svn commit: r187283 - stable/6/usr.bin/vmstat

[Giorgos Keramidas]

Author: keramida (doc committer)
Date: Thu Jan 15 04:49:40 2009
New Revision: 187283
URL: http://svn.freebsd.org/changeset/base/187283

Log:
  MFC 184645 from /head
  
  Repeat vmstat header after window.rows instead of a hardcoded 20.
  
  Use ioctl() to get the window size in vmstat(8), and force a new
  header to be prepended to the output every time the current window
  size changes.  Change the number of lines before each header to the
  current lines of the terminal when the terminal is resized, so that
  the full terminal length can be used for output lines.

Modified:
  stable/6/usr.bin/vmstat/vmstat.c

Modified: stable/6/usr.bin/vmstat/vmstat.c
==============================================================================
--- stable/6/usr.bin/vmstat/vmstat.c	Thu Jan 15 04:48:06 2009	(r187282)
+++ stable/6/usr.bin/vmstat/vmstat.c	Thu Jan 15 04:49:40 2009	(r187283)
@@ -135,7 +135,10 @@ static devstat_select_mode select_mode;
 
 static struct	vmmeter sum, osum;
 
-static int	winlines = 20;
+#define	VMSTAT_DEFAULT_LINES	20	/* Default number of `winlines'. */
+volatile sig_atomic_t wresized;		/* Tty resized, when non-zero. */
+static int winlines = VMSTAT_DEFAULT_LINES; /* Current number of tty rows. */
+
 static int	aflag;
 static int	nflag;
 static int	Pflag;
@@ -164,6 +167,8 @@ static void	kread(int, void *, size_t);
 static void	kreado(int, void *, size_t, size_t);
 static char    *kgetstr(const char *);
 static void	needhdr(int);
+static void	needresize(int);
+static void	doresize(void);
 static void	printhdr(int, u_long);
 static void	usage(void);
 
@@ -279,8 +284,6 @@ main(int argc, char *argv[])
 		errx(1, "Cannot use -P with crash dumps");
 
 	if (todo & VMSTAT) {
-		struct winsize winsize;
-
 		/*
 		 * Make sure that the userland devstat version matches the
 		 * kernel devstat version.  If not, exit and print a
@@ -291,11 +294,6 @@ main(int argc, char *argv[])
 
 
 		argv = getdrivedata(argv);
-		winsize.ws_row = 0;
-		(void) ioctl(STDOUT_FILENO, TIOCGWINSZ, (char *)&winsize);
-		if (winsize.ws_row > 0)
-			winlines = winsize.ws_row;
-
 	}
 
 #define	BACKWARD_COMPATIBILITY
@@ -591,8 +589,27 @@ dovmstat(unsigned int interval, int reps
 
 	uptime = getuptime();
 	halfuptime = uptime / 2;
+
+	/*
+	 * If the user stops the program (control-Z) and then resumes it,
+	 * print out the header again.
+	 */
 	(void)signal(SIGCONT, needhdr);
 
+	/*
+	 * If our standard output is a tty, then install a SIGWINCH handler
+	 * and set wresized so that our first iteration through the main
+	 * iostat loop will peek at the terminal's current rows to find out
+	 * how many lines can fit in a screenful of output.
+	 */
+	if (isatty(fileno(stdout)) != 0) {
+		wresized = 1;
+		(void)signal(SIGWINCH, needresize);
+	} else {
+		wresized = 0;
+		winlines = VMSTAT_DEFAULT_LINES;
+	}
+
 	if (kd != NULL) {
 		if (namelist[X_STATHZ].n_type != 0 &&
 		    namelist[X_STATHZ].n_value != 0)
@@ -770,7 +787,9 @@ printhdr(int ncpus, u_long cpumask)
 		printf("\n");
 	} else
 		printf(" us sy id\n");
-	hdrcnt = winlines - 2;
+	if (wresized != 0)
+		doresize();
+	hdrcnt = winlines;
 }
 
 /*
@@ -783,6 +802,47 @@ needhdr(int dummy __unused)
 	hdrcnt = 1;
 }
 
+/*
+ * When the terminal is resized, force an update of the maximum number of rows
+ * printed between each header repetition.  Then force a new header to be
+ * prepended to the next output.
+ */
+void
+needresize(int signo)
+{
+
+	wresized = 1;
+	hdrcnt = 1;
+}
+
+/*
+ * Update the global `winlines' count of terminal rows.
+ */
+void
+doresize(void)
+{
+	int status;
+	struct winsize w;
+
+	for (;;) {
+		status = ioctl(fileno(stdout), TIOCGWINSZ, &w);
+		if (status == -1 && errno == EINTR)
+			continue;
+		else if (status == -1)
+			err(1, "ioctl");
+		if (w.ws_row > 3)
+			winlines = w.ws_row - 3;
+		else
+			winlines = VMSTAT_DEFAULT_LINES;
+		break;
+	}
+
+	/*
+	 * Inhibit doresize() calls until we are rescheduled by SIGWINCH.
+	 */
+	wresized = 0;
+}
+
 #ifdef notyet
 static void
 dotimes(void)