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watch: exit when command output changes.

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Add new flags to watch (-g/--chgexit) so that it exits when the
output changes.  This is useful in builds and shell scripts, for
example when deploying webapps to block the remainder of the
deployment steps until after the webapp starts.

e.g. watch --chgexit curl http://foo/bar
This commit is contained in:
Kent R. Spillner 2012-01-26 08:42:37 -06:00
parent 8955ec26fe
commit 81f64657ba
2 changed files with 27 additions and 4 deletions
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6
watch.1
View File

@ -11,6 +11,7 @@ runs
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.
By default,
.B watch
will run until interrupted.
.SH OPTIONS
@ -44,6 +45,11 @@ Beep if command has a non-zero exit.
\fB\-e\fR, \fB\-\-errexit\fR
Freeze updates on command error, and exit after a key press.
.TP
\fB\-g\fR, \fB\-\-chgexit\fR
Exit when the output of
.I command
changes.
.TP
\fB\-c\fR, \fB\-\-color\fR
Interpret ANSI color sequences.
.TP

25
watch.c
View File

@ -69,6 +69,7 @@ static void __attribute__ ((__noreturn__))
" -c, --color interpret ANSI color sequences\n"
" -d, --differences highlight changes between updates\n"
" -e, --errexit exit if command has a non-zero exit\n"
" -g, --chgexit exit when output from command changes\n"
" -n, --interval <secs> seconds to wait between updates\n"
" -p, --precise attempt run command in precise intervals\n"
" -t, --no-title turn off header\n"
@ -277,7 +278,7 @@ int main(int argc, char *argv[])
option_exec = 0,
option_beep = 0,
option_color = 0,
option_errexit = 0, option_help = 0, option_version = 0;
option_errexit = 0, option_chgexit = 0, option_help = 0, option_version = 0;
double interval = 2;
char *command;
char **command_argv;
@ -292,6 +293,7 @@ int main(int argc, char *argv[])
int pipefd[2];
int status;
int exit_early = 0;
pid_t child;
static struct option longopts[] = {
@ -301,6 +303,7 @@ int main(int argc, char *argv[])
{"interval", required_argument, 0, 'n'},
{"beep", no_argument, 0, 'b'},
{"errexit", no_argument, 0, 'e'},
{"chgexit", no_argument, 0, 'g'},
{"exec", no_argument, 0, 'x'},
{"precise", no_argument, 0, 'p'},
{"no-title", no_argument, 0, 't'},
@ -314,7 +317,7 @@ int main(int argc, char *argv[])
textdomain(PACKAGE);
while ((optc =
getopt_long(argc, argv, "+bced::hn:pvtx", longopts, (int *)0))
getopt_long(argc, argv, "+bced::ghn:pvtx", longopts, (int *)0))
!= EOF) {
switch (optc) {
case 'b':
@ -331,6 +334,9 @@ int main(int argc, char *argv[])
case 'e':
option_errexit = 1;
break;
case 'g':
option_chgexit = 1;
break;
case 't':
show_title = 0;
break;
@ -425,7 +431,7 @@ int main(int argc, char *argv[])
if (precise_timekeeping)
next_loop = get_time_usec();
for (;;) {
do {
time_t t = time(NULL);
char *ts = ctime(&t);
int tsl = strlen(ts);
@ -636,6 +642,17 @@ int main(int argc, char *argv[])
tabpending = 0;
}
move(y, x);
if (!exit_early && option_chgexit) {
#ifdef WITH_WATCH8BIT
cchar_t oldc;
in_wch(&oldc);
exit_early = (wchar_t) c != oldc.chars[0];
#else
chtype oldch = inch();
unsigned char oldc = oldch & A_CHARTEXT;
exit_early = (unsigned char) c != oldc;
#endif /* WITH_WATCH8BIT */
}
if (option_differences) {
#ifdef WITH_WATCH8BIT
cchar_t oldc;
@ -705,7 +722,7 @@ int main(int argc, char *argv[])
usleep(next_loop - cur_time);
} else
usleep(interval * 1000000);
}
} while (!exit_early);
endwin();