xref: /freebsd/contrib/less/filename.c (revision 1f4bcc459a76b7aa664f3fd557684cd0ba6da352)
1 /*
2  * Copyright (C) 1984-2015  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 = (int) 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 = (int) 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 = (int) 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 				strcpy(p, esc);
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 	int len;
231 	int f;
232 
233 	if (dirname == NULL || *dirname == '\0')
234 		return (NULL);
235 	/*
236 	 * Construct the full pathname.
237 	 */
238 	len = (int) (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 /*
261  * Return the full pathname of the given file in the "home directory".
262  */
263 	public char *
264 homefile(filename)
265 	char *filename;
266 {
267 	register char *pathname;
268 
269 	/*
270 	 * Try $HOME/filename.
271 	 */
272 	pathname = dirfile(lgetenv("HOME"), filename);
273 	if (pathname != NULL)
274 		return (pathname);
275 #if OS2
276 	/*
277 	 * Try $INIT/filename.
278 	 */
279 	pathname = dirfile(lgetenv("INIT"), filename);
280 	if (pathname != NULL)
281 		return (pathname);
282 #endif
283 #if MSDOS_COMPILER || OS2
284 	/*
285 	 * Look for the file anywhere on search path.
286 	 */
287 	pathname = (char *) calloc(_MAX_PATH, sizeof(char));
288 #if MSDOS_COMPILER==DJGPPC
289 	{
290 		char *res = searchpath(filename);
291 		if (res == 0)
292 			*pathname = '\0';
293 		else
294 			strcpy(pathname, res);
295 	}
296 #else
297 	_searchenv(filename, "PATH", pathname);
298 #endif
299 	if (*pathname != '\0')
300 		return (pathname);
301 	free(pathname);
302 #endif
303 	return (NULL);
304 }
305 
306 /*
307  * Expand a string, substituting any "%" with the current filename,
308  * and any "#" with the previous filename.
309  * But a string of N "%"s is just replaced with N-1 "%"s.
310  * Likewise for a string of N "#"s.
311  * {{ This is a lot of work just to support % and #. }}
312  */
313 	public char *
314 fexpand(s)
315 	char *s;
316 {
317 	register char *fr, *to;
318 	register int n;
319 	register char *e;
320 	IFILE ifile;
321 
322 #define	fchar_ifile(c) \
323 	((c) == '%' ? curr_ifile : \
324 	 (c) == '#' ? old_ifile : NULL_IFILE)
325 
326 	/*
327 	 * Make one pass to see how big a buffer we
328 	 * need to allocate for the expanded string.
329 	 */
330 	n = 0;
331 	for (fr = s;  *fr != '\0';  fr++)
332 	{
333 		switch (*fr)
334 		{
335 		case '%':
336 		case '#':
337 			if (fr > s && fr[-1] == *fr)
338 			{
339 				/*
340 				 * Second (or later) char in a string
341 				 * of identical chars.  Treat as normal.
342 				 */
343 				n++;
344 			} else if (fr[1] != *fr)
345 			{
346 				/*
347 				 * Single char (not repeated).  Treat specially.
348 				 */
349 				ifile = fchar_ifile(*fr);
350 				if (ifile == NULL_IFILE)
351 					n++;
352 				else
353 					n += (int) strlen(get_filename(ifile));
354 			}
355 			/*
356 			 * Else it is the first char in a string of
357 			 * identical chars.  Just discard it.
358 			 */
359 			break;
360 		default:
361 			n++;
362 			break;
363 		}
364 	}
365 
366 	e = (char *) ecalloc(n+1, sizeof(char));
367 
368 	/*
369 	 * Now copy the string, expanding any "%" or "#".
370 	 */
371 	to = e;
372 	for (fr = s;  *fr != '\0';  fr++)
373 	{
374 		switch (*fr)
375 		{
376 		case '%':
377 		case '#':
378 			if (fr > s && fr[-1] == *fr)
379 			{
380 				*to++ = *fr;
381 			} else if (fr[1] != *fr)
382 			{
383 				ifile = fchar_ifile(*fr);
384 				if (ifile == NULL_IFILE)
385 					*to++ = *fr;
386 				else
387 				{
388 					strcpy(to, get_filename(ifile));
389 					to += strlen(to);
390 				}
391 			}
392 			break;
393 		default:
394 			*to++ = *fr;
395 			break;
396 		}
397 	}
398 	*to = '\0';
399 	return (e);
400 }
401 
402 
403 #if TAB_COMPLETE_FILENAME
404 
405 /*
406  * Return a blank-separated list of filenames which "complete"
407  * the given string.
408  */
409 	public char *
410 fcomplete(s)
411 	char *s;
412 {
413 	char *fpat;
414 	char *qs;
415 
416 	if (secure)
417 		return (NULL);
418 	/*
419 	 * Complete the filename "s" by globbing "s*".
420 	 */
421 #if MSDOS_COMPILER && (MSDOS_COMPILER == MSOFTC || MSDOS_COMPILER == BORLANDC)
422 	/*
423 	 * But in DOS, we have to glob "s*.*".
424 	 * But if the final component of the filename already has
425 	 * a dot in it, just do "s*".
426 	 * (Thus, "FILE" is globbed as "FILE*.*",
427 	 *  but "FILE.A" is globbed as "FILE.A*").
428 	 */
429 	{
430 		char *slash;
431 		int len;
432 		for (slash = s+strlen(s)-1;  slash > s;  slash--)
433 			if (*slash == *PATHNAME_SEP || *slash == '/')
434 				break;
435 		len = (int) strlen(s) + 4;
436 		fpat = (char *) ecalloc(len, sizeof(char));
437 		if (strchr(slash, '.') == NULL)
438 			SNPRINTF1(fpat, len, "%s*.*", s);
439 		else
440 			SNPRINTF1(fpat, len, "%s*", s);
441 	}
442 #else
443 	{
444 	int len = (int) strlen(s) + 2;
445 	fpat = (char *) ecalloc(len, sizeof(char));
446 	SNPRINTF1(fpat, len, "%s*", s);
447 	}
448 #endif
449 	qs = lglob(fpat);
450 	s = shell_unquote(qs);
451 	if (strcmp(s,fpat) == 0)
452 	{
453 		/*
454 		 * The filename didn't expand.
455 		 */
456 		free(qs);
457 		qs = NULL;
458 	}
459 	free(s);
460 	free(fpat);
461 	return (qs);
462 }
463 #endif
464 
465 /*
466  * Try to determine if a file is "binary".
467  * This is just a guess, and we need not try too hard to make it accurate.
468  */
469 	public int
470 bin_file(f)
471 	int f;
472 {
473 	int n;
474 	int bin_count = 0;
475 	char data[256];
476 	char* p;
477 	char* pend;
478 
479 	if (!seekable(f))
480 		return (0);
481 	if (lseek(f, (off_t)0, SEEK_SET) == BAD_LSEEK)
482 		return (0);
483 	n = read(f, data, sizeof(data));
484 	if (n <= 0)
485 		return (0);
486 	if (utf_mode)
487 	{
488 		bin_count = utf_bin_count(data, n);
489 	} else
490 	{
491 		pend = &data[n];
492 		for (p = data;  p < pend;  )
493 		{
494 			LWCHAR c = step_char(&p, +1, pend);
495 			if (ctldisp == OPT_ONPLUS && IS_CSI_START(c))
496 			{
497 				do {
498 					c = step_char(&p, +1, pend);
499 				} while (p < pend && is_ansi_middle(c));
500 			} else if (binary_char(c))
501 				bin_count++;
502 		}
503 	}
504 	/*
505 	 * Call it a binary file if there are more than 5 binary characters
506 	 * in the first 256 bytes of the file.
507 	 */
508 	return (bin_count > 5);
509 }
510 
511 /*
512  * Try to determine the size of a file by seeking to the end.
513  */
514 	static POSITION
515 seek_filesize(f)
516 	int f;
517 {
518 	off_t spos;
519 
520 	spos = lseek(f, (off_t)0, SEEK_END);
521 	if (spos == BAD_LSEEK)
522 		return (NULL_POSITION);
523 	return ((POSITION) spos);
524 }
525 
526 /*
527  * Read a string from a file.
528  * Return a pointer to the string in memory.
529  */
530 	static char *
531 readfd(fd)
532 	FILE *fd;
533 {
534 	int len;
535 	int ch;
536 	char *buf;
537 	char *p;
538 
539 	/*
540 	 * Make a guess about how many chars in the string
541 	 * and allocate a buffer to hold it.
542 	 */
543 	len = 100;
544 	buf = (char *) ecalloc(len, sizeof(char));
545 	for (p = buf;  ;  p++)
546 	{
547 		if ((ch = getc(fd)) == '\n' || ch == EOF)
548 			break;
549 		if (p - buf >= len-1)
550 		{
551 			/*
552 			 * The string is too big to fit in the buffer we have.
553 			 * Allocate a new buffer, twice as big.
554 			 */
555 			len *= 2;
556 			*p = '\0';
557 			p = (char *) ecalloc(len, sizeof(char));
558 			strcpy(p, buf);
559 			free(buf);
560 			buf = p;
561 			p = buf + strlen(buf);
562 		}
563 		*p = ch;
564 	}
565 	*p = '\0';
566 	return (buf);
567 }
568 
569 
570 
571 #if HAVE_POPEN
572 
573 FILE *popen();
574 
575 /*
576  * Execute a shell command.
577  * Return a pointer to a pipe connected to the shell command's standard output.
578  */
579 	static FILE *
580 shellcmd(cmd)
581 	char *cmd;
582 {
583 	FILE *fd;
584 
585 #if HAVE_SHELL
586 	char *shell;
587 
588 	shell = lgetenv("SHELL");
589 	if (shell != NULL && *shell != '\0')
590 	{
591 		char *scmd;
592 		char *esccmd;
593 
594 		/*
595 		 * Read the output of <$SHELL -c cmd>.
596 		 * Escape any metacharacters in the command.
597 		 */
598 		esccmd = shell_quote(cmd);
599 		if (esccmd == NULL)
600 		{
601 			fd = popen(cmd, "r");
602 		} else
603 		{
604 			int len = (int) (strlen(shell) + strlen(esccmd) + 5);
605 			scmd = (char *) ecalloc(len, sizeof(char));
606 			SNPRINTF3(scmd, len, "%s %s %s", shell, shell_coption(), esccmd);
607 			free(esccmd);
608 			fd = popen(scmd, "r");
609 			free(scmd);
610 		}
611 	} else
612 #endif
613 	{
614 		fd = popen(cmd, "r");
615 	}
616 	/*
617 	 * Redirection in `popen' might have messed with the
618 	 * standard devices.  Restore binary input mode.
619 	 */
620 	SET_BINARY(0);
621 	return (fd);
622 }
623 
624 #endif /* HAVE_POPEN */
625 
626 
627 /*
628  * Expand a filename, doing any system-specific metacharacter substitutions.
629  */
630 	public char *
631 lglob(filename)
632 	char *filename;
633 {
634 	char *gfilename;
635 	char *ofilename;
636 
637 	ofilename = fexpand(filename);
638 	if (secure)
639 		return (ofilename);
640 	filename = shell_unquote(ofilename);
641 
642 #ifdef DECL_GLOB_LIST
643 {
644 	/*
645 	 * The globbing function returns a list of names.
646 	 */
647 	int length;
648 	char *p;
649 	char *qfilename;
650 	DECL_GLOB_LIST(list)
651 
652 	GLOB_LIST(filename, list);
653 	if (GLOB_LIST_FAILED(list))
654 	{
655 		free(filename);
656 		return (ofilename);
657 	}
658 	length = 1; /* Room for trailing null byte */
659 	for (SCAN_GLOB_LIST(list, p))
660 	{
661 		INIT_GLOB_LIST(list, p);
662 		qfilename = shell_quote(p);
663 		if (qfilename != NULL)
664 		{
665 	  		length += strlen(qfilename) + 1;
666 			free(qfilename);
667 		}
668 	}
669 	gfilename = (char *) ecalloc(length, sizeof(char));
670 	for (SCAN_GLOB_LIST(list, p))
671 	{
672 		INIT_GLOB_LIST(list, p);
673 		qfilename = shell_quote(p);
674 		if (qfilename != NULL)
675 		{
676 			sprintf(gfilename + strlen(gfilename), "%s ", qfilename);
677 			free(qfilename);
678 		}
679 	}
680 	/*
681 	 * Overwrite the final trailing space with a null terminator.
682 	 */
683 	*--p = '\0';
684 	GLOB_LIST_DONE(list);
685 }
686 #else
687 #ifdef DECL_GLOB_NAME
688 {
689 	/*
690 	 * The globbing function returns a single name, and
691 	 * is called multiple times to walk thru all names.
692 	 */
693 	register char *p;
694 	register int len;
695 	register int n;
696 	char *pathname;
697 	char *qpathname;
698 	DECL_GLOB_NAME(fnd,drive,dir,fname,ext,handle)
699 
700 	GLOB_FIRST_NAME(filename, &fnd, handle);
701 	if (GLOB_FIRST_FAILED(handle))
702 	{
703 		free(filename);
704 		return (ofilename);
705 	}
706 
707 	_splitpath(filename, drive, dir, fname, ext);
708 	len = 100;
709 	gfilename = (char *) ecalloc(len, sizeof(char));
710 	p = gfilename;
711 	do {
712 		n = (int) (strlen(drive) + strlen(dir) + strlen(fnd.GLOB_NAME) + 1);
713 		pathname = (char *) ecalloc(n, sizeof(char));
714 		SNPRINTF3(pathname, n, "%s%s%s", drive, dir, fnd.GLOB_NAME);
715 		qpathname = shell_quote(pathname);
716 		free(pathname);
717 		if (qpathname != NULL)
718 		{
719 			n = (int) strlen(qpathname);
720 			while (p - gfilename + n + 2 >= len)
721 			{
722 				/*
723 				 * No room in current buffer.
724 				 * Allocate a bigger one.
725 				 */
726 				len *= 2;
727 				*p = '\0';
728 				p = (char *) ecalloc(len, sizeof(char));
729 				strcpy(p, gfilename);
730 				free(gfilename);
731 				gfilename = p;
732 				p = gfilename + strlen(gfilename);
733 			}
734 			strcpy(p, qpathname);
735 			free(qpathname);
736 			p += n;
737 			*p++ = ' ';
738 		}
739 	} while (GLOB_NEXT_NAME(handle, &fnd) == 0);
740 
741 	/*
742 	 * Overwrite the final trailing space with a null terminator.
743 	 */
744 	*--p = '\0';
745 	GLOB_NAME_DONE(handle);
746 }
747 #else
748 #if HAVE_POPEN
749 {
750 	/*
751 	 * We get the shell to glob the filename for us by passing
752 	 * an "echo" command to the shell and reading its output.
753 	 */
754 	FILE *fd;
755 	char *s;
756 	char *lessecho;
757 	char *cmd;
758 	char *esc;
759 	int len;
760 
761 	esc = get_meta_escape();
762 	if (strlen(esc) == 0)
763 		esc = "-";
764 	esc = shell_quote(esc);
765 	if (esc == NULL)
766 	{
767 		free(filename);
768 		return (ofilename);
769 	}
770 	lessecho = lgetenv("LESSECHO");
771 	if (lessecho == NULL || *lessecho == '\0')
772 		lessecho = "lessecho";
773 	/*
774 	 * Invoke lessecho, and read its output (a globbed list of filenames).
775 	 */
776 	len = (int) (strlen(lessecho) + strlen(ofilename) + (7*strlen(metachars())) + 24);
777 	cmd = (char *) ecalloc(len, sizeof(char));
778 	SNPRINTF4(cmd, len, "%s -p0x%x -d0x%x -e%s ", lessecho, openquote, closequote, esc);
779 	free(esc);
780 	for (s = metachars();  *s != '\0';  s++)
781 		sprintf(cmd + strlen(cmd), "-n0x%x ", *s);
782 	sprintf(cmd + strlen(cmd), "-- %s", ofilename);
783 	fd = shellcmd(cmd);
784 	free(cmd);
785 	if (fd == NULL)
786 	{
787 		/*
788 		 * Cannot create the pipe.
789 		 * Just return the original (fexpanded) filename.
790 		 */
791 		free(filename);
792 		return (ofilename);
793 	}
794 	gfilename = readfd(fd);
795 	pclose(fd);
796 	if (*gfilename == '\0')
797 	{
798 		free(gfilename);
799 		free(filename);
800 		return (ofilename);
801 	}
802 }
803 #else
804 	/*
805 	 * No globbing functions at all.  Just use the fexpanded filename.
806 	 */
807 	gfilename = save(filename);
808 #endif
809 #endif
810 #endif
811 	free(filename);
812 	free(ofilename);
813 	return (gfilename);
814 }
815 
816 /*
817  * Return number of %s escapes in a string.
818  * Return a large number if there are any other % escapes besides %s.
819  */
820 	static int
821 num_pct_s(lessopen)
822 	char *lessopen;
823 {
824 	int num = 0;
825 
826 	while (*lessopen != '\0')
827 	{
828 		if (*lessopen == '%')
829 		{
830 			if (lessopen[1] == '%')
831 				++lessopen;
832 			else if (lessopen[1] == 's')
833 				++num;
834 			else
835 				return (999);
836 		}
837 		++lessopen;
838 	}
839 	return (num);
840 }
841 
842 /*
843  * See if we should open a "replacement file"
844  * instead of the file we're about to open.
845  */
846 	public char *
847 open_altfile(filename, pf, pfd)
848 	char *filename;
849 	int *pf;
850 	void **pfd;
851 {
852 #if !HAVE_POPEN
853 	return (NULL);
854 #else
855 	char *lessopen;
856 	char *cmd;
857 	int len;
858 	FILE *fd;
859 #if HAVE_FILENO
860 	int returnfd = 0;
861 #endif
862 
863 	if (!use_lessopen || secure)
864 		return (NULL);
865 	ch_ungetchar(-1);
866 	if ((lessopen = lgetenv("LESSOPEN")) == NULL)
867 		return (NULL);
868 	while (*lessopen == '|')
869 	{
870 		/*
871 		 * If LESSOPEN starts with a |, it indicates
872 		 * a "pipe preprocessor".
873 		 */
874 #if !HAVE_FILENO
875 		error("LESSOPEN pipe is not supported", NULL_PARG);
876 		return (NULL);
877 #else
878 		lessopen++;
879 		returnfd++;
880 #endif
881 	}
882 	if (*lessopen == '-') {
883 		/*
884 		 * Lessopen preprocessor will accept "-" as a filename.
885 		 */
886 		lessopen++;
887 	} else {
888 		if (strcmp(filename, "-") == 0)
889 			return (NULL);
890 	}
891 	if (num_pct_s(lessopen) > 1)
892 	{
893 		error("Invalid LESSOPEN variable", NULL_PARG);
894 		return (NULL);
895 	}
896 
897 	len = (int) (strlen(lessopen) + strlen(filename) + 2);
898 	cmd = (char *) ecalloc(len, sizeof(char));
899 	SNPRINTF1(cmd, len, lessopen, filename);
900 	fd = shellcmd(cmd);
901 	free(cmd);
902 	if (fd == NULL)
903 	{
904 		/*
905 		 * Cannot create the pipe.
906 		 */
907 		return (NULL);
908 	}
909 #if HAVE_FILENO
910 	if (returnfd)
911 	{
912 		int f;
913 		char c;
914 
915 		/*
916 		 * Read one char to see if the pipe will produce any data.
917 		 * If it does, push the char back on the pipe.
918 		 */
919 		f = fileno(fd);
920 		SET_BINARY(f);
921 		if (read(f, &c, 1) != 1)
922 		{
923 			/*
924 			 * Pipe is empty.
925 			 * If more than 1 pipe char was specified,
926 			 * the exit status tells whether the file itself
927 			 * is empty, or if there is no alt file.
928 			 * If only one pipe char, just assume no alt file.
929 			 */
930 			int status = pclose(fd);
931 			if (returnfd > 1 && status == 0) {
932 				*pfd = NULL;
933 				*pf = -1;
934 				return (save(FAKE_EMPTYFILE));
935 			}
936 			return (NULL);
937 		}
938 		ch_ungetchar(c);
939 		*pfd = (void *) fd;
940 		*pf = f;
941 		return (save("-"));
942 	}
943 #endif
944 	cmd = readfd(fd);
945 	pclose(fd);
946 	if (*cmd == '\0')
947 		/*
948 		 * Pipe is empty.  This means there is no alt file.
949 		 */
950 		return (NULL);
951 	return (cmd);
952 #endif /* HAVE_POPEN */
953 }
954 
955 /*
956  * Close a replacement file.
957  */
958 	public void
959 close_altfile(altfilename, filename, pipefd)
960 	char *altfilename;
961 	char *filename;
962 	void *pipefd;
963 {
964 #if HAVE_POPEN
965 	char *lessclose;
966 	FILE *fd;
967 	char *cmd;
968 	int len;
969 
970 	if (secure)
971 		return;
972 	if (pipefd != NULL)
973 	{
974 #if OS2
975 		/*
976 		 * The pclose function of OS/2 emx sometimes fails.
977 		 * Send SIGINT to the piped process before closing it.
978 		 */
979 		kill(((FILE*)pipefd)->_pid, SIGINT);
980 #endif
981 		pclose((FILE*) pipefd);
982 	}
983 	if ((lessclose = lgetenv("LESSCLOSE")) == NULL)
984 	     	return;
985 	if (num_pct_s(lessclose) > 2)
986 	{
987 		error("Invalid LESSCLOSE variable", NULL_PARG);
988 		return;
989 	}
990 	len = (int) (strlen(lessclose) + strlen(filename) + strlen(altfilename) + 2);
991 	cmd = (char *) ecalloc(len, sizeof(char));
992 	SNPRINTF2(cmd, len, lessclose, filename, altfilename);
993 	fd = shellcmd(cmd);
994 	free(cmd);
995 	if (fd != NULL)
996 		pclose(fd);
997 #endif
998 }
999 
1000 /*
1001  * Is the specified file a directory?
1002  */
1003 	public int
1004 is_dir(filename)
1005 	char *filename;
1006 {
1007 	int isdir = 0;
1008 
1009 	filename = shell_unquote(filename);
1010 #if HAVE_STAT
1011 {
1012 	int r;
1013 	struct stat statbuf;
1014 
1015 	r = stat(filename, &statbuf);
1016 	isdir = (r >= 0 && S_ISDIR(statbuf.st_mode));
1017 }
1018 #else
1019 #ifdef _OSK
1020 {
1021 	register int f;
1022 
1023 	f = open(filename, S_IREAD | S_IFDIR);
1024 	if (f >= 0)
1025 		close(f);
1026 	isdir = (f >= 0);
1027 }
1028 #endif
1029 #endif
1030 	free(filename);
1031 	return (isdir);
1032 }
1033 
1034 /*
1035  * Returns NULL if the file can be opened and
1036  * is an ordinary file, otherwise an error message
1037  * (if it cannot be opened or is a directory, etc.)
1038  */
1039 	public char *
1040 bad_file(filename)
1041 	char *filename;
1042 {
1043 	register char *m = NULL;
1044 
1045 	filename = shell_unquote(filename);
1046 	if (!force_open && is_dir(filename))
1047 	{
1048 		static char is_a_dir[] = " is a directory";
1049 
1050 		m = (char *) ecalloc(strlen(filename) + sizeof(is_a_dir),
1051 			sizeof(char));
1052 		strcpy(m, filename);
1053 		strcat(m, is_a_dir);
1054 	} else
1055 	{
1056 #if HAVE_STAT
1057 		int r;
1058 		struct stat statbuf;
1059 
1060 		r = stat(filename, &statbuf);
1061 		if (r < 0)
1062 		{
1063 			m = errno_message(filename);
1064 		} else if (force_open)
1065 		{
1066 			m = NULL;
1067 		} else if (!S_ISREG(statbuf.st_mode))
1068 		{
1069 			static char not_reg[] = " is not a regular file (use -f to see it)";
1070 			m = (char *) ecalloc(strlen(filename) + sizeof(not_reg),
1071 				sizeof(char));
1072 			strcpy(m, filename);
1073 			strcat(m, not_reg);
1074 		}
1075 #endif
1076 	}
1077 	free(filename);
1078 	return (m);
1079 }
1080 
1081 /*
1082  * Return the size of a file, as cheaply as possible.
1083  * In Unix, we can stat the file.
1084  */
1085 	public POSITION
1086 filesize(f)
1087 	int f;
1088 {
1089 #if HAVE_STAT
1090 	struct stat statbuf;
1091 
1092 	if (fstat(f, &statbuf) >= 0)
1093 		return ((POSITION) statbuf.st_size);
1094 #else
1095 #ifdef _OSK
1096 	long size;
1097 
1098 	if ((size = (long) _gs_size(f)) >= 0)
1099 		return ((POSITION) size);
1100 #endif
1101 #endif
1102 	return (seek_filesize(f));
1103 }
1104 
1105 /*
1106  *
1107  */
1108 	public char *
1109 shell_coption()
1110 {
1111 	return ("-c");
1112 }
1113 
1114 /*
1115  * Return last component of a pathname.
1116  */
1117 	public char *
1118 last_component(name)
1119 	char *name;
1120 {
1121 	char *slash;
1122 
1123 	for (slash = name + strlen(name);  slash > name; )
1124 	{
1125 		--slash;
1126 		if (*slash == *PATHNAME_SEP || *slash == '/')
1127 			return (slash + 1);
1128 	}
1129 	return (name);
1130 }
1131 
1132