watch: Add --equexit option

This commit adds a new option called `--equexit` which is the opposite
of `--chgexit`. This option makes it possible to exit when the output
of the given command does not change for the given number of cycles.
A download operation could be given as a use-case since `watch` will
exit when the output does not change anymore, in other words, when
the download is completed.

References:
 procps-ng/procps#232

Signed-off-by: Orhun Parmaksız <orhunparmaksiz@gmail.com>

diff --git a/watch.1 b/watch.1
index 5f077628d017da7a58aaf5e17ea694a632241bfe..cef2cab2e02646f1eeca81802aebdf80eaf960f4 100644 (file)
--- a/watch.1
+++ b/watch.1
@@ -53,6 +53,11 @@ Exit when the output of
 .I command
 changes.
 .TP
+\fB\-q\fR, \fB\-\-equexit\fR <cycles>
+Exit when output of
+.I command
+does not change for the given number of cycles.
+.TP
 \fB\-c\fR, \fB\-\-color\fR
 Interpret ANSI color and style sequences.
 .TP

diff --git a/watch.c b/watch.c
index 0ba6b3fc4612989fc464d2beb2e7dd8a66ce5f57..a69a402927ff25a468d78e98923e488291ada4b5 100644 (file)
--- a/watch.c
+++ b/watch.c
@@ -71,6 +71,7 @@ static int flags;
 #define WATCH_COLOR    (1 << 5)
 #define WATCH_ERREXIT  (1 << 6)
 #define WATCH_CHGEXIT  (1 << 7)
+#define WATCH_EQUEXIT  (1 << 8)
 
 static int curses_started = 0;
 static long height = 24, width = 80;
@@ -96,6 +97,8 @@ static void __attribute__ ((__noreturn__))
                 "                         highlight changes between updates\n"), out);
        fputs(_("  -e, --errexit          exit if command has a non-zero exit\n"), out);
        fputs(_("  -g, --chgexit          exit when output from command changes\n"), out);
+       fputs(_("  -q, --equexit <cycles>\n"
+                               "                         exit when output from command does not change\n"), out);
        fputs(_("  -n, --interval <secs>  seconds to wait between updates\n"), out);
        fputs(_("  -p, --precise          attempt run command in precise intervals\n"), out);
        fputs(_("  -t, --no-title         turn off header\n"), out);
@@ -561,6 +564,8 @@ static int run_command(char *restrict command, char **restrict command_argv)
        int pipefd[2];
        pid_t child;
        int exit_early = 0;
+       int buffer_size = 0;
+       int unchanged_buffer = 0;
        int status;
 
        /* allocate pipes */
@@ -703,6 +708,20 @@ static int run_command(char *restrict command, char **restrict command_argv)
                                chtype oldch = inch();
                                unsigned char oldc = oldch & A_CHARTEXT;
                                exit_early = (unsigned char)c != oldc;
+#endif
+                       }
+                       if (!first_screen && !exit_early && (flags & WATCH_EQUEXIT)) {
+                               buffer_size++;
+#ifdef WITH_WATCH8BIT
+                               cchar_t oldc;
+                               in_wch(&oldc);
+                               if ((wchar_t) c == oldc.chars[0])
+                                       unchanged_buffer++;
+#else
+                               chtype oldch = inch();
+                               unsigned char oldc = oldch & A_CHARTEXT;
+                               if ((unsigned char)c == oldc)
+                                       unchanged_buffer++;
 #endif
                        }
                        if (flags & WATCH_DIFF) {
@@ -753,7 +772,6 @@ static int run_command(char *restrict command, char **restrict command_argv)
 
        fclose(p);
 
-
        /* harvest child process and get status, propagated from command */
        if (waitpid(child, &status, 0) < 0)
                xerr(8, _("waitpid"));
@@ -771,6 +789,10 @@ static int run_command(char *restrict command, char **restrict command_argv)
                        exit(8);
                }
        }
+
+       if (unchanged_buffer == buffer_size && (flags & WATCH_EQUEXIT))
+               exit_early = 1;
+
        first_screen = 0;
        refresh();
        return exit_early;
@@ -780,6 +802,8 @@ int main(int argc, char *argv[])
 {
        int optc;
        double interval = 2;
+       int max_cycles = 1;
+       int cycle_count = 0;
        char *interval_string;
        char *command;
        char **command_argv;
@@ -799,6 +823,7 @@ int main(int argc, char *argv[])
                {"beep", no_argument, 0, 'b'},
                {"errexit", no_argument, 0, 'e'},
                {"chgexit", no_argument, 0, 'g'},
+               {"equexit", required_argument, 0, 'q'},
                {"exec", no_argument, 0, 'x'},
                {"precise", no_argument, 0, 'p'},
                {"no-title", no_argument, 0, 't'},
@@ -820,7 +845,7 @@ int main(int argc, char *argv[])
                interval = strtod_nol_or_err(interval_string, _("Could not parse interval from WATCH_INTERVAL"));
 
        while ((optc =
-               getopt_long(argc, argv, "+bced::ghn:pvtwx", longopts, (int *)0))
+               getopt_long(argc, argv, "+bced::ghq:n:pvtwx", longopts, (int *)0))
               != EOF) {
                switch (optc) {
                case 'b':
@@ -840,6 +865,10 @@ int main(int argc, char *argv[])
                case 'g':
                        flags |= WATCH_CHGEXIT;
                        break;
+               case 'q':
+                       flags |= WATCH_EQUEXIT;
+                       max_cycles = strtod_nol_or_err(optarg, _("failed to parse argument"));
+                       break;
                case 't':
                        show_title = 0;
                        break;
@@ -955,9 +984,18 @@ int main(int argc, char *argv[])
                        output_header(command, interval);
 #endif /* WITH_WATCH8BIT */
 
-               if (run_command(command, command_argv))
+               int exit = run_command(command, command_argv);
+               if (flags & WATCH_EQUEXIT) {
+                       if (cycle_count == max_cycles && exit) {
+                               break;
+                       } else if (exit) {
+                               cycle_count++;
+                       } else {
+                               cycle_count = 0;
+                       }
+               } else if (exit) {
                        break;
-
+               }
 
                if (precise_timekeeping) {
                        watch_usec_t cur_time = get_time_usec();