RFC: Port of NetBSD cat(1)'s -f option.

Here's a patch that adds to our cat(1) the same functionality as
NetBSD cat(1) when passed -f on the command line.  The original
commit log from NetBSD's CVS tree is:

	----------------------------
	revision 1.18
	date: 2000/01/15 01:13:15;  author: christos;  state: Exp;  lines: +4 -2
	branches:  1.18.4;
	Add a -f fflag that makes sure that we only try to read from plain files
	so that there is no chance to block.

What do you all think of this?

%%%
Index: cat.1
===================================================================
RCS file: /home/ncvs/src/bin/cat/cat.1,v
retrieving revision 1.19
diff -u -r1.19 cat.1
--- cat.1	25 Sep 2001 18:10:18 -0000	1.19
+++ cat.1	15 May 2002 05:57:28 -0000
@@ -82,6 +82,8 @@
 option), and display a dollar sign
 .Pq Ql \&$
 at the end of each line.
+.It Fl f
+Only attempt to display regular files.
 .It Fl n
 Number the output lines, starting at 1.
 .It Fl s
Index: cat.c
===================================================================
RCS file: /home/ncvs/src/bin/cat/cat.c,v
retrieving revision 1.21
diff -u -r1.21 cat.c
--- cat.c	22 Feb 2002 20:42:57 -0000	1.21
+++ cat.c	15 May 2002 05:56:26 -0000
@@ -66,7 +66,7 @@
 #include <unistd.h>
 #include <stddef.h>
 
-int bflag, eflag, nflag, sflag, tflag, vflag;
+int bflag, eflag, fflag, nflag, sflag, tflag, vflag;
 int rval;
 const char *filename;
 
@@ -85,7 +85,7 @@
 
 	setlocale(LC_CTYPE, "");
 
-	while ((ch = getopt(argc, argv, "benstuv")) != -1)
+	while ((ch = getopt(argc, argv, "befnstuv")) != -1)
 		switch (ch) {
 		case 'b':
 			bflag = nflag = 1;	/* -b implies -n */
@@ -93,6 +93,9 @@
 		case 'e':
 			eflag = vflag = 1;	/* -e implies -v */
 			break;
+		case 'f':
+			fflag = 1;
+			break;
 		case 'n':
 			nflag = 1;
 			break;
@@ -110,12 +113,12 @@
 			break;
 		default:
 			fprintf(stderr,
-			    "usage: cat [-benstuv] [-] [file ...]\n");
+			    "usage: cat [-befnstuv] [-] [file ...]\n");
 			exit(1);
 		}
 	argv += optind;
 
-	if (bflag || eflag || nflag || sflag || tflag || vflag)
+	if (bflag || eflag || fflag || nflag || sflag || tflag || vflag)
 		scanfiles(argv, 1);
 	else
 		scanfiles(argv, 0);
@@ -138,7 +141,15 @@
 			filename = "stdin";
 			fd = STDIN_FILENO;
 		} else {
+			struct stat st;
+
 			filename = path;
+			if (stat(path, &st) < 0 ||
+			    S_ISREG(st.st_mode) == 0) {
+				i++;		/* Skip to next file. */
+				continue;
+			}
+
 			fd = open(path, O_RDONLY);
 #ifndef NO_UDOM_SUPPORT
 			if (fd < 0 && errno == EOPNOTSUPP)
%%%

-- 
Giorgos Keramidas    - http://www.FreeBSD.org
[email protected] - The Power to Serve

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