xref: /openbsd/usr.bin/less/filename.c (revision 404b540a)
1 /*
2  * Copyright (C) 1984-2002  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 about less, or for information on how to
8  * contact the author, see the README file.
9  */
10 
11 
12 /*
13  * Routines to mess around with filenames (and files).
14  * Much of this is very OS dependent.
15  */
16 
17 #include "less.h"
18 #include "lglob.h"
19 #if MSDOS_COMPILER
20 #include <dos.h>
21 #if MSDOS_COMPILER==WIN32C && !defined(_MSC_VER)
22 #include <dir.h>
23 #endif
24 #if MSDOS_COMPILER==DJGPPC
25 #include <glob.h>
26 #include <dir.h>
27 #define _MAX_PATH	PATH_MAX
28 #endif
29 #endif
30 #ifdef _OSK
31 #include <rbf.h>
32 #ifndef _OSK_MWC32
33 #include <modes.h>
34 #endif
35 #endif
36 #if OS2
37 #include <signal.h>
38 #endif
39 
40 #if HAVE_STAT
41 #include <sys/stat.h>
42 #ifndef S_ISDIR
43 #define	S_ISDIR(m)	(((m) & S_IFMT) == S_IFDIR)
44 #endif
45 #ifndef S_ISREG
46 #define	S_ISREG(m)	(((m) & S_IFMT) == S_IFREG)
47 #endif
48 #endif
49 
50 
51 extern int force_open;
52 extern int secure;
53 extern int use_lessopen;
54 extern IFILE curr_ifile;
55 extern IFILE old_ifile;
56 #if SPACES_IN_FILENAMES
57 extern char openquote;
58 extern char closequote;
59 #endif
60 
61 /*
62  * Remove quotes around a filename.
63  */
64 	public char *
65 shell_unquote(str)
66 	char *str;
67 {
68 	char *name;
69 	char *p;
70 
71 	name = p = (char *) ecalloc(strlen(str)+1, sizeof(char));
72 	if (*str == openquote)
73 	{
74 		str++;
75 		while (*str != '\0')
76 		{
77 			if (*str == closequote)
78 			{
79 				if (str[1] != closequote)
80 					break;
81 				str++;
82 			}
83 			*p++ = *str++;
84 		}
85 	} else
86 	{
87 		char *esc = get_meta_escape();
88 		int esclen = strlen(esc);
89 		while (*str != '\0')
90 		{
91 			if (esclen > 0 && strncmp(str, esc, esclen) == 0)
92 				str += esclen;
93 			*p++ = *str++;
94 		}
95 	}
96 	*p = '\0';
97 	return (name);
98 }
99 
100 /*
101  * Get the shell's escape character.
102  */
103 	public char *
104 get_meta_escape()
105 {
106 	char *s;
107 
108 	s = lgetenv("LESSMETAESCAPE");
109 	if (s == NULL)
110 		s = DEF_METAESCAPE;
111 	return (s);
112 }
113 
114 /*
115  * Get the characters which the shell considers to be "metacharacters".
116  */
117 	static char *
118 metachars()
119 {
120 	static char *mchars = NULL;
121 
122 	if (mchars == NULL)
123 	{
124 		mchars = lgetenv("LESSMETACHARS");
125 		if (mchars == NULL)
126 			mchars = DEF_METACHARS;
127 	}
128 	return (mchars);
129 }
130 
131 /*
132  * Is this a shell metacharacter?
133  */
134 	static int
135 metachar(c)
136 	char c;
137 {
138 	return (strchr(metachars(), c) != NULL);
139 }
140 
141 /*
142  * Insert a backslash before each metacharacter in a string.
143  */
144 	public char *
145 shell_quote(s)
146 	char *s;
147 {
148 	char *p;
149 	char *newstr;
150 	int len;
151 	char *esc = get_meta_escape();
152 	int esclen = strlen(esc);
153 	int use_quotes = 0;
154 	int have_quotes = 0;
155 
156 	/*
157 	 * Determine how big a string we need to allocate.
158 	 */
159 	len = 1; /* Trailing null byte */
160 	for (p = s;  *p != '\0';  p++)
161 	{
162 		len++;
163 		if (*p == openquote || *p == closequote)
164 			have_quotes = 1;
165 		if (metachar(*p))
166 		{
167 			if (esclen == 0)
168 			{
169 				/*
170 				 * We've got a metachar, but this shell
171 				 * doesn't support escape chars.  Use quotes.
172 				 */
173 				use_quotes = 1;
174 			} else
175 			{
176 				/*
177 				 * Allow space for the escape char.
178 				 */
179 				len += esclen;
180 			}
181 		}
182 	}
183 	if (use_quotes)
184 	{
185 		if (have_quotes)
186 			/*
187 			 * We can't quote a string that contains quotes.
188 			 */
189 			return (NULL);
190 		len = strlen(s) + 3;
191 	}
192 	/*
193 	 * Allocate and construct the new string.
194 	 */
195 	newstr = p = (char *) ecalloc(len, sizeof(char));
196 	if (use_quotes)
197 	{
198 		snprintf(newstr, len, "%c%s%c", openquote, s, closequote);
199 	} else
200 	{
201 		while (*s != '\0')
202 		{
203 			if (metachar(*s))
204 			{
205 				/*
206 				 * Add the escape char.
207 				 */
208 				strlcpy(p, esc, newstr + len - p);
209 				p += esclen;
210 			}
211 			*p++ = *s++;
212 		}
213 		*p = '\0';
214 	}
215 	return (newstr);
216 }
217 
218 /*
219  * Return a pathname that points to a specified file in a specified directory.
220  * Return NULL if the file does not exist in the directory.
221  */
222 	static char *
223 dirfile(dirname, filename)
224 	char *dirname;
225 	char *filename;
226 {
227 	char *pathname;
228 	char *qpathname;
229 	int f;
230 	size_t len;
231 
232 	if (dirname == NULL || *dirname == '\0')
233 		return (NULL);
234 	/*
235 	 * Construct the full pathname.
236 	 */
237 	len = strlen(dirname) + strlen(filename) + 2;
238 	pathname = (char *) calloc(len, sizeof(char));
239 	if (pathname == NULL)
240 		return (NULL);
241 	snprintf(pathname, len, "%s%s%s", dirname, PATHNAME_SEP, filename);
242 	/*
243 	 * Make sure the file exists.
244 	 */
245 	qpathname = shell_unquote(pathname);
246 	f = open(qpathname, OPEN_READ);
247 	if (f < 0)
248 	{
249 		free(pathname);
250 		pathname = NULL;
251 	} else
252 	{
253 		close(f);
254 	}
255 	free(qpathname);
256 	return (pathname);
257 }
258 
259 /*
260  * Return the full pathname of the given file in the "home directory".
261  */
262 	public char *
263 homefile(filename)
264 	char *filename;
265 {
266 	register char *pathname;
267 
268 	/*
269 	 * Try $HOME/filename.
270 	 */
271 	pathname = dirfile(lgetenv("HOME"), filename);
272 	if (pathname != NULL)
273 		return (pathname);
274 #if OS2
275 	/*
276 	 * Try $INIT/filename.
277 	 */
278 	pathname = dirfile(lgetenv("INIT"), filename);
279 	if (pathname != NULL)
280 		return (pathname);
281 #endif
282 #if MSDOS_COMPILER || OS2
283 	/*
284 	 * Look for the file anywhere on search path.
285 	 */
286 	pathname = (char *) calloc(_MAX_PATH, sizeof(char));
287 #if MSDOS_COMPILER==DJGPPC
288 	{
289 		char *res = searchpath(filename);
290 		if (res == 0)
291 			*pathname = '\0';
292 		else
293 			strlcpy(pathname, res, _MAX_PATH);
294 	}
295 #else
296 	_searchenv(filename, "PATH", pathname);
297 #endif
298 	if (*pathname != '\0')
299 		return (pathname);
300 	free(pathname);
301 #endif
302 	return (NULL);
303 }
304 
305 #ifdef HELPFILE
306 /*
307  * Find out where the help file is.
308  */
309 	public char *
310 find_helpfile()
311 {
312 	char *helpfile;
313 
314 	if ((helpfile = getenv("LESSHELP")) != NULL && *helpfile != '\0')
315 		return (save(helpfile));
316 #if MSDOS_COMPILER || OS2
317 	return (homefile(HELPFILE));
318 #else
319 	return (save(HELPFILE));
320 #endif
321 }
322 #endif
323 
324 /*
325  * Expand a string, substituting any "%" with the current filename,
326  * and any "#" with the previous filename.
327  * But a string of N "%"s is just replaced with N-1 "%"s.
328  * Likewise for a string of N "#"s.
329  * {{ This is a lot of work just to support % and #. }}
330  */
331 	public char *
332 fexpand(s)
333 	char *s;
334 {
335 	register char *fr, *to;
336 	register int n;
337 	register char *e;
338 	IFILE ifile;
339 
340 #define	fchar_ifile(c) \
341 	((c) == '%' ? curr_ifile : \
342 	 (c) == '#' ? old_ifile : NULL_IFILE)
343 
344 	/*
345 	 * Make one pass to see how big a buffer we
346 	 * need to allocate for the expanded string.
347 	 */
348 	n = 0;
349 	for (fr = s;  *fr != '\0';  fr++)
350 	{
351 		switch (*fr)
352 		{
353 		case '%':
354 		case '#':
355 			if (fr > s && fr[-1] == *fr)
356 			{
357 				/*
358 				 * Second (or later) char in a string
359 				 * of identical chars.  Treat as normal.
360 				 */
361 				n++;
362 			} else if (fr[1] != *fr)
363 			{
364 				/*
365 				 * Single char (not repeated).  Treat specially.
366 				 */
367 				ifile = fchar_ifile(*fr);
368 				if (ifile == NULL_IFILE)
369 					n++;
370 				else
371 					n += strlen(get_filename(ifile));
372 			}
373 			/*
374 			 * Else it is the first char in a string of
375 			 * identical chars.  Just discard it.
376 			 */
377 			break;
378 		default:
379 			n++;
380 			break;
381 		}
382 	}
383 
384 	e = (char *) ecalloc(n+1, sizeof(char));
385 
386 	/*
387 	 * Now copy the string, expanding any "%" or "#".
388 	 */
389 	to = e;
390 	for (fr = s;  *fr != '\0';  fr++)
391 	{
392 		switch (*fr)
393 		{
394 		case '%':
395 		case '#':
396 			if (fr > s && fr[-1] == *fr)
397 			{
398 				*to++ = *fr;
399 			} else if (fr[1] != *fr)
400 			{
401 				ifile = fchar_ifile(*fr);
402 				if (ifile == NULL_IFILE)
403 					*to++ = *fr;
404 				else
405 				{
406 					strlcpy(to, get_filename(ifile),
407 					    e + n + 1 - to);
408 					to += strlen(to);
409 				}
410 			}
411 			break;
412 		default:
413 			*to++ = *fr;
414 			break;
415 		}
416 	}
417 	*to = '\0';
418 	return (e);
419 }
420 
421 #if TAB_COMPLETE_FILENAME
422 
423 /*
424  * Return a blank-separated list of filenames which "complete"
425  * the given string.
426  */
427 	public char *
428 fcomplete(s)
429 	char *s;
430 {
431 	char *fpat;
432 	char *qs;
433 	size_t len;
434 
435 	if (secure)
436 		return (NULL);
437 	/*
438 	 * Complete the filename "s" by globbing "s*".
439 	 */
440 #if MSDOS_COMPILER && (MSDOS_COMPILER == MSOFTC || MSDOS_COMPILER == BORLANDC)
441 	/*
442 	 * But in DOS, we have to glob "s*.*".
443 	 * But if the final component of the filename already has
444 	 * a dot in it, just do "s*".
445 	 * (Thus, "FILE" is globbed as "FILE*.*",
446 	 *  but "FILE.A" is globbed as "FILE.A*").
447 	 */
448 	{
449 		char *slash;
450 		for (slash = s+strlen(s)-1;  slash > s;  slash--)
451 			if (*slash == *PATHNAME_SEP || *slash == '/')
452 				break;
453 		len = strlen(s) + 4;
454 		fpat = (char *) ecalloc(len, sizeof(char));
455 		if (strchr(slash, '.') == NULL)
456 			snprintf(fpat, len, "%s*.*", s);
457 		else
458 			snprintf(fpat, len, "%s*", s);
459 	}
460 #else
461 	len = strlen(s) + 2;
462 	fpat = (char *) ecalloc(len, sizeof(char));
463 	snprintf(fpat, len, "%s*", s);
464 #endif
465 	qs = lglob(fpat);
466 	s = shell_unquote(qs);
467 	if (strcmp(s,fpat) == 0)
468 	{
469 		/*
470 		 * The filename didn't expand.
471 		 */
472 		free(qs);
473 		qs = NULL;
474 	}
475 	free(s);
476 	free(fpat);
477 	return (qs);
478 }
479 #endif
480 
481 /*
482  * Try to determine if a file is "binary".
483  * This is just a guess, and we need not try too hard to make it accurate.
484  */
485 	public int
486 bin_file(f)
487 	int f;
488 {
489 	int i;
490 	int n;
491 	unsigned char data[64];
492 
493 	if (!seekable(f))
494 		return (0);
495 	if (lseek(f, (off_t)0, SEEK_SET) == BAD_LSEEK)
496 		return (0);
497 	n = read(f, data, sizeof(data));
498 	for (i = 0;  i < n;  i++)
499 		if (binary_char(data[i]))
500 			return (1);
501 	return (0);
502 }
503 
504 /*
505  * Try to determine the size of a file by seeking to the end.
506  */
507 	static POSITION
508 seek_filesize(f)
509 	int f;
510 {
511 	off_t spos;
512 
513 	spos = lseek(f, (off_t)0, SEEK_END);
514 	if (spos == BAD_LSEEK)
515 		return (NULL_POSITION);
516 	return ((POSITION) spos);
517 }
518 
519 /*
520  * Read a string from a file.
521  * Return a pointer to the string in memory.
522  */
523 	static char *
524 readfd(fd)
525 	FILE *fd;
526 {
527 	int len;
528 	int ch;
529 	char *buf;
530 	char *p;
531 
532 	/*
533 	 * Make a guess about how many chars in the string
534 	 * and allocate a buffer to hold it.
535 	 */
536 	len = 100;
537 	buf = (char *) ecalloc(len, sizeof(char));
538 	for (p = buf;  ;  p++)
539 	{
540 		if ((ch = getc(fd)) == '\n' || ch == EOF)
541 			break;
542 		if (p - buf >= len-1)
543 		{
544 			/*
545 			 * The string is too big to fit in the buffer we have.
546 			 * Allocate a new buffer, twice as big.
547 			 */
548 			len *= 2;
549 			*p = '\0';
550 			p = (char *) ecalloc(len, sizeof(char));
551 			strlcpy(p, buf, len);
552 			free(buf);
553 			buf = p;
554 			p = buf + strlen(buf);
555 		}
556 		*p = ch;
557 	}
558 	*p = '\0';
559 	return (buf);
560 }
561 
562 
563 
564 #if HAVE_POPEN
565 
566 FILE *popen();
567 
568 /*
569  * Execute a shell command.
570  * Return a pointer to a pipe connected to the shell command's standard output.
571  */
572 	static FILE *
573 shellcmd(cmd)
574 	char *cmd;
575 {
576 	FILE *fd;
577 	size_t len;
578 
579 #if HAVE_SHELL
580 	char *shell;
581 
582 	shell = lgetenv("SHELL");
583 	if (shell != NULL && *shell != '\0')
584 	{
585 		char *scmd;
586 		char *esccmd;
587 
588 		/*
589 		 * Read the output of <$SHELL -c cmd>.
590 		 * Escape any metacharacters in the command.
591 		 */
592 		esccmd = shell_quote(cmd);
593 		if (esccmd == NULL)
594 		{
595 			fd = popen(cmd, "r");
596 		} else
597 		{
598 			len = strlen(shell) + strlen(esccmd) + 5;
599 			scmd = (char *) ecalloc(len, sizeof(char));
600 			snprintf(scmd, len, "%s %s %s", shell, shell_coption(),
601 			    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 /*
623  * Expand a filename, doing any system-specific metacharacter substitutions.
624  */
625 	public char *
626 lglob(filename)
627 	char *filename;
628 {
629 	char *gfilename;
630 	char *ofilename;
631 
632 	ofilename = fexpand(filename);
633 	if (secure)
634 		return (ofilename);
635 	filename = shell_unquote(ofilename);
636 
637 #ifdef DECL_GLOB_LIST
638 {
639 	/*
640 	 * The globbing function returns a list of names.
641 	 */
642 	int length;
643 	char *p;
644 	char *qfilename;
645 	DECL_GLOB_LIST(list)
646 
647 	GLOB_LIST(filename, list);
648 	if (GLOB_LIST_FAILED(list))
649 	{
650 		free(filename);
651 		return (ofilename);
652 	}
653 	length = 1; /* Room for trailing null byte */
654 	for (SCAN_GLOB_LIST(list, p))
655 	{
656 		INIT_GLOB_LIST(list, p);
657 		qfilename = shell_quote(p);
658 		if (qfilename != NULL)
659 		{
660 	  		length += strlen(qfilename) + 1;
661 			free(qfilename);
662 		}
663 	}
664 	gfilename = (char *) ecalloc(length, sizeof(char));
665 	for (SCAN_GLOB_LIST(list, p))
666 	{
667 		INIT_GLOB_LIST(list, p);
668 		qfilename = shell_quote(p);
669 		if (qfilename != NULL)
670 		{
671 			snprintf(gfilename + strlen(gfilename),
672 			    length - strlen(gfilename), "%s ", qfilename);
673 			free(qfilename);
674 		}
675 	}
676 	/*
677 	 * Overwrite the final trailing space with a null terminator.
678 	 */
679 	if (gfilename[0] != '\0' && gfilename[strlen(gfilename) - 1] == ' ')
680 		gfilename[strlen(gfilename) - 1] = '\0';
681 	GLOB_LIST_DONE(list);
682 }
683 #else
684 #ifdef DECL_GLOB_NAME
685 {
686 	/*
687 	 * The globbing function returns a single name, and
688 	 * is called multiple times to walk thru all names.
689 	 */
690 	register char *p;
691 	register int len;
692 	register int n;
693 	char *pathname;
694 	char *qpathname;
695 	DECL_GLOB_NAME(fnd,drive,dir,fname,ext,handle)
696 
697 	GLOB_FIRST_NAME(filename, &fnd, handle);
698 	if (GLOB_FIRST_FAILED(handle))
699 	{
700 		free(filename);
701 		return (ofilename);
702 	}
703 
704 	_splitpath(filename, drive, dir, fname, ext);
705 	len = 100;
706 	gfilename = (char *) ecalloc(len, sizeof(char));
707 	p = gfilename;
708 	do {
709 		n = strlen(drive) + strlen(dir) + strlen(fnd.GLOB_NAME) + 1;
710 		pathname = (char *) ecalloc(n, sizeof(char));
711 		snprintf(pathname, n, "%s%s%s", drive, dir, fnd.GLOB_NAME);
712 		qpathname = shell_quote(pathname);
713 		free(pathname);
714 		if (qpathname != NULL)
715 		{
716 			n = strlen(qpathname);
717 			while (p - gfilename + n + 2 >= len)
718 			{
719 				/*
720 				 * No room in current buffer.
721 				 * Allocate a bigger one.
722 				 */
723 				len *= 2;
724 				*p = '\0';
725 				p = (char *) ecalloc(len, sizeof(char));
726 				strlcpy(p, gfilename, len);
727 				free(gfilename);
728 				gfilename = p;
729 				p = gfilename + strlen(gfilename);
730 			}
731 			strlcpy(p, qpathname, gfilename + len - p);
732 			free(qpathname);
733 			p += n;
734 			*p++ = ' ';
735 		}
736 	} while (GLOB_NEXT_NAME(handle, &fnd) == 0);
737 
738 	/*
739 	 * Overwrite the final trailing space with a null terminator.
740 	 */
741 	*--p = '\0';
742 	GLOB_NAME_DONE(handle);
743 }
744 #else
745 #if HAVE_POPEN
746 {
747 	/*
748 	 * We get the shell to glob the filename for us by passing
749 	 * an "echo" command to the shell and reading its output.
750 	 */
751 	FILE *fd;
752 	char *s;
753 	char *lessecho;
754 	char *cmd;
755 	char *esc;
756 	size_t len;
757 
758 	esc = get_meta_escape();
759 	if (strlen(esc) == 0)
760 		esc = "-";
761 	esc = shell_quote(esc);
762 	if (esc == NULL)
763 	{
764 		free(filename);
765 		return (ofilename);
766 	}
767 	lessecho = lgetenv("LESSECHO");
768 	if (lessecho == NULL || *lessecho == '\0')
769 		lessecho = "lessecho";
770 	/*
771 	 * Invoke lessecho, and read its output (a globbed list of filenames).
772 	 */
773 	len = strlen(lessecho) + strlen(ofilename) + (7*strlen(metachars())) + 24;
774 	cmd = (char *) ecalloc(len, sizeof(char));
775 	snprintf(cmd, len, "%s -p0x%x -d0x%x -e%s ", lessecho, openquote,
776 	    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 
814 /*
815  * See if we should open a "replacement file"
816  * instead of the file we're about to open.
817  */
818 	public char *
819 open_altfile(filename, pf, pfd)
820 	char *filename;
821 	int *pf;
822 	void **pfd;
823 {
824 #if !HAVE_POPEN
825 	return (NULL);
826 #else
827 	char *lessopen;
828 	char *cmd, *cp;
829 	FILE *fd;
830 	size_t i, len;
831 	int found;
832 #if HAVE_FILENO
833 	int returnfd = 0;
834 #endif
835 
836 	if (!use_lessopen || secure)
837 		return (NULL);
838 	ch_ungetchar(-1);
839 	if ((lessopen = lgetenv("LESSOPEN")) == NULL)
840 		return (NULL);
841 	if (strcmp(filename, "-") == 0)
842 		return (NULL);
843 	if (*lessopen == '|')
844 	{
845 		/*
846 		 * If LESSOPEN starts with a |, it indicates
847 		 * a "pipe preprocessor".
848 		 */
849 #if HAVE_FILENO
850 		lessopen++;
851 		returnfd = 1;
852 #else
853 		error("LESSOPEN pipe is not supported", NULL_PARG);
854 		return (NULL);
855 #endif
856 	}
857 
858 	/* strlen(filename) is guaranteed to be > 0 */
859 	len = strlen(lessopen) + strlen(filename);
860 	cmd = (char *) ecalloc(len, sizeof(char));
861 	for (cp = cmd, i = 0, found = 0; i < strlen(lessopen); i++) {
862 		if (!found && lessopen[i] == '%' && lessopen[i + 1] == 's') {
863 			found = 1;
864 			strlcat(cmd, filename, len);
865 			cp += strlen(filename);
866 			i++;
867 		} else
868 			*cp++ = lessopen[i];
869 	}
870 	fd = shellcmd(cmd);
871 	free(cmd);
872 	if (fd == NULL)
873 	{
874 		/*
875 		 * Cannot create the pipe.
876 		 */
877 		return (NULL);
878 	}
879 #if HAVE_FILENO
880 	if (returnfd)
881 	{
882 		int f;
883 		char c;
884 
885 		/*
886 		 * Read one char to see if the pipe will produce any data.
887 		 * If it does, push the char back on the pipe.
888 		 */
889 		f = fileno(fd);
890 		SET_BINARY(f);
891 		if (read(f, &c, 1) != 1)
892 		{
893 			/*
894 			 * Pipe is empty.  This means there is no alt file.
895 			 */
896 			pclose(fd);
897 			return (NULL);
898 		}
899 		ch_ungetchar(c);
900 		*pfd = (void *) fd;
901 		*pf = f;
902 		return (save("-"));
903 	}
904 #endif
905 	cmd = readfd(fd);
906 	pclose(fd);
907 	if (*cmd == '\0')
908 		/*
909 		 * Pipe is empty.  This means there is no alt file.
910 		 */
911 		return (NULL);
912 	return (cmd);
913 #endif /* HAVE_POPEN */
914 }
915 
916 /*
917  * Close a replacement file.
918  */
919 	public void
920 close_altfile(altfilename, filename, pipefd)
921 	char *altfilename;
922 	char *filename;
923 	void *pipefd;
924 {
925 #if HAVE_POPEN
926 	char *lessclose;
927 	FILE *fd;
928 	char *cmd, *cp;
929 	size_t i, len;
930 	int found;
931 
932 	if (secure)
933 		return;
934 	if (pipefd != NULL)
935 	{
936 #if OS2
937 		/*
938 		 * The pclose function of OS/2 emx sometimes fails.
939 		 * Send SIGINT to the piped process before closing it.
940 		 */
941 		kill(((FILE*)pipefd)->_pid, SIGINT);
942 #endif
943 		pclose((FILE*) pipefd);
944 	}
945 	if ((lessclose = lgetenv("LESSCLOSE")) == NULL)
946 	     	return;
947 	/* strlen(filename) is guaranteed to be > 0 */
948 	len = strlen(lessclose) + strlen(filename) + strlen(altfilename);
949 	cmd = (char *) ecalloc(len, sizeof(char));
950 	for (cp = cmd, i = 0, found = 0; i < strlen(lessclose); i++) {
951 		if (found < 2 && lessclose[i] == '%' && lessclose[i + 1] == 's') {
952 			if (++found == 1) {
953 				strlcat(cmd, filename, len);
954 				cp += strlen(filename);
955 			} else {
956 				strlcat(cmd, altfilename, len);
957 				cp += strlen(altfilename);
958 			}
959 			i++;
960 		} else
961 			*cp++ = lessclose[i];
962 	}
963 	fd = shellcmd(cmd);
964 	free(cmd);
965 	if (fd != NULL)
966 		pclose(fd);
967 #endif
968 }
969 
970 /*
971  * Is the specified file a directory?
972  */
973 	public int
974 is_dir(filename)
975 	char *filename;
976 {
977 	int isdir = 0;
978 
979 	filename = shell_unquote(filename);
980 #if HAVE_STAT
981 {
982 	int r;
983 	struct stat statbuf;
984 
985 	r = stat(filename, &statbuf);
986 	isdir = (r >= 0 && S_ISDIR(statbuf.st_mode));
987 }
988 #else
989 #ifdef _OSK
990 {
991 	register int f;
992 
993 	f = open(filename, S_IREAD | S_IFDIR);
994 	if (f >= 0)
995 		close(f);
996 	isdir = (f >= 0);
997 }
998 #endif
999 #endif
1000 	free(filename);
1001 	return (isdir);
1002 }
1003 
1004 /*
1005  * Returns NULL if the file can be opened and
1006  * is an ordinary file, otherwise an error message
1007  * (if it cannot be opened or is a directory, etc.)
1008  */
1009 	public char *
1010 bad_file(filename)
1011 	char *filename;
1012 {
1013 	register char *m = NULL;
1014 	size_t len;
1015 
1016 	filename = shell_unquote(filename);
1017 	if (is_dir(filename))
1018 	{
1019 		static char is_a_dir[] = " is a directory";
1020 
1021 		len = strlen(filename) + sizeof(is_a_dir);
1022 		m = (char *) ecalloc(len, sizeof(char));
1023 		strlcpy(m, filename, len);
1024 		strlcat(m, is_a_dir, len);
1025 	} else
1026 	{
1027 #if HAVE_STAT
1028 		int r;
1029 		struct stat statbuf;
1030 
1031 		r = stat(filename, &statbuf);
1032 		if (r < 0)
1033 		{
1034 			m = errno_message(filename);
1035 		} else if (force_open)
1036 		{
1037 			m = NULL;
1038 		} else if (!S_ISREG(statbuf.st_mode))
1039 		{
1040 			static char not_reg[] = " is not a regular file (use -f to see it)";
1041 			len = strlen(filename) + sizeof(not_reg);
1042 			m = (char *) ecalloc(len, sizeof(char));
1043 			strlcpy(m, filename, len);
1044 			strlcat(m, not_reg, len);
1045 		}
1046 #endif
1047 	}
1048 	free(filename);
1049 	return (m);
1050 }
1051 
1052 /*
1053  * Return the size of a file, as cheaply as possible.
1054  * In Unix, we can stat the file.
1055  */
1056 	public POSITION
1057 filesize(f)
1058 	int f;
1059 {
1060 #if HAVE_STAT
1061 	struct stat statbuf;
1062 
1063 	if (fstat(f, &statbuf) >= 0)
1064 		return ((POSITION) statbuf.st_size);
1065 #else
1066 #ifdef _OSK
1067 	long size;
1068 
1069 	if ((size = (long) _gs_size(f)) >= 0)
1070 		return ((POSITION) size);
1071 #endif
1072 #endif
1073 	return (seek_filesize(f));
1074 }
1075 
1076 /*
1077  *
1078  */
1079 	public char *
1080 shell_coption()
1081 {
1082 	return ("-c");
1083 }
1084