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   int fcntl_lock;
  25 } conf_t;
  26
  27 conf_t parse_command_line(int argc, char *argv[]) {
  28   conf_t conf;
  29   conf.interactive = 0;
  30   conf.fcntl_lock = 1;
  31
  32   for (int i = 1; i < argc; i++) {
  33     if (strcmp(argv[i], "-i") == 0 && isatty(2))
  34       conf.interactive = 1;
  35     if (strcmp(argv[i], "--no-fnctl-lock") == 0)
  36       conf.fcntl_lock = 0;
  37   }
  38
  39   return conf;
  40 }
  41
  42 static void read_line(conf_t *conf, char *buf) {
  43   if (conf->interactive)
  44     if (fputs(PROMPT, stderr) == EOF)
  45       die("I/O error writing prompt");
  46   if (fgets(buf, BUF_SIZE, stdin) == NULL) {
  47     if (ferror(stdin))
  48       die("I/O error reading line");
  49     if (feof(stdin)) {
  50       buf[0] = '\0'; /* Unclear if fgets does this already */
  51       return;
  52     }
  53     die("Unexpected error reading line");
  54   }
  55 }
  56
  57 static void write_line(const char *now, FILE *f, const char *line) {
  58   if (f == NULL)
  59     die_err("Error opening output file");
  60   if (fputs(now, f) == EOF)
  61     die("Error writing to output file");
  62   if (fputc(' ', f) == EOF)
  63     die("Error writing to output file");
  64   if (fputs(line, f) == EOF)
  65     die("Error writing to output file");
  66 }
  67
  68 static void take_lock(conf_t *conf, FILE *f) {
  69   if (!conf->fcntl_lock)
  70     return;
  71   struct flock lock;
  72   lock.l_type = F_WRLCK;
  73   lock.l_whence = SEEK_SET;
  74   lock.l_start = 0;
  75   lock.l_len = 0;
  76   int fd = fileno(f);
  77   if (fd == -1)
  78     die_err("Couldn't get file descriptor for locking");
  79   if (fcntl(fd, F_SETLK, &lock) == 0)
  80     return;
  81   if (errno != EACCES && errno != EAGAIN)
  82     die_err("Couldn't take lock");
  83   if (fputs(WAITING, stderr) == EOF)
  84     die("Error writing waiting message");
  85   if (fcntl(fd, F_SETLKW, &lock) == 0)
  86     return;
  87   die_err("Couldn't take lock");
  88 }
  89
  90 static void write_acknowledgment(conf_t *conf) {
  91   if (conf->interactive) {
  92     if (fputs(ACKNOWLEDGE, stderr) == EOF)
  93       die("Error writing acknowledgment");
  94     if (nanosleep(&ACKNOWLEDGE_DELAY, NULL) == -1 && errno != EINTR)
  95       die_err("Error sleeping");
  96   }
  97 }
  98
  99 static void lock_and_write_line(conf_t *conf, const char *line) {
 100   const char *now = encode_time(time(NULL));
 101   FILE *f = fopen(FILENAME, "a");
 102
 103   take_lock(conf, f);
 104   write_line(now, f, line);
 105
 106   if (fclose(f) != 0)
 107     die_err("Error closing output file");
 108
 109   write_acknowledgment(conf);
 110 }
 111
 112 int main(int argc, char *argv[]) {
 113   conf_t conf = parse_command_line(argc, argv);
 114   char buf[BUF_SIZE];
 115   for (read_line(&conf, buf); buf[0]; read_line(&conf, buf)) {
 116     lock_and_write_line(&conf, buf);
 117   }
 118   return 0;
 119 }