xref: /freebsd/contrib/less/filename.c (revision 38f0b757fd84d17d0fc24739a7cda160c4516d81)
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 				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= 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 += 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 = 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 = 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 	pend = &data[n];
485 	for (p = data;  p < pend;  )
486 	{
487 		LWCHAR c = step_char(&p, +1, pend);
488 		if (ctldisp == OPT_ONPLUS && IS_CSI_START(c))
489 		{
490 			do {
491 				c = step_char(&p, +1, pend);
492 			} while (p < pend && is_ansi_middle(c));
493 		} else if (binary_char(c))
494 			bin_count++;
495 	}
496 	/*
497 	 * Call it a binary file if there are more than 5 binary characters
498 	 * in the first 256 bytes of the file.
499 	 */
500 	return (bin_count > 5);
501 }
502 
503 /*
504  * Try to determine the size of a file by seeking to the end.
505  */
506 	static POSITION
507 seek_filesize(f)
508 	int f;
509 {
510 	off_t spos;
511 
512 	spos = lseek(f, (off_t)0, SEEK_END);
513 	if (spos == BAD_LSEEK)
514 		return (NULL_POSITION);
515 	return ((POSITION) spos);
516 }
517 
518 /*
519  * Read a string from a file.
520  * Return a pointer to the string in memory.
521  */
522 	static char *
523 readfd(fd)
524 	FILE *fd;
525 {
526 	int len;
527 	int ch;
528 	char *buf;
529 	char *p;
530 
531 	/*
532 	 * Make a guess about how many chars in the string
533 	 * and allocate a buffer to hold it.
534 	 */
535 	len = 100;
536 	buf = (char *) ecalloc(len, sizeof(char));
537 	for (p = buf;  ;  p++)
538 	{
539 		if ((ch = getc(fd)) == '\n' || ch == EOF)
540 			break;
541 		if (p - buf >= len-1)
542 		{
543 			/*
544 			 * The string is too big to fit in the buffer we have.
545 			 * Allocate a new buffer, twice as big.
546 			 */
547 			len *= 2;
548 			*p = '\0';
549 			p = (char *) ecalloc(len, sizeof(char));
550 			strcpy(p, buf);
551 			free(buf);
552 			buf = p;
553 			p = buf + strlen(buf);
554 		}
555 		*p = ch;
556 	}
557 	*p = '\0';
558 	return (buf);
559 }
560 
561 
562 
563 #if HAVE_POPEN
564 
565 FILE *popen();
566 
567 /*
568  * Execute a shell command.
569  * Return a pointer to a pipe connected to the shell command's standard output.
570  */
571 	static FILE *
572 shellcmd(cmd)
573 	char *cmd;
574 {
575 	FILE *fd;
576 
577 #if HAVE_SHELL
578 	char *shell;
579 
580 	shell = lgetenv("SHELL");
581 	if (shell != NULL && *shell != '\0')
582 	{
583 		char *scmd;
584 		char *esccmd;
585 
586 		/*
587 		 * Read the output of <$SHELL -c cmd>.
588 		 * Escape any metacharacters in the command.
589 		 */
590 		esccmd = shell_quote(cmd);
591 		if (esccmd == NULL)
592 		{
593 			fd = popen(cmd, "r");
594 		} else
595 		{
596 			int len = strlen(shell) + strlen(esccmd) + 5;
597 			scmd = (char *) ecalloc(len, sizeof(char));
598 			SNPRINTF3(scmd, len, "%s %s %s", shell, shell_coption(), esccmd);
599 			free(esccmd);
600 			fd = popen(scmd, "r");
601 			free(scmd);
602 		}
603 	} else
604 #endif
605 	{
606 		fd = popen(cmd, "r");
607 	}
608 	/*
609 	 * Redirection in `popen' might have messed with the
610 	 * standard devices.  Restore binary input mode.
611 	 */
612 	SET_BINARY(0);
613 	return (fd);
614 }
615 
616 #endif /* HAVE_POPEN */
617 
618 
619 /*
620  * Expand a filename, doing any system-specific metacharacter substitutions.
621  */
622 	public char *
623 lglob(filename)
624 	char *filename;
625 {
626 	char *gfilename;
627 	char *ofilename;
628 
629 	ofilename = fexpand(filename);
630 	if (secure)
631 		return (ofilename);
632 	filename = shell_unquote(ofilename);
633 
634 #ifdef DECL_GLOB_LIST
635 {
636 	/*
637 	 * The globbing function returns a list of names.
638 	 */
639 	int length;
640 	char *p;
641 	char *qfilename;
642 	DECL_GLOB_LIST(list)
643 
644 	GLOB_LIST(filename, list);
645 	if (GLOB_LIST_FAILED(list))
646 	{
647 		free(filename);
648 		return (ofilename);
649 	}
650 	length = 1; /* Room for trailing null byte */
651 	for (SCAN_GLOB_LIST(list, p))
652 	{
653 		INIT_GLOB_LIST(list, p);
654 		qfilename = shell_quote(p);
655 		if (qfilename != NULL)
656 		{
657 	  		length += strlen(qfilename) + 1;
658 			free(qfilename);
659 		}
660 	}
661 	gfilename = (char *) ecalloc(length, sizeof(char));
662 	for (SCAN_GLOB_LIST(list, p))
663 	{
664 		INIT_GLOB_LIST(list, p);
665 		qfilename = shell_quote(p);
666 		if (qfilename != NULL)
667 		{
668 			sprintf(gfilename + strlen(gfilename), "%s ", qfilename);
669 			free(qfilename);
670 		}
671 	}
672 	/*
673 	 * Overwrite the final trailing space with a null terminator.
674 	 */
675 	*--p = '\0';
676 	GLOB_LIST_DONE(list);
677 }
678 #else
679 #ifdef DECL_GLOB_NAME
680 {
681 	/*
682 	 * The globbing function returns a single name, and
683 	 * is called multiple times to walk thru all names.
684 	 */
685 	register char *p;
686 	register int len;
687 	register int n;
688 	char *pathname;
689 	char *qpathname;
690 	DECL_GLOB_NAME(fnd,drive,dir,fname,ext,handle)
691 
692 	GLOB_FIRST_NAME(filename, &fnd, handle);
693 	if (GLOB_FIRST_FAILED(handle))
694 	{
695 		free(filename);
696 		return (ofilename);
697 	}
698 
699 	_splitpath(filename, drive, dir, fname, ext);
700 	len = 100;
701 	gfilename = (char *) ecalloc(len, sizeof(char));
702 	p = gfilename;
703 	do {
704 		n = strlen(drive) + strlen(dir) + strlen(fnd.GLOB_NAME) + 1;
705 		pathname = (char *) ecalloc(n, sizeof(char));
706 		SNPRINTF3(pathname, n, "%s%s%s", drive, dir, fnd.GLOB_NAME);
707 		qpathname = shell_quote(pathname);
708 		free(pathname);
709 		if (qpathname != NULL)
710 		{
711 			n = strlen(qpathname);
712 			while (p - gfilename + n + 2 >= len)
713 			{
714 				/*
715 				 * No room in current buffer.
716 				 * Allocate a bigger one.
717 				 */
718 				len *= 2;
719 				*p = '\0';
720 				p = (char *) ecalloc(len, sizeof(char));
721 				strcpy(p, gfilename);
722 				free(gfilename);
723 				gfilename = p;
724 				p = gfilename + strlen(gfilename);
725 			}
726 			strcpy(p, qpathname);
727 			free(qpathname);
728 			p += n;
729 			*p++ = ' ';
730 		}
731 	} while (GLOB_NEXT_NAME(handle, &fnd) == 0);
732 
733 	/*
734 	 * Overwrite the final trailing space with a null terminator.
735 	 */
736 	*--p = '\0';
737 	GLOB_NAME_DONE(handle);
738 }
739 #else
740 #if HAVE_POPEN
741 {
742 	/*
743 	 * We get the shell to glob the filename for us by passing
744 	 * an "echo" command to the shell and reading its output.
745 	 */
746 	FILE *fd;
747 	char *s;
748 	char *lessecho;
749 	char *cmd;
750 	char *esc;
751 	int len;
752 
753 	esc = get_meta_escape();
754 	if (strlen(esc) == 0)
755 		esc = "-";
756 	esc = shell_quote(esc);
757 	if (esc == NULL)
758 	{
759 		free(filename);
760 		return (ofilename);
761 	}
762 	lessecho = lgetenv("LESSECHO");
763 	if (lessecho == NULL || *lessecho == '\0')
764 		lessecho = "lessecho";
765 	/*
766 	 * Invoke lessecho, and read its output (a globbed list of filenames).
767 	 */
768 	len = strlen(lessecho) + strlen(ofilename) + (7*strlen(metachars())) + 24;
769 	cmd = (char *) ecalloc(len, sizeof(char));
770 	SNPRINTF4(cmd, len, "%s -p0x%x -d0x%x -e%s ", lessecho, openquote, closequote, esc);
771 	free(esc);
772 	for (s = metachars();  *s != '\0';  s++)
773 		sprintf(cmd + strlen(cmd), "-n0x%x ", *s);
774 	sprintf(cmd + strlen(cmd), "-- %s", ofilename);
775 	fd = shellcmd(cmd);
776 	free(cmd);
777 	if (fd == NULL)
778 	{
779 		/*
780 		 * Cannot create the pipe.
781 		 * Just return the original (fexpanded) filename.
782 		 */
783 		free(filename);
784 		return (ofilename);
785 	}
786 	gfilename = readfd(fd);
787 	pclose(fd);
788 	if (*gfilename == '\0')
789 	{
790 		free(gfilename);
791 		free(filename);
792 		return (ofilename);
793 	}
794 }
795 #else
796 	/*
797 	 * No globbing functions at all.  Just use the fexpanded filename.
798 	 */
799 	gfilename = save(filename);
800 #endif
801 #endif
802 #endif
803 	free(filename);
804 	free(ofilename);
805 	return (gfilename);
806 }
807 
808 /*
809  * Return number of %s escapes in a string.
810  * Return a large number if there are any other % escapes besides %s.
811  */
812 	static int
813 num_pct_s(lessopen)
814 	char *lessopen;
815 {
816 	int num;
817 
818 	for (num = 0;; num++)
819 	{
820 		lessopen = strchr(lessopen, '%');
821 		if (lessopen == NULL)
822 			break;
823 		if (*++lessopen != 's')
824 			return (999);
825 	}
826 	return (num);
827 }
828 
829 /*
830  * See if we should open a "replacement file"
831  * instead of the file we're about to open.
832  */
833 	public char *
834 open_altfile(filename, pf, pfd)
835 	char *filename;
836 	int *pf;
837 	void **pfd;
838 {
839 #if !HAVE_POPEN
840 	return (NULL);
841 #else
842 	char *lessopen;
843 	char *cmd;
844 	int len;
845 	FILE *fd;
846 #if HAVE_FILENO
847 	int returnfd = 0;
848 #endif
849 
850 	if (!use_lessopen || secure)
851 		return (NULL);
852 	ch_ungetchar(-1);
853 	if ((lessopen = lgetenv("LESSOPEN")) == NULL)
854 		return (NULL);
855 	while (*lessopen == '|')
856 	{
857 		/*
858 		 * If LESSOPEN starts with a |, it indicates
859 		 * a "pipe preprocessor".
860 		 */
861 #if !HAVE_FILENO
862 		error("LESSOPEN pipe is not supported", NULL_PARG);
863 		return (NULL);
864 #else
865 		lessopen++;
866 		returnfd++;
867 #endif
868 	}
869 	if (*lessopen == '-') {
870 		/*
871 		 * Lessopen preprocessor will accept "-" as a filename.
872 		 */
873 		lessopen++;
874 	} else {
875 		if (strcmp(filename, "-") == 0)
876 			return (NULL);
877 	}
878 	if (num_pct_s(lessopen) > 1)
879 	{
880 		error("Invalid LESSOPEN variable", NULL_PARG);
881 		return (NULL);
882 	}
883 
884 	len = strlen(lessopen) + strlen(filename) + 2;
885 	cmd = (char *) ecalloc(len, sizeof(char));
886 	SNPRINTF1(cmd, len, lessopen, filename);
887 	fd = shellcmd(cmd);
888 	free(cmd);
889 	if (fd == NULL)
890 	{
891 		/*
892 		 * Cannot create the pipe.
893 		 */
894 		return (NULL);
895 	}
896 #if HAVE_FILENO
897 	if (returnfd)
898 	{
899 		int f;
900 		char c;
901 
902 		/*
903 		 * Read one char to see if the pipe will produce any data.
904 		 * If it does, push the char back on the pipe.
905 		 */
906 		f = fileno(fd);
907 		SET_BINARY(f);
908 		if (read(f, &c, 1) != 1)
909 		{
910 			/*
911 			 * Pipe is empty.
912 			 * If more than 1 pipe char was specified,
913 			 * the exit status tells whether the file itself
914 			 * is empty, or if there is no alt file.
915 			 * If only one pipe char, just assume no alt file.
916 			 */
917 			int status = pclose(fd);
918 			if (returnfd > 1 && status == 0) {
919 				*pfd = NULL;
920 				*pf = -1;
921 				return (save(FAKE_EMPTYFILE));
922 			}
923 			return (NULL);
924 		}
925 		ch_ungetchar(c);
926 		*pfd = (void *) fd;
927 		*pf = f;
928 		return (save("-"));
929 	}
930 #endif
931 	cmd = readfd(fd);
932 	pclose(fd);
933 	if (*cmd == '\0')
934 		/*
935 		 * Pipe is empty.  This means there is no alt file.
936 		 */
937 		return (NULL);
938 	return (cmd);
939 #endif /* HAVE_POPEN */
940 }
941 
942 /*
943  * Close a replacement file.
944  */
945 	public void
946 close_altfile(altfilename, filename, pipefd)
947 	char *altfilename;
948 	char *filename;
949 	void *pipefd;
950 {
951 #if HAVE_POPEN
952 	char *lessclose;
953 	FILE *fd;
954 	char *cmd;
955 	int len;
956 
957 	if (secure)
958 		return;
959 	if (pipefd != NULL)
960 	{
961 #if OS2
962 		/*
963 		 * The pclose function of OS/2 emx sometimes fails.
964 		 * Send SIGINT to the piped process before closing it.
965 		 */
966 		kill(((FILE*)pipefd)->_pid, SIGINT);
967 #endif
968 		pclose((FILE*) pipefd);
969 	}
970 	if ((lessclose = lgetenv("LESSCLOSE")) == NULL)
971 	     	return;
972 	if (num_pct_s(lessclose) > 2)
973 	{
974 		error("Invalid LESSCLOSE variable");
975 		return;
976 	}
977 	len = strlen(lessclose) + strlen(filename) + strlen(altfilename) + 2;
978 	cmd = (char *) ecalloc(len, sizeof(char));
979 	SNPRINTF2(cmd, len, lessclose, filename, altfilename);
980 	fd = shellcmd(cmd);
981 	free(cmd);
982 	if (fd != NULL)
983 		pclose(fd);
984 #endif
985 }
986 
987 /*
988  * Is the specified file a directory?
989  */
990 	public int
991 is_dir(filename)
992 	char *filename;
993 {
994 	int isdir = 0;
995 
996 	filename = shell_unquote(filename);
997 #if HAVE_STAT
998 {
999 	int r;
1000 	struct stat statbuf;
1001 
1002 	r = stat(filename, &statbuf);
1003 	isdir = (r >= 0 && S_ISDIR(statbuf.st_mode));
1004 }
1005 #else
1006 #ifdef _OSK
1007 {
1008 	register int f;
1009 
1010 	f = open(filename, S_IREAD | S_IFDIR);
1011 	if (f >= 0)
1012 		close(f);
1013 	isdir = (f >= 0);
1014 }
1015 #endif
1016 #endif
1017 	free(filename);
1018 	return (isdir);
1019 }
1020 
1021 /*
1022  * Returns NULL if the file can be opened and
1023  * is an ordinary file, otherwise an error message
1024  * (if it cannot be opened or is a directory, etc.)
1025  */
1026 	public char *
1027 bad_file(filename)
1028 	char *filename;
1029 {
1030 	register char *m = NULL;
1031 
1032 	filename = shell_unquote(filename);
1033 	if (!force_open && is_dir(filename))
1034 	{
1035 		static char is_a_dir[] = " is a directory";
1036 
1037 		m = (char *) ecalloc(strlen(filename) + sizeof(is_a_dir),
1038 			sizeof(char));
1039 		strcpy(m, filename);
1040 		strcat(m, is_a_dir);
1041 	} else
1042 	{
1043 #if HAVE_STAT
1044 		int r;
1045 		struct stat statbuf;
1046 
1047 		r = stat(filename, &statbuf);
1048 		if (r < 0)
1049 		{
1050 			m = errno_message(filename);
1051 		} else if (force_open)
1052 		{
1053 			m = NULL;
1054 		} else if (!S_ISREG(statbuf.st_mode))
1055 		{
1056 			static char not_reg[] = " is not a regular file (use -f to see it)";
1057 			m = (char *) ecalloc(strlen(filename) + sizeof(not_reg),
1058 				sizeof(char));
1059 			strcpy(m, filename);
1060 			strcat(m, not_reg);
1061 		}
1062 #endif
1063 	}
1064 	free(filename);
1065 	return (m);
1066 }
1067 
1068 /*
1069  * Return the size of a file, as cheaply as possible.
1070  * In Unix, we can stat the file.
1071  */
1072 	public POSITION
1073 filesize(f)
1074 	int f;
1075 {
1076 #if HAVE_STAT
1077 	struct stat statbuf;
1078 
1079 	if (fstat(f, &statbuf) >= 0)
1080 		return ((POSITION) statbuf.st_size);
1081 #else
1082 #ifdef _OSK
1083 	long size;
1084 
1085 	if ((size = (long) _gs_size(f)) >= 0)
1086 		return ((POSITION) size);
1087 #endif
1088 #endif
1089 	return (seek_filesize(f));
1090 }
1091 
1092 /*
1093  *
1094  */
1095 	public char *
1096 shell_coption()
1097 {
1098 	return ("-c");
1099 }
1100 
1101 /*
1102  * Return last component of a pathname.
1103  */
1104 	public char *
1105 last_component(name)
1106 	char *name;
1107 {
1108 	char *slash;
1109 
1110 	for (slash = name + strlen(name);  slash > name; )
1111 	{
1112 		--slash;
1113 		if (*slash == *PATHNAME_SEP || *slash == '/')
1114 			return (slash + 1);
1115 	}
1116 	return (name);
1117 }
1118 
1119