Add link(1) and unlink(1) as special cases of ln(1) and rm(1)

respectively, in accordance with SUSv2.

This differs from the approach taken in NetBSD, but provides
less obscure error messages in at least the EISDIR case and
does not take up additional disk space for new binaries.

PR:		13071
PR:		13074
Requested by:	James Howard <howardjp@wam.umd.edu>

3 files changed, 42 insertions, 2 deletions

diff --git a/bin/rm/Makefile b/bin/rm/Makefile
index 45a5f23268f1..dcdae17fe0eb 100644
--- a/bin/rm/Makefile
+++ b/bin/rm/Makefile
@@ -4,6 +4,9 @@
 PROG=	rm
 SRCS=   rm.c stat_flags.c
 
+LINKS=	${BINDIR}/rm ${BINDIR}/unlink
+MLINKS=	rm.1 unlink.1
+
 .PATH: ${.CURDIR}/../ls
 
 .include <bsd.prog.mk>
diff --git a/bin/rm/rm.1 b/bin/rm/rm.1
index 0c4b740f1543..a9b04af220dd 100644
--- a/bin/rm/rm.1
+++ b/bin/rm/rm.1
@@ -39,12 +39,15 @@
 .Dt RM 1
 .Os
 .Sh NAME
-.Nm rm
+.Nm rm ,
+.Nm unlink
 .Nd remove directory entries
 .Sh SYNOPSIS
 .Nm rm
 .Op Fl dfiPRrvW
 .Ar file ...
+.Nm unlink
+.Ar file
 .Sh DESCRIPTION
 The
 .Nm
@@ -116,6 +119,16 @@ It is an error to attempt to remove the files
 or
 .Dq .. .
 .Pp
+When the utility is called as
+.Nm unlink ,
+only one argument,
+which must not be a directory,
+may be supplied.
+No options may be supplied in this simple mode of operation,
+which simply performs an
+.Xr unlink 2
+operation using the two passed arguments.
+.Pp
 The
 .Nm
 utility exits 0 if all of the named files or file hierarchies were removed,
@@ -198,3 +211,7 @@ A
 .Nm
 command appeared in
 .At v1 .
+The simplified
+.Nm unlink
+command conforms to
+.St -susv2 .
diff --git a/bin/rm/rm.c b/bin/rm/rm.c
index 7d7de4be2929..a4a3c9676b0e 100644
--- a/bin/rm/rm.c
+++ b/bin/rm/rm.c
@@ -86,6 +86,24 @@ main(argc, argv)
 	char *argv[];
 {
 	int ch, rflag;
+	char *p;
+
+	/*
+	 * Test for the special case where the utility is called as
+	 * "unlink", for which the functionality provided is greatly
+	 * simplified.
+	 */
+	if ((p = rindex(argv[0], '/')) == NULL)
+		p = argv[0];
+	else
+		++p;
+	if (strcmp(p, "unlink") == 0) {
+		if (argc == 2) {
+			rm_file(&argv[1]);
+			exit(eval);
+		} else 
+			usage();
+	}
 
 	Pflag = rflag = 0;
 	while ((ch = getopt(argc, argv, "dfiPRrvW")) != -1)
@@ -472,6 +490,8 @@ void
 usage()
 {
 
-	(void)fprintf(stderr, "usage: rm [-f | -i] [-dPRrvW] file ...\n");
+	(void)fprintf(stderr, "%s\n%s\n",
+	    "usage: rm [-f | -i] [-dPRrvW] file ...",
+	    "       unlink file");
 	exit(EX_USAGE);
 }