xref: /freebsd/contrib/less/filename.c (revision 9a14aa017b21c292740c00ee098195cd46642730)
1 /*
2  * Copyright (C) 1984-2011  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 int ctldisp;
55 extern int utf_mode;
56 extern IFILE curr_ifile;
57 extern IFILE old_ifile;
58 #if SPACES_IN_FILENAMES
59 extern char openquote;
60 extern char closequote;
61 #endif
62 
63 /*
64  * Remove quotes around a filename.
65  */
66 	public char *
67 shell_unquote(str)
68 	char *str;
69 {
70 	char *name;
71 	char *p;
72 
73 	name = p = (char *) ecalloc(strlen(str)+1, sizeof(char));
74 	if (*str == openquote)
75 	{
76 		str++;
77 		while (*str != '\0')
78 		{
79 			if (*str == closequote)
80 			{
81 				if (str[1] != closequote)
82 					break;
83 				str++;
84 			}
85 			*p++ = *str++;
86 		}
87 	} else
88 	{
89 		char *esc = get_meta_escape();
90 		int esclen = strlen(esc);
91 		while (*str != '\0')
92 		{
93 			if (esclen > 0 && strncmp(str, esc, esclen) == 0)
94 				str += esclen;
95 			*p++ = *str++;
96 		}
97 	}
98 	*p = '\0';
99 	return (name);
100 }
101 
102 /*
103  * Get the shell's escape character.
104  */
105 	public char *
106 get_meta_escape()
107 {
108 	char *s;
109 
110 	s = lgetenv("LESSMETAESCAPE");
111 	if (s == NULL)
112 		s = DEF_METAESCAPE;
113 	return (s);
114 }
115 
116 /*
117  * Get the characters which the shell considers to be "metacharacters".
118  */
119 	static char *
120 metachars()
121 {
122 	static char *mchars = NULL;
123 
124 	if (mchars == NULL)
125 	{
126 		mchars = lgetenv("LESSMETACHARS");
127 		if (mchars == NULL)
128 			mchars = DEF_METACHARS;
129 	}
130 	return (mchars);
131 }
132 
133 /*
134  * Is this a shell metacharacter?
135  */
136 	static int
137 metachar(c)
138 	char c;
139 {
140 	return (strchr(metachars(), c) != NULL);
141 }
142 
143 /*
144  * Insert a backslash before each metacharacter in a string.
145  */
146 	public char *
147 shell_quote(s)
148 	char *s;
149 {
150 	char *p;
151 	char *newstr;
152 	int len;
153 	char *esc = get_meta_escape();
154 	int esclen = strlen(esc);
155 	int use_quotes = 0;
156 	int have_quotes = 0;
157 
158 	/*
159 	 * Determine how big a string we need to allocate.
160 	 */
161 	len = 1; /* Trailing null byte */
162 	for (p = s;  *p != '\0';  p++)
163 	{
164 		len++;
165 		if (*p == openquote || *p == closequote)
166 			have_quotes = 1;
167 		if (metachar(*p))
168 		{
169 			if (esclen == 0)
170 			{
171 				/*
172 				 * We've got a metachar, but this shell
173 				 * doesn't support escape chars.  Use quotes.
174 				 */
175 				use_quotes = 1;
176 			} else
177 			{
178 				/*
179 				 * Allow space for the escape char.
180 				 */
181 				len += esclen;
182 			}
183 		}
184 	}
185 	if (use_quotes)
186 	{
187 		if (have_quotes)
188 			/*
189 			 * We can't quote a string that contains quotes.
190 			 */
191 			return (NULL);
192 		len = strlen(s) + 3;
193 	}
194 	/*
195 	 * Allocate and construct the new string.
196 	 */
197 	newstr = p = (char *) ecalloc(len, sizeof(char));
198 	if (use_quotes)
199 	{
200 		SNPRINTF3(newstr, len, "%c%s%c", openquote, s, closequote);
201 	} else
202 	{
203 		while (*s != '\0')
204 		{
205 			if (metachar(*s))
206 			{
207 				/*
208 				 * Add the escape char.
209 				 */
210 				strcpy(p, esc);
211 				p += esclen;
212 			}
213 			*p++ = *s++;
214 		}
215 		*p = '\0';
216 	}
217 	return (newstr);
218 }
219 
220 /*
221  * Return a pathname that points to a specified file in a specified directory.
222  * Return NULL if the file does not exist in the directory.
223  */
224 	static char *
225 dirfile(dirname, filename)
226 	char *dirname;
227 	char *filename;
228 {
229 	char *pathname;
230 	char *qpathname;
231 	int len;
232 	int f;
233 
234 	if (dirname == NULL || *dirname == '\0')
235 		return (NULL);
236 	/*
237 	 * Construct the full pathname.
238 	 */
239 	len= strlen(dirname) + strlen(filename) + 2;
240 	pathname = (char *) calloc(len, sizeof(char));
241 	if (pathname == NULL)
242 		return (NULL);
243 	SNPRINTF3(pathname, len, "%s%s%s", dirname, PATHNAME_SEP, filename);
244 	/*
245 	 * Make sure the file exists.
246 	 */
247 	qpathname = shell_unquote(pathname);
248 	f = open(qpathname, OPEN_READ);
249 	if (f < 0)
250 	{
251 		free(pathname);
252 		pathname = NULL;
253 	} else
254 	{
255 		close(f);
256 	}
257 	free(qpathname);
258 	return (pathname);
259 }
260 
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 			strcpy(pathname, res);
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 
307 /*
308  * Expand a string, substituting any "%" with the current filename,
309  * and any "#" with the previous filename.
310  * But a string of N "%"s is just replaced with N-1 "%"s.
311  * Likewise for a string of N "#"s.
312  * {{ This is a lot of work just to support % and #. }}
313  */
314 	public char *
315 fexpand(s)
316 	char *s;
317 {
318 	register char *fr, *to;
319 	register int n;
320 	register char *e;
321 	IFILE ifile;
322 
323 #define	fchar_ifile(c) \
324 	((c) == '%' ? curr_ifile : \
325 	 (c) == '#' ? old_ifile : NULL_IFILE)
326 
327 	/*
328 	 * Make one pass to see how big a buffer we
329 	 * need to allocate for the expanded string.
330 	 */
331 	n = 0;
332 	for (fr = s;  *fr != '\0';  fr++)
333 	{
334 		switch (*fr)
335 		{
336 		case '%':
337 		case '#':
338 			if (fr > s && fr[-1] == *fr)
339 			{
340 				/*
341 				 * Second (or later) char in a string
342 				 * of identical chars.  Treat as normal.
343 				 */
344 				n++;
345 			} else if (fr[1] != *fr)
346 			{
347 				/*
348 				 * Single char (not repeated).  Treat specially.
349 				 */
350 				ifile = fchar_ifile(*fr);
351 				if (ifile == NULL_IFILE)
352 					n++;
353 				else
354 					n += strlen(get_filename(ifile));
355 			}
356 			/*
357 			 * Else it is the first char in a string of
358 			 * identical chars.  Just discard it.
359 			 */
360 			break;
361 		default:
362 			n++;
363 			break;
364 		}
365 	}
366 
367 	e = (char *) ecalloc(n+1, sizeof(char));
368 
369 	/*
370 	 * Now copy the string, expanding any "%" or "#".
371 	 */
372 	to = e;
373 	for (fr = s;  *fr != '\0';  fr++)
374 	{
375 		switch (*fr)
376 		{
377 		case '%':
378 		case '#':
379 			if (fr > s && fr[-1] == *fr)
380 			{
381 				*to++ = *fr;
382 			} else if (fr[1] != *fr)
383 			{
384 				ifile = fchar_ifile(*fr);
385 				if (ifile == NULL_IFILE)
386 					*to++ = *fr;
387 				else
388 				{
389 					strcpy(to, get_filename(ifile));
390 					to += strlen(to);
391 				}
392 			}
393 			break;
394 		default:
395 			*to++ = *fr;
396 			break;
397 		}
398 	}
399 	*to = '\0';
400 	return (e);
401 }
402 
403 
404 #if TAB_COMPLETE_FILENAME
405 
406 /*
407  * Return a blank-separated list of filenames which "complete"
408  * the given string.
409  */
410 	public char *
411 fcomplete(s)
412 	char *s;
413 {
414 	char *fpat;
415 	char *qs;
416 
417 	if (secure)
418 		return (NULL);
419 	/*
420 	 * Complete the filename "s" by globbing "s*".
421 	 */
422 #if MSDOS_COMPILER && (MSDOS_COMPILER == MSOFTC || MSDOS_COMPILER == BORLANDC)
423 	/*
424 	 * But in DOS, we have to glob "s*.*".
425 	 * But if the final component of the filename already has
426 	 * a dot in it, just do "s*".
427 	 * (Thus, "FILE" is globbed as "FILE*.*",
428 	 *  but "FILE.A" is globbed as "FILE.A*").
429 	 */
430 	{
431 		char *slash;
432 		int len;
433 		for (slash = s+strlen(s)-1;  slash > s;  slash--)
434 			if (*slash == *PATHNAME_SEP || *slash == '/')
435 				break;
436 		len = strlen(s) + 4;
437 		fpat = (char *) ecalloc(len, sizeof(char));
438 		if (strchr(slash, '.') == NULL)
439 			SNPRINTF1(fpat, len, "%s*.*", s);
440 		else
441 			SNPRINTF1(fpat, len, "%s*", s);
442 	}
443 #else
444 	{
445 	int len = strlen(s) + 2;
446 	fpat = (char *) ecalloc(len, sizeof(char));
447 	SNPRINTF1(fpat, len, "%s*", s);
448 	}
449 #endif
450 	qs = lglob(fpat);
451 	s = shell_unquote(qs);
452 	if (strcmp(s,fpat) == 0)
453 	{
454 		/*
455 		 * The filename didn't expand.
456 		 */
457 		free(qs);
458 		qs = NULL;
459 	}
460 	free(s);
461 	free(fpat);
462 	return (qs);
463 }
464 #endif
465 
466 /*
467  * Try to determine if a file is "binary".
468  * This is just a guess, and we need not try too hard to make it accurate.
469  */
470 	public int
471 bin_file(f)
472 	int f;
473 {
474 	int n;
475 	int bin_count = 0;
476 	char data[256];
477 	char* p;
478 	char* pend;
479 
480 	if (!seekable(f))
481 		return (0);
482 	if (lseek(f, (off_t)0, SEEK_SET) == BAD_LSEEK)
483 		return (0);
484 	n = read(f, data, sizeof(data));
485 	pend = &data[n];
486 	for (p = data;  p < pend;  )
487 	{
488 		LWCHAR c = step_char(&p, +1, pend);
489 		if (ctldisp == OPT_ONPLUS && IS_CSI_START(c))
490 		{
491 			do {
492 				c = step_char(&p, +1, pend);
493 			} while (p < pend && is_ansi_middle(c));
494 		} else if (binary_char(c))
495 			bin_count++;
496 	}
497 	/*
498 	 * Call it a binary file if there are more than 5 binary characters
499 	 * in the first 256 bytes of the file.
500 	 */
501 	return (bin_count > 5);
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 			strcpy(p, buf);
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 
578 #if HAVE_SHELL
579 	char *shell;
580 
581 	shell = lgetenv("SHELL");
582 	if (shell != NULL && *shell != '\0')
583 	{
584 		char *scmd;
585 		char *esccmd;
586 
587 		/*
588 		 * Read the output of <$SHELL -c cmd>.
589 		 * Escape any metacharacters in the command.
590 		 */
591 		esccmd = shell_quote(cmd);
592 		if (esccmd == NULL)
593 		{
594 			fd = popen(cmd, "r");
595 		} else
596 		{
597 			int len = strlen(shell) + strlen(esccmd) + 5;
598 			scmd = (char *) ecalloc(len, sizeof(char));
599 			SNPRINTF3(scmd, len, "%s %s %s", shell, shell_coption(), esccmd);
600 			free(esccmd);
601 			fd = popen(scmd, "r");
602 			free(scmd);
603 		}
604 	} else
605 #endif
606 	{
607 		fd = popen(cmd, "r");
608 	}
609 	/*
610 	 * Redirection in `popen' might have messed with the
611 	 * standard devices.  Restore binary input mode.
612 	 */
613 	SET_BINARY(0);
614 	return (fd);
615 }
616 
617 #endif /* HAVE_POPEN */
618 
619 
620 /*
621  * Expand a filename, doing any system-specific metacharacter substitutions.
622  */
623 	public char *
624 lglob(filename)
625 	char *filename;
626 {
627 	char *gfilename;
628 	char *ofilename;
629 
630 	ofilename = fexpand(filename);
631 	if (secure)
632 		return (ofilename);
633 	filename = shell_unquote(ofilename);
634 
635 #ifdef DECL_GLOB_LIST
636 {
637 	/*
638 	 * The globbing function returns a list of names.
639 	 */
640 	int length;
641 	char *p;
642 	char *qfilename;
643 	DECL_GLOB_LIST(list)
644 
645 	GLOB_LIST(filename, list);
646 	if (GLOB_LIST_FAILED(list))
647 	{
648 		free(filename);
649 		return (ofilename);
650 	}
651 	length = 1; /* Room for trailing null byte */
652 	for (SCAN_GLOB_LIST(list, p))
653 	{
654 		INIT_GLOB_LIST(list, p);
655 		qfilename = shell_quote(p);
656 		if (qfilename != NULL)
657 		{
658 	  		length += strlen(qfilename) + 1;
659 			free(qfilename);
660 		}
661 	}
662 	gfilename = (char *) ecalloc(length, sizeof(char));
663 	for (SCAN_GLOB_LIST(list, p))
664 	{
665 		INIT_GLOB_LIST(list, p);
666 		qfilename = shell_quote(p);
667 		if (qfilename != NULL)
668 		{
669 			sprintf(gfilename + strlen(gfilename), "%s ", qfilename);
670 			free(qfilename);
671 		}
672 	}
673 	/*
674 	 * Overwrite the final trailing space with a null terminator.
675 	 */
676 	*--p = '\0';
677 	GLOB_LIST_DONE(list);
678 }
679 #else
680 #ifdef DECL_GLOB_NAME
681 {
682 	/*
683 	 * The globbing function returns a single name, and
684 	 * is called multiple times to walk thru all names.
685 	 */
686 	register char *p;
687 	register int len;
688 	register int n;
689 	char *pathname;
690 	char *qpathname;
691 	DECL_GLOB_NAME(fnd,drive,dir,fname,ext,handle)
692 
693 	GLOB_FIRST_NAME(filename, &fnd, handle);
694 	if (GLOB_FIRST_FAILED(handle))
695 	{
696 		free(filename);
697 		return (ofilename);
698 	}
699 
700 	_splitpath(filename, drive, dir, fname, ext);
701 	len = 100;
702 	gfilename = (char *) ecalloc(len, sizeof(char));
703 	p = gfilename;
704 	do {
705 		n = strlen(drive) + strlen(dir) + strlen(fnd.GLOB_NAME) + 1;
706 		pathname = (char *) ecalloc(n, sizeof(char));
707 		SNPRINTF3(pathname, n, "%s%s%s", drive, dir, fnd.GLOB_NAME);
708 		qpathname = shell_quote(pathname);
709 		free(pathname);
710 		if (qpathname != NULL)
711 		{
712 			n = strlen(qpathname);
713 			while (p - gfilename + n + 2 >= len)
714 			{
715 				/*
716 				 * No room in current buffer.
717 				 * Allocate a bigger one.
718 				 */
719 				len *= 2;
720 				*p = '\0';
721 				p = (char *) ecalloc(len, sizeof(char));
722 				strcpy(p, gfilename);
723 				free(gfilename);
724 				gfilename = p;
725 				p = gfilename + strlen(gfilename);
726 			}
727 			strcpy(p, qpathname);
728 			free(qpathname);
729 			p += n;
730 			*p++ = ' ';
731 		}
732 	} while (GLOB_NEXT_NAME(handle, &fnd) == 0);
733 
734 	/*
735 	 * Overwrite the final trailing space with a null terminator.
736 	 */
737 	*--p = '\0';
738 	GLOB_NAME_DONE(handle);
739 }
740 #else
741 #if HAVE_POPEN
742 {
743 	/*
744 	 * We get the shell to glob the filename for us by passing
745 	 * an "echo" command to the shell and reading its output.
746 	 */
747 	FILE *fd;
748 	char *s;
749 	char *lessecho;
750 	char *cmd;
751 	char *esc;
752 	int len;
753 
754 	esc = get_meta_escape();
755 	if (strlen(esc) == 0)
756 		esc = "-";
757 	esc = shell_quote(esc);
758 	if (esc == NULL)
759 	{
760 		free(filename);
761 		return (ofilename);
762 	}
763 	lessecho = lgetenv("LESSECHO");
764 	if (lessecho == NULL || *lessecho == '\0')
765 		lessecho = "lessecho";
766 	/*
767 	 * Invoke lessecho, and read its output (a globbed list of filenames).
768 	 */
769 	len = strlen(lessecho) + strlen(ofilename) + (7*strlen(metachars())) + 24;
770 	cmd = (char *) ecalloc(len, sizeof(char));
771 	SNPRINTF4(cmd, len, "%s -p0x%x -d0x%x -e%s ", lessecho, openquote, closequote, esc);
772 	free(esc);
773 	for (s = metachars();  *s != '\0';  s++)
774 		sprintf(cmd + strlen(cmd), "-n0x%x ", *s);
775 	sprintf(cmd + strlen(cmd), "-- %s", ofilename);
776 	fd = shellcmd(cmd);
777 	free(cmd);
778 	if (fd == NULL)
779 	{
780 		/*
781 		 * Cannot create the pipe.
782 		 * Just return the original (fexpanded) filename.
783 		 */
784 		free(filename);
785 		return (ofilename);
786 	}
787 	gfilename = readfd(fd);
788 	pclose(fd);
789 	if (*gfilename == '\0')
790 	{
791 		free(gfilename);
792 		free(filename);
793 		return (ofilename);
794 	}
795 }
796 #else
797 	/*
798 	 * No globbing functions at all.  Just use the fexpanded filename.
799 	 */
800 	gfilename = save(filename);
801 #endif
802 #endif
803 #endif
804 	free(filename);
805 	free(ofilename);
806 	return (gfilename);
807 }
808 
809 /*
810  * See if we should open a "replacement file"
811  * instead of the file we're about to open.
812  */
813 	public char *
814 open_altfile(filename, pf, pfd)
815 	char *filename;
816 	int *pf;
817 	void **pfd;
818 {
819 #if !HAVE_POPEN
820 	return (NULL);
821 #else
822 	char *lessopen;
823 	char *cmd;
824 	int len;
825 	FILE *fd;
826 #if HAVE_FILENO
827 	int returnfd = 0;
828 #endif
829 
830 	if (!use_lessopen || secure)
831 		return (NULL);
832 	ch_ungetchar(-1);
833 	if ((lessopen = lgetenv("LESSOPEN")) == NULL)
834 		return (NULL);
835 	if (*lessopen == '|')
836 	{
837 		/*
838 		 * If LESSOPEN starts with a |, it indicates
839 		 * a "pipe preprocessor".
840 		 */
841 #if !HAVE_FILENO
842 		error("LESSOPEN pipe is not supported", NULL_PARG);
843 		return (NULL);
844 #else
845 		lessopen++;
846 		returnfd = 1;
847 #endif
848 	}
849 	if (*lessopen == '-') {
850 		/*
851 		 * Lessopen preprocessor will accept "-" as a filename.
852 		 */
853 		lessopen++;
854 	} else {
855 		if (strcmp(filename, "-") == 0)
856 			return (NULL);
857 	}
858 
859 	len = strlen(lessopen) + strlen(filename) + 2;
860 	cmd = (char *) ecalloc(len, sizeof(char));
861 	SNPRINTF1(cmd, len, lessopen, filename);
862 	fd = shellcmd(cmd);
863 	free(cmd);
864 	if (fd == NULL)
865 	{
866 		/*
867 		 * Cannot create the pipe.
868 		 */
869 		return (NULL);
870 	}
871 #if HAVE_FILENO
872 	if (returnfd)
873 	{
874 		int f;
875 		char c;
876 
877 		/*
878 		 * Read one char to see if the pipe will produce any data.
879 		 * If it does, push the char back on the pipe.
880 		 */
881 		f = fileno(fd);
882 		SET_BINARY(f);
883 		if (read(f, &c, 1) != 1)
884 		{
885 			/*
886 			 * Pipe is empty.  This means there is no alt file.
887 			 */
888 			pclose(fd);
889 			return (NULL);
890 		}
891 		ch_ungetchar(c);
892 		*pfd = (void *) fd;
893 		*pf = f;
894 		return (save("-"));
895 	}
896 #endif
897 	cmd = readfd(fd);
898 	pclose(fd);
899 	if (*cmd == '\0')
900 		/*
901 		 * Pipe is empty.  This means there is no alt file.
902 		 */
903 		return (NULL);
904 	return (cmd);
905 #endif /* HAVE_POPEN */
906 }
907 
908 /*
909  * Close a replacement file.
910  */
911 	public void
912 close_altfile(altfilename, filename, pipefd)
913 	char *altfilename;
914 	char *filename;
915 	void *pipefd;
916 {
917 #if HAVE_POPEN
918 	char *lessclose;
919 	FILE *fd;
920 	char *cmd;
921 	int len;
922 
923 	if (secure)
924 		return;
925 	if (pipefd != NULL)
926 	{
927 #if OS2
928 		/*
929 		 * The pclose function of OS/2 emx sometimes fails.
930 		 * Send SIGINT to the piped process before closing it.
931 		 */
932 		kill(((FILE*)pipefd)->_pid, SIGINT);
933 #endif
934 		pclose((FILE*) pipefd);
935 	}
936 	if ((lessclose = lgetenv("LESSCLOSE")) == NULL)
937 	     	return;
938 	len = strlen(lessclose) + strlen(filename) + strlen(altfilename) + 2;
939 	cmd = (char *) ecalloc(len, sizeof(char));
940 	SNPRINTF2(cmd, len, lessclose, filename, altfilename);
941 	fd = shellcmd(cmd);
942 	free(cmd);
943 	if (fd != NULL)
944 		pclose(fd);
945 #endif
946 }
947 
948 /*
949  * Is the specified file a directory?
950  */
951 	public int
952 is_dir(filename)
953 	char *filename;
954 {
955 	int isdir = 0;
956 
957 	filename = shell_unquote(filename);
958 #if HAVE_STAT
959 {
960 	int r;
961 	struct stat statbuf;
962 
963 	r = stat(filename, &statbuf);
964 	isdir = (r >= 0 && S_ISDIR(statbuf.st_mode));
965 }
966 #else
967 #ifdef _OSK
968 {
969 	register int f;
970 
971 	f = open(filename, S_IREAD | S_IFDIR);
972 	if (f >= 0)
973 		close(f);
974 	isdir = (f >= 0);
975 }
976 #endif
977 #endif
978 	free(filename);
979 	return (isdir);
980 }
981 
982 /*
983  * Returns NULL if the file can be opened and
984  * is an ordinary file, otherwise an error message
985  * (if it cannot be opened or is a directory, etc.)
986  */
987 	public char *
988 bad_file(filename)
989 	char *filename;
990 {
991 	register char *m = NULL;
992 
993 	filename = shell_unquote(filename);
994 	if (!force_open && is_dir(filename))
995 	{
996 		static char is_a_dir[] = " is a directory";
997 
998 		m = (char *) ecalloc(strlen(filename) + sizeof(is_a_dir),
999 			sizeof(char));
1000 		strcpy(m, filename);
1001 		strcat(m, is_a_dir);
1002 	} else
1003 	{
1004 #if HAVE_STAT
1005 		int r;
1006 		struct stat statbuf;
1007 
1008 		r = stat(filename, &statbuf);
1009 		if (r < 0)
1010 		{
1011 			m = errno_message(filename);
1012 		} else if (force_open)
1013 		{
1014 			m = NULL;
1015 		} else if (!S_ISREG(statbuf.st_mode))
1016 		{
1017 			static char not_reg[] = " is not a regular file (use -f to see it)";
1018 			m = (char *) ecalloc(strlen(filename) + sizeof(not_reg),
1019 				sizeof(char));
1020 			strcpy(m, filename);
1021 			strcat(m, not_reg);
1022 		}
1023 #endif
1024 	}
1025 	free(filename);
1026 	return (m);
1027 }
1028 
1029 /*
1030  * Return the size of a file, as cheaply as possible.
1031  * In Unix, we can stat the file.
1032  */
1033 	public POSITION
1034 filesize(f)
1035 	int f;
1036 {
1037 #if HAVE_STAT
1038 	struct stat statbuf;
1039 
1040 	if (fstat(f, &statbuf) >= 0)
1041 		return ((POSITION) statbuf.st_size);
1042 #else
1043 #ifdef _OSK
1044 	long size;
1045 
1046 	if ((size = (long) _gs_size(f)) >= 0)
1047 		return ((POSITION) size);
1048 #endif
1049 #endif
1050 	return (seek_filesize(f));
1051 }
1052 
1053 /*
1054  *
1055  */
1056 	public char *
1057 shell_coption()
1058 {
1059 	return ("-c");
1060 }
1061 
1062 /*
1063  * Return last component of a pathname.
1064  */
1065 	public char *
1066 last_component(name)
1067 	char *name;
1068 {
1069 	char *slash;
1070 
1071 	for (slash = name + strlen(name);  slash > name; )
1072 	{
1073 		--slash;
1074 		if (*slash == *PATHNAME_SEP || *slash == '/')
1075 			return (slash + 1);
1076 	}
1077 	return (name);
1078 }
1079 
1080