Reimplement ctermid().

Even though POSIX allows us to return simply /dev/tty as a pathname
identifying the controlling terminal of the running process, it is nicer
if this function were actually useful, by returning the actual pathname
of the controlling terminal.

Implement ctermid() by using the kern.devname sysctl to resolve the
actual name of /dev/tty. Don't use devname(3), since it may return bogus
strings like #C:0x123.

2 files changed, 35 insertions, 21 deletions

diff --git a/lib/libc/gen/ctermid.3 b/lib/libc/gen/ctermid.3
index 3402d1d..d737e5e 100644
--- a/lib/libc/gen/ctermid.3
+++ b/lib/libc/gen/ctermid.3
@@ -28,7 +28,7 @@
 .\"     @(#)ctermid.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd June 4, 1993
+.Dd October 1, 2011
 .Dt CTERMID 3
 .Os
 .Sh NAME
@@ -77,7 +77,8 @@ pointer,
 .Dv NULL
 is returned.
 .Pp
-The current implementation simply returns
+If no suitable lookup of the controlling terminal name can be performed,
+this implementation returns
 .Ql /dev/tty .
 .Sh RETURN VALUES
 Upon successful completion, a
diff --git a/lib/libc/gen/ctermid.c b/lib/libc/gen/ctermid.c
index f88b1f5..8af1cb2 100644
--- a/lib/libc/gen/ctermid.c
+++ b/lib/libc/gen/ctermid.c
@@ -1,6 +1,6 @@
 /*-
- * Copyright (c) 1990, 1993
- *	The Regents of the University of California.  All rights reserved.
+ * Copyright (c) 2011 Ed Schouten <ed@FreeBSD.org>
+ * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -10,14 +10,11 @@
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
- * 4. Neither the name of the University nor the names of its contributors
- *    may be used to endorse or promote products derived from this software
- *    without specific prior written permission.
  *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
@@ -27,31 +24,47 @@
  * SUCH DAMAGE.
  */
 
-#if defined(LIBC_SCCS) && !defined(lint)
-static char sccsid[] = "@(#)ctermid.c	8.1 (Berkeley) 6/4/93";
-#endif /* LIBC_SCCS and not lint */
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
-#include <stdio.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <sys/sysctl.h>
+
+#include <errno.h>
 #include <paths.h>
+#include <stdio.h>
 #include <string.h>
 
+#define	LEN_PATH_DEV	(sizeof(_PATH_DEV) - 1)
+
 char *
 ctermid(char *s)
 {
-	static char def[] = _PATH_TTY;
+	static char def[sizeof(_PATH_DEV) + SPECNAMELEN];
+	struct stat sb;
+	size_t dlen;
+	int sverrno;
 
-	if (s) {
-		bcopy(def, s, sizeof(_PATH_TTY));
-		return(s);
-	}
-	return(def);
-}
+	if (s == NULL) {
+		s = def;
+		dlen = sizeof(def) - LEN_PATH_DEV;
+	} else
+		dlen = L_ctermid - LEN_PATH_DEV;
+	strcpy(s, _PATH_TTY);
 
+	/* Attempt to perform a lookup of the actual TTY pathname. */
+	sverrno = errno;
+	if (stat(_PATH_TTY, &sb) == 0 && S_ISCHR(sb.st_mode))
+		(void)sysctlbyname("kern.devname", s + LEN_PATH_DEV,
+		    &dlen, &sb.st_rdev, sizeof(sb.st_rdev));
+	errno = sverrno;
+	return (s);
+}
 
 char *
 ctermid_r(char *s)
 {
-	return (s) ? ctermid(s) : NULL;
+
+	return (s != NULL ? ctermid(s) : NULL);
 }