git.scottworley.com Git - tl-append/blob - tl-append.c

   1 #define _POSIX_C_SOURCE 199309L
   2
   3 #include <errno.h>
   4 #include <fcntl.h>
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <string.h>
   8 #include <time.h>
   9 #include <unistd.h>
  10
  11 #include "common.h"
  12
  13 const int BUF_SIZE = 1024;
  14
  15 const char PROMPT[] = "\33[H" /* Move cursor 'home' */
  16                       "\33[J" /* Clear screen */
  17                       "> ";
  18 const char ACKNOWLEDGE[] = "[OK]";
  19 const char WAITING[] = "[Waiting on lock...]\n";
  20 const struct timespec ACKNOWLEDGE_DELAY = {0, 300000000};
  21
  22 typedef struct {
  23   int interactive;
  24 } conf_t;
  25
  26 conf_t parse_command_line(int argc, char *argv[]) {
  27   conf_t conf = {0};
  28
  29   if (argc == 2 && strcmp(argv[1], "-i") == 0 && isatty(2))
  30     conf.interactive = 1;
  31
  32   return conf;
  33 }
  34
  35 static void read_line(conf_t conf, char *buf) {
  36   if (conf.interactive)
  37     if (fputs(PROMPT, stderr) == EOF)
  38       die("I/O error writing prompt");
  39   if (fgets(buf, BUF_SIZE, stdin) == NULL) {
  40     if (ferror(stdin))
  41       die("I/O error reading line");
  42     if (feof(stdin)) {
  43       buf[0] = '\0'; /* Unclear if fgets does this already */
  44       return;
  45     }
  46     die("Unexpected error reading line");
  47   }
  48 }
  49
  50 static void write_line(const char *now, FILE *f, const char *line) {
  51   if (f == NULL)
  52     die_err("Error opening output file");
  53   if (fputs(now, f) == EOF)
  54     die("Error writing to output file");
  55   if (fputc(' ', f) == EOF)
  56     die("Error writing to output file");
  57   if (fputs(line, f) == EOF)
  58     die("Error writing to output file");
  59 }
  60
  61 static void take_lock(FILE *f) {
  62   struct flock lock;
  63   lock.l_type = F_WRLCK;
  64   lock.l_whence = SEEK_SET;
  65   lock.l_start = 0;
  66   lock.l_len = 0;
  67   int fd = fileno(f);
  68   if (fd == -1)
  69     die_err("Couldn't get file descriptor for locking");
  70   if (fcntl(fd, F_SETLK, &lock) == 0)
  71     return;
  72   if (errno != EACCES && errno != EAGAIN)
  73     die_err("Couldn't take lock");
  74   if (fputs(WAITING, stderr) == EOF)
  75     die("Error writing waiting message");
  76   if (fcntl(fd, F_SETLKW, &lock) == 0)
  77     return;
  78   die_err("Couldn't take lock");
  79 }
  80
  81 static void write_acknowledgment(conf_t conf) {
  82   if (conf.interactive) {
  83     if (fputs(ACKNOWLEDGE, stderr) == EOF)
  84       die("Error writing acknowledgment");
  85     if (nanosleep(&ACKNOWLEDGE_DELAY, NULL) == -1 && errno != EINTR)
  86       die_err("Error sleeping");
  87   }
  88 }
  89
  90 static void lock_and_write_line(conf_t conf, const char *line) {
  91   const char *now = encode_time(time(NULL));
  92   FILE *f = fopen(FILENAME, "a");
  93
  94   take_lock(f);
  95   write_line(now, f, line);
  96
  97   if (fclose(f) != 0)
  98     die_err("Error closing output file");
  99
 100   write_acknowledgment(conf);
 101 }
 102
 103 int main(int argc, char *argv[]) {
 104   conf_t conf = parse_command_line(argc, argv);
 105   char buf[BUF_SIZE];
 106   for (read_line(conf, buf); buf[0]; read_line(conf, buf)) {
 107     lock_and_write_line(conf, buf);
 108   }
 109   return 0;
 110 }