- Add setfstab() and getfstab().

- Use the environment variable 'PATH_FSTAB' if set rather than the
  hardcoded '/etc/fstab' (fstab.h:_PATH_FSTAB)

include/fstab.h

@@ -75,6 +75,8 @@ struct fstab *getfsspec(const char *);
 struct fstab *getfsfile(const char *);
 int setfsent(void);
 void endfsent(void);
+void setfstab(const char *);
+const char *getfstab(void);
 __END_DECLS
 
 #endif /* !_FSTAB_H_ */

lib/libc/gen/Makefile.inc

@@ -84,7 +84,8 @@ MLINKS+=getcwd.3 getwd.3
 MLINKS+=getcontext.3 setcontext.3
 MLINKS+=getdomainname.3 setdomainname.3
 MLINKS+=getfsent.3 endfsent.3 getfsent.3 getfsfile.3 getfsent.3 getfsspec.3 \
-	getfsent.3 getfstype.3 getfsent.3 setfsent.3
+	getfsent.3 getfstype.3 getfsent.3 setfsent.3 \
+	getfsent.3 setfstab.3 getfsent.3 getfstab.3
 MLINKS+=getgrent.3 endgrent.3 getgrent.3 getgrgid.3 getgrent.3 getgrnam.3 \
 	getgrent.3 setgrent.3 getgrent.3 setgroupent.3
 MLINKS+=gethostname.3 sethostname.3

lib/libc/gen/fstab.c

@@ -54,11 +54,40 @@ __FBSDID("$FreeBSD$");
 static FILE *_fs_fp;
 static struct fstab _fs_fstab;
 static int LineNo = 0;
+static char *path_fstab;
+static char fstab_path[PATH_MAX];
+static int fsp_set = 0;
 
 static void error(int);
 static void fixfsfile(void);
 static int fstabscan(void);
 
+void
+setfstab(const char *file)
+{
+
+	if (file == NULL) {
+		path_fstab = _PATH_FSTAB;
+	} else {
+		strncpy(fstab_path, file, PATH_MAX);
+		fstab_path[PATH_MAX - 1] = '\0';
+		path_fstab = fstab_path;
+	}
+	fsp_set = 1;
+
+	return;
+}
+
+const char *
+getfstab (void)
+{
+
+	if (fsp_set)
+		return (path_fstab);
+	else
+		return (_PATH_FSTAB);
+}
+
 static void
 fixfsfile()
 {
@@ -226,7 +255,13 @@ setfsent()
 		LineNo = 0;
 		return(1);
 	}
-	if ((_fs_fp = fopen(_PATH_FSTAB, "r")) != NULL) {
+	if (fsp_set == 0) {
+		if (issetugid())
+			setfstab(NULL);
+		else
+			setfstab(getenv("PATH_FSTAB"));
+	}
+	if ((_fs_fp = fopen(path_fstab, "r")) != NULL) {
 		LineNo = 0;
 		return(1);
 	}
@@ -241,6 +276,8 @@ endfsent()
 		(void)fclose(_fs_fp);
 		_fs_fp = NULL;
 	}
+
+	fsp_set = 0;
 }
 
 static void
@@ -251,7 +288,7 @@ error(err)
 	char num[30];
 
 	(void)_write(STDERR_FILENO, "fstab: ", 7);
-	(void)_write(STDERR_FILENO, _PATH_FSTAB, sizeof(_PATH_FSTAB) - 1);
+	(void)_write(STDERR_FILENO, path_fstab, strlen(path_fstab));
 	(void)_write(STDERR_FILENO, ":", 1);
 	sprintf(num, "%d: ", LineNo);
 	(void)_write(STDERR_FILENO, num, strlen(num));

lib/libc/gen/getfsent.3

@@ -56,6 +56,10 @@
 .Fn setfsent void
 .Ft void
 .Fn endfsent void
+.Ft void
+.Fn setfstab "const char *file"
+.Ft const char *
+.Fn getfstab void
 .Sh DESCRIPTION
 The
 .Fn getfsent ,
@@ -94,6 +98,18 @@ function
 closes the file.
 .Pp
 The
+.Fn setfstab
+function sets the file to be used by subsequent operations.
+The value set by
+.Fn setfstab
+does not persist across calls to
+.Fn endfsent
+.Pp
+The
+.Fn getfstab
+function returns the name of the file that that will be used.
+.Pp
+The
 .Fn getfsspec
 and
 .Fn getfsfile
@@ -128,6 +144,13 @@ The
 .Fn endfsent
 function
 returns nothing.
+.Sh ENVIRONMENT
+.Bl -tag -width PATH_FSTAB
+.It Pa PATH_FSTAB
+If the environment variable
+.Pa PATH_FSTAB
+is set all operations are performed against the specified file.
+.El
 .Sh FILES
 .Bl -tag -width /etc/fstab -compact
 .It Pa /etc/fstab
@@ -146,7 +169,13 @@ the
 and
 .Fn setfsent
 functions appeared in
-.Bx 4.3 .
+.Bx 4.3 ;
+the
+.Fn setfstab
+and
+.Fn getfstab
+functions appeared in
+.Fx 5.1.
 .Sh BUGS
 These functions use static data storage;
 if the data is needed for future use, it should be