Attached is a slightly-reworked version of the earlier patch that adds
stderr handling to watch. This version makes the stderr handling
default rather than optional. I prefer this version of the patch,
because of the principle of least surprise in UI design, reference
http://en.wikipedia.org/wiki/Principle_of_least_astonishment . When
one runs a command like "watch ls -ld some_file", and then some_file
is deleted, one is not expecting a bunch of scrolling errors to
obscure the watch command.
I see at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=225549 that
Justin Pryzby thinks dup2(STDOUT_FILENO, STDERR_FILENO) is a bad idea
because it loses the ability to discard stderr. Note that it's still
possible for users to override the default handling inside the
command, i.e.:
watch "ls -ld no_such_file 2>/dev/null"
So anyone who wants to discard stderr still can. And if the desire to
add "discard stderr" as a native watch capability comes up, it's still
possible to add a "discard stderr" option even with the default of
dup2(1, 2). I'd be happy to do this if a "discard stderr" option is
needed for this functionality to be added to watch.
- Morty
diff -Nur procps-3.2.7.orig/watch.1 procps-3.2.7/watch.1
--- procps-3.2.7.orig/watch.1 2003-02-09 02:05:25.000000000 -0500
+++ procps-3.2.7/watch.1 2008-08-08 16:26:53.000000000 -0400
@@ -3,12 +3,13 @@
watch \- execute a program periodically, showing output fullscreen
.SH SYNOPSIS
.B watch
-.I [\-dhvt] [\-n <seconds>] [\-\-differences[=cumulative]] [\-\-help]
[\-\-interval=<seconds>] [\-\-no\-title] [\-\-version] <command>
+.I [\-bdhvt] [\-n <seconds>] [\-\-beep] [\-\-differences[=cumulative]]
[\-\-help] [\-\-interval=<seconds>] [\-\-no\-title] [\-\-version] <command>
.SH DESCRIPTION
.BR watch
runs
.I command
-repeatedly, displaying its output (the first screenfull). This allows you to
+repeatedly, displaying its output and errors (the first screenfull). This
+allows you to
watch the program output change over time. By default, the program is run
every 2 seconds; use
.I -n
@@ -28,7 +29,11 @@
or
.I --no-title
option turns off the header showing the interval, command, and current
-time at the top of the display, as well as the following blank line.
+time at the top of the display, as well as the following blank line. The
+.I -b
+or
+.I --beep
+option causes the command to beep if it has a non-zero exit.
.PP
.BR watch
will run until interrupted.
@@ -84,4 +89,5 @@
.B watch
was written by Tony Rems <[EMAIL PROTECTED]> in 1991, with mods and
corrections by Francois Pinard. It was reworked and new features added by
-Mike Coleman <[EMAIL PROTECTED]> in 1999.
+Mike Coleman <[EMAIL PROTECTED]> in 1999. The beep and error handling
features were
+added by Morty Abzug <[EMAIL PROTECTED]> in 2008.
diff -Nur procps-3.2.7.orig/watch.c procps-3.2.7/watch.c
--- procps-3.2.7.orig/watch.c 2006-06-17 05:18:38.000000000 -0400
+++ procps-3.2.7/watch.c 2008-08-08 16:35:16.000000000 -0400
@@ -8,6 +8,7 @@
* Mike Coleman <[EMAIL PROTECTED]>.
*
* Changes by Albert Cahalan, 2002-2003.
+ * stderr handling and beep option added by Morty Abzug, 2008
*/
#define VERSION "0.2.0"
@@ -35,13 +36,14 @@
{"differences", optional_argument, 0, 'd'},
{"help", no_argument, 0, 'h'},
{"interval", required_argument, 0, 'n'},
+ {"beep", no_argument, 0, 'b'},
{"no-title", no_argument, 0, 't'},
{"version", no_argument, 0, 'v'},
{0, 0, 0, 0}
};
static char usage[] =
- "Usage: %s [-dhntv] [--differences[=cumulative]] [--help] [--interval=<n>]
[--no-title] [--version] <command>\n";
+ "Usage: %s [-bdhntv] [--beep] [--differences[=cumulative]] [--help]
[--interval=<n>] [--no-title] [--version] <command>\n";
static char *progname;
@@ -140,17 +142,24 @@
int optc;
int option_differences = 0,
option_differences_cumulative = 0,
+ option_beep = 0,
option_help = 0, option_version = 0;
double interval = 2;
char *command;
int command_length = 0; /* not including final \0 */
+ int pipefd[2];
+ int status;
+ pid_t child;
setlocale(LC_ALL, "");
progname = argv[0];
- while ((optc = getopt_long(argc, argv, "+d::hn:vt", longopts, (int *)
0))
+ while ((optc = getopt_long(argc, argv, "+bd::hn:vt", longopts, (int *)
0))
!= EOF) {
switch (optc) {
+ case 'b':
+ option_beep = 1;
+ break;
case 'd':
option_differences = 1;
if (optarg)
@@ -191,6 +200,7 @@
if (option_help) {
fprintf(stderr, usage, progname);
+ fputs(" -b, --beep\t\t\t\tbeep if the command has a non-zero
exit\n", stderr);
fputs(" -d, --differences[=cumulative]\thighlight changes
between updates\n", stderr);
fputs("\t\t(cumulative means highlighting is cumulative)\n",
stderr);
fputs(" -h, --help\t\t\t\tprint a summary of the options\n",
stderr);
@@ -261,11 +271,46 @@
free(header);
}
- if (!(p = popen(command, "r"))) {
- perror("popen");
+ /* allocate pipes */
+ if (pipe(pipefd)<0) {
+ perror("pipe");
+ do_exit(7);
+ }
+
+ /* flush stdout and stderr, since we're about to do fd stuff */
+ fflush(stdout);
+ fflush(stderr);
+
+ /* fork to prepare to run command */
+ child=fork();
+
+ if (child<0) { /* fork error */
+ perror("fork");
do_exit(2);
+ } else if (child==0) { /* in child */
+ close (pipefd[0]); /* child doesn't need read side of
pipe */
+ close (1); /* prepare to replace stdout with pipe */
+ if (dup2 (pipefd[1], 1)<0) { /* replace stdout with
write side of pipe */
+ perror("dup2");
+ exit(3);
+ }
+ dup2(1, 2); /* stderr should default to stdout */
+ status=system(command); /* watch manpage promises
quoting, so no execvp */
+ if (!WIFEXITED(status)) { /* child exits nonzero if
command does */
+ exit(1);
+ } else {
+ exit(WEXITSTATUS(status));
+ }
}
+ /* otherwise, we're in parent */
+ close(pipefd[1]); /* close write side of pipe */
+ if ((p=fdopen(pipefd[0], "r"))==NULL) {
+ perror("fdopen");
+ do_exit(5);
+ }
+
+
for (y = show_title; y < height; y++) {
int eolseen = 0, tabpending = 0;
for (x = 0; x < width; x++) {
@@ -313,7 +358,18 @@
oldeolseen = eolseen;
}
- pclose(p);
+ fclose(p);
+
+ /* harvest child process and get status, propagated from
command */
+ if (waitpid(child, &status, 0)<0) {
+ perror("waitpid");
+ do_exit(8);
+ };
+
+ /* if child process exited in error, beep if option_beep is set
*/
+ if (option_beep && (!WIFEXITED(status) || WEXITSTATUS(status)))
{
+ beep();
+ }
first_screen = 0;
refresh();
