Fix various functions testing whether a fd looks like it is pointing to a console.
Converts dirstat aproaches to checking the tail of fd2path.

Reference: /n/sources/patch/applied/isatty
Date: Thu Apr 14 15:30:22 CES 2005

--- /sys/src/cmd/ip/telnet.c	Thu Apr 14 15:26:04 2005
+++ /sys/src/cmd/ip/telnet.c	Thu Apr 14 15:26:01 2005
@@ -504,14 +504,13 @@
 static int
 islikeatty(int fd)
 {
-	Dir *d;
-	int iscons;
+	char buf[64];
 
-	if((d = dirfstat(fd)) == nil)
+	if(fd2path(fd, buf, sizeof buf) != 0)
 		return 0;
-	iscons = (strcmp(d->name, "cons") == 0);
-	free(d);
-	return iscons;
+
+	/* might be /mnt/term/dev/cons */
+	return strlen(buf) >= 9 && strcmp(buf+strlen(buf)-9, "/dev/cons") == 0;
 }
 
 /*
--- /sys/src/cmd/rc/plan9.c	Thu Apr 14 15:26:16 2005
+++ /sys/src/cmd/rc/plan9.c	Thu Apr 14 15:26:13 2005
@@ -561,25 +561,13 @@
 int
 Isatty(int fd)
 {
-	Dir *d1, *d2;
-	int ret;
+	char buf[64];
 
-	d1 = dirfstat(fd);
-	if(d1 == nil)
+	if(fd2path(fd, buf, sizeof buf) != 0)
 		return 0;
-	if(strncmp(d1->name, "ptty", 4)==0){	/* fwd complaints to philw */
-		free(d1);
-		return 1;
-	}
-	d2 = dirstat("/dev/cons");
-	if(d2 == nil){
-		free(d1);
-		return 0;
-	}
-	ret = (d1->type==d2->type&&d1->dev==d2->dev&&d1->qid.path==d2->qid.path);
-	free(d1);
-	free(d2);
-	return ret;
+
+	/* might be /mnt/term/dev/cons */
+	return strlen(buf) >= 9 && strcmp(buf+strlen(buf)-9, "/dev/cons") == 0;
 }
 
 void
--- /sys/src/cmd/upas/common/libsys.c	Thu Apr 14 15:26:32 2005
+++ /sys/src/cmd/upas/common/libsys.c	Thu Apr 14 15:26:29 2005
@@ -706,15 +706,13 @@
 static int
 islikeatty(int fd)
 {
-	Dir *d;
-	int rv;
+	char buf[64];
 
-	d = dirfstat(fd);
-	if(d == nil)
+	if(fd2path(fd, buf, sizeof buf) != 0)
 		return 0;
-	rv = strcmp(d->name, "cons") == 0;
-	free(d);
-	return rv;
+
+	/* might be /mnt/term/dev/cons */
+	return strlen(buf) >= 9 && strcmp(buf+strlen(buf)-9, "/dev/cons") == 0;
 }
 
 extern int
--- /sys/src/libstdio/setvbuf.c	Thu Apr 14 15:26:49 2005
+++ /sys/src/libstdio/setvbuf.c	Thu Apr 14 15:26:47 2005
@@ -40,17 +40,11 @@
 static int
 isatty(int fd)
 {
-	Dir *d1, *d2;
-	int ret;
+	char buf[64];
 
-	d1 = dirfstat(fd);
-	d2 = dirstat("/dev/cons");
-	ret = 0;
-	if(d1!=nil && d2!=nil)
-		ret = (d1->qid.path == d2->qid.path) &&
-			(d1->type == d2->type) &&
-			(d1->dev == d2->dev);
-	free(d1);
-	free(d2);
-	return 0;
+	if(fd2path(fd, buf, sizeof buf) != 0)
+		return 0;
+
+	/* might be /mnt/term/dev/cons */
+	return strlen(buf) >= 9 && strcmp(buf+strlen(buf)-9, "/dev/cons") == 0;
 }