessclose;
960 	FILE *fd;
961 	char *cmd;
962 	size_t len;
963 
964 	if (secure)
965 		return;
966 	if (pipefd != NULL)
967 	{
968 #if OS2
969 		/*
970 		 * The pclose function of OS/2 emx sometimes fails.
971 		 * Send SIGINT to the piped process before closing it.
972 		 */
973 		kill(((FILE*)pipefd)->_pid, SIGINT);
974 #endif
975 		pclose((FILE*) pipefd);
976 	}
977 	if ((lessclose = lgetenv("LESSCLOSE")) == NULL)
978 	     	return;
979 	if (num_pct_s(lessclose) > 2)
980 	{
981 		error("Invalid LESSCLOSE variable");
982 		return;
983 	}
984 	len = strlen(lessclose) + strlen(filename) + strlen(altfilename) + 2;
985 	cmd = (char *) ecalloc(len, sizeof(char));
986 	SNPRINTF2(cmd, len, lessclose, filename, altfilename);
987 	fd = shellcmd(cmd);
988 	free(cmd);
989 	if (fd != NULL)
990 		pclose(fd);
991 #endif
992 }
993 
994 /*
995  * Is the specified file a directory?
996  */
997 	public int
998 is_dir(filename)
999 	char *filename;
1000 {
1001 	int isdir = 0;
1002 
1003 	filename = shell_unquote(filename);
1004 #if HAVE_STAT
1005 {
1006 	int r;
1007 	struct stat statbuf;
1008 
1009 	r = stat(filename, &statbuf);
1010 	isdir = (r >= 0 && S_ISDIR(statbuf.st_mode));
1011 }
1012 #else
1013 #ifdef _OSK
1014 {
1015 	register int f;
1016 
1017 	f = open(filename, S_IREAD | S_IFDIR);
1018 	if (f >= 0)
1019 		close(f);
1020 	isdir = (f >= 0);
1021 }
1022 #endif
1023 #endif
1024 	free(filename);
1025 	return (isdir);
1026 }
1027 
1028 /*
1029  * Returns NULL if the file can be opened and
1030  * is an ordinary file, otherwise an error message
1031  * (if it cannot be opened or is a directory, etc.)
1032  */
1033 	public char *
1034 bad_file(filename)
1035 	char *filename;
1036 {
1037 	register char *m = NULL;
1038 	size_t len;
1039 
1040 	filename = shell_unquote(filename);
1041 	if (!force_open && is_dir(filename))
1042 	{
1043 		static char is_a_dir[] = " is a directory";
1044 
1045 		len = strlen(filename) + sizeof(is_a_dir);
1046 		m = (char *) ecalloc(len, sizeof(char));
1047 		strlcpy(m, filename, len);
1048 		strlcat(m, is_a_dir, len);
1049 	} else
1050 	{
1051 #if HAVE_STAT
1052 		int r;
1053 		struct stat statbuf;
1054 
1055 		r = stat(filename, &statbuf);
1056 		if (r < 0)
1057 		{
1058 			m = errno_message(filename);
1059 		} else if (force_open)
1060 		{
1061 			m = NULL;
1062 		} else if (!S_ISREG(statbuf.st_mode))
1063 		{
1064 			static char not_reg[] = " is not a regular file (use -f to see it)";
1065 			len = strlen(filename) + sizeof(not_reg);
1066 			m = (char *) ecalloc(len, sizeof(char));
1067 			strlcpy(m, filename, len);
1068 			strlcat(m, not_reg, len);
1069 		}
1070 #endif
1071 	}
1072 	free(filename);
1073 	return (m);
1074 }
1075 
1076 /*
1077  * Return the size of a file, as cheaply as possible.
1078  * In Unix, we can stat the file.
1079  */
1080 	public POSITION
1081 filesize(f)
1082 	int f;
1083 {
1084 #if HAVE_STAT
1085 	struct stat statbuf;
1086 
1087 	if (fstat(f, &statbuf) >= 0)
1088 		return ((POSITION) statbuf.st_size);
1089 #else
1090 #ifdef _OSK
1091 	long size;
1092 
1093 	if ((size = (long) _gs_size(f)) >= 0)
1094 		return ((POSITION) size);
1095 #endif
1096 #endif
1097 	return (seek_filesize(f));
1098 }
1099 
1100 /*
1101  *
1102  */
1103 	public char *
1104 shell_coption()
1105 {
1106 	return ("-c");
1107 }
1108 
1109 /*
1110  * Return last component of a pathname.
1111  */
1112 	public char *
1113 last_component(name)
1114 	char *name;
1115 {
1116 	char *slash;
1117 
1118 	for (slash = name + strlen(name);  slash > name; )
1119 	{
1120 		--slash;
1121 		if (*slash == *PATHNAME_SEP || *slash == '/')
1122 			return (slash + 1);
1123 	}
1124 	return (name);
1125 }
1126 
1127