Write to pipe form the sensor directly

shell redirection isn't sufficient because the writer process is killed
upon closing of the pipe by the reader.

diff --git a/x5/khatus_sensor_time.c b/x5/khatus_sensor_time.c
index f156f45..983ebdf 100644 (file)
--- a/x5/khatus_sensor_time.c
+++ b/x5/khatus_sensor_time.c
@@ -1,5 +1,8 @@
+#include <assert.h>
+#include <ctype.h>
 #include <errno.h>
-#include <stdarg.h>
+#include <fcntl.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -9,19 +12,24 @@
 #include "khatus_lib_log.h"
 #include "khatus_lib_time.h"
 
+#define usage(...) {print_usage(); fprintf(stderr, "Error:\n    " __VA_ARGS__); exit(EXIT_FAILURE);}
+
+#define MAX_LEN 20
+#define END_OF_MESSAGE '\n'
+
 char *argv0;
 
 void
-usage()
+print_usage()
 {
        printf(
-           "%s: [OPT ...]\n"
+           "%s: [OPT ...] FIFO\n"
            "\n"
+           "FIFO = string    # path to fifo file\n"
            "OPT = -i int     # interval\n"
            "    | -f string  # format string\n"
            "    | -h         # help message (i.e. what you're reading now :) )\n",
            argv0);
-       fatal("usage\n");
 }
 
 int
@@ -34,10 +42,19 @@ main(int argc, char **argv)
 
        time_t t;
        struct timespec ti;
-       char buf[128];
+       char buf[MAX_LEN];
        char c;
 
-       memset(buf, '\0', 128);
+       char *fifo_name;
+       int   fifo_fd = -1;
+
+       int n = 0;  /* written */
+       int r = 0;  /* remaining */
+       int i = 0;  /* buffer position */
+
+       signal(SIGPIPE, SIG_IGN);  /* Handling manually */
+
+       memset(buf, '\0', MAX_LEN);
        while ((c = getopt(argc, argv, "f:i:h")) != -1)
                switch (c) {
                case 'f':
@@ -48,17 +65,56 @@ main(int argc, char **argv)
                        opt_interval = atof(optarg);
                        break;
                case 'h':
-                       usage();
-                       break;
+                       print_usage();
+                       return 0;
+               case '?':
+                       if (optopt == 'f' || optopt == 'i')
+                               fprintf(stderr,
+                                       "Option -%c requires an argument.\n",
+                                       optopt);
+                       else if (isprint(optopt))
+                               fprintf (stderr,
+                                       "Unknown option `-%c'.\n",
+                                       optopt);
+                       else
+                               fprintf(stderr,
+                                       "Unknown option character `\\x%x'.\n",
+                                       optopt);
+                       return 1;
                default:
-                       usage();
+                       assert(0);
                }
+       fifo_name = argv[optind];
+       debug("fifo_name: %s\n", fifo_name);
+       if (!fifo_name)
+               usage("No filename was provided\n");
        ti = timespec_of_float(opt_interval);
        for (;;) {
+               debug("openning \"%s\"\n", fifo_name);
+               fifo_fd = open(fifo_name, O_WRONLY);
+               if (fifo_fd < 0)
+                       fatal("Failed to open FIFO file: \"%s\". Error: %s\n",
+                           fifo_name,
+                           strerror(errno));
+               debug("openned. fd: %d\n", fifo_fd);
                t = time(NULL);
-               strftime(buf, sizeof(buf), opt_fmt, localtime(&t));
-               puts(buf);
-               fflush(stdout);
+               strftime(buf, MAX_LEN, opt_fmt, localtime(&t));
+               r = strlen(buf);
+               buf[r] = END_OF_MESSAGE;
+               for (i = 0; (n = write(fifo_fd, buf + i++, 1)) && r; r--)
+                       ;
+               if (n < 0)
+                       fatal("Failed to write to %s. Err num: %d, Err msg: %s\n",
+                           fifo_name,
+                           errno,
+                           strerror(errno));
+               if (close(fifo_fd) < 0)
+                       fatal("Failed to close %s. Err num: %d, Err msg: %s\n",
+                           fifo_name,
+                           errno,
+                           strerror(errno));
+               fifo_fd = -1;
+               debug("closed. fd: %d\n", fifo_fd);
                snooze(&ti);
        }
        return EXIT_SUCCESS;