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 <sys/file.h>
   9 #include <time.h>
  10 #include <unistd.h>
  11
  12 #include "common.h"
  13
  14 const int BUF_SIZE = 1024;
  15
  16 const char PROMPT[] = "\33[H" /* Move cursor 'home' */
  17                       "\33[J" /* Clear screen */
  18                       "> ";
  19 const char ACKNOWLEDGE[] = "[OK]";
  20 const char WAITING[] = "[Waiting on lock...]\n";
  21 const struct timespec ACKNOWLEDGE_DELAY = {0, 300000000};
  22
  23 typedef struct {
  24   int interactive;
  25   int fcntl_lock;
  26   int flock_lock;
  27 } conf_t;
  28
  29 conf_t parse_command_line(int argc, char *argv[]) {
  30   conf_t conf;
  31   conf.interactive = 0;
  32   conf.fcntl_lock = 1;
  33   conf.flock_lock = 1;
  34
  35   for (int i = 1; i < argc; i++) {
  36     if (strcmp(argv[i], "-i") == 0 && isatty(2))
  37       conf.interactive = 1;
  38     if (strcmp(argv[i], "--no-fnctl-lock") == 0)
  39       conf.fcntl_lock = 0;
  40     if (strcmp(argv[i], "--no-flock-lock") == 0)
  41       conf.flock_lock = 0;
  42   }
  43
  44   return conf;
  45 }
  46
  47 static void read_line(conf_t *conf, char *buf) {
  48   if (conf->interactive)
  49     if (fputs(PROMPT, stderr) == EOF)
  50       die("I/O error writing prompt");
  51   if (fgets(buf, BUF_SIZE, stdin) == NULL) {
  52     if (ferror(stdin))
  53       die("I/O error reading line");
  54     if (feof(stdin)) {
  55       buf[0] = '\0'; /* Unclear if fgets does this already */
  56       return;
  57     }
  58     die("Unexpected error reading line");
  59   }
  60 }
  61
  62 static void write_line(const char *now, FILE *f, const char *line) {
  63   if (f == NULL)
  64     die_err("Error opening output file");
  65   if (fputs(now, f) == EOF)
  66     die("Error writing to output file");
  67   if (fputc(' ', f) == EOF)
  68     die("Error writing to output file");
  69   if (fputs(line, f) == EOF)
  70     die("Error writing to output file");
  71 }
  72
  73 static void take_fcntl_lock(conf_t *conf, FILE *f) {
  74   if (!conf->fcntl_lock)
  75     return;
  76   struct flock lock;
  77   lock.l_type = F_WRLCK;
  78   lock.l_whence = SEEK_SET;
  79   lock.l_start = 0;
  80   lock.l_len = 0;
  81   int fd = fileno(f);
  82   if (fd == -1)
  83     die_err("Couldn't get file descriptor for locking");
  84   if (fcntl(fd, F_SETLK, &lock) == 0)
  85     return;
  86   if (errno != EACCES && errno != EAGAIN)
  87     die_err("Couldn't take fcntl lock");
  88   if (fputs(WAITING, stderr) == EOF)
  89     die("Error writing waiting message");
  90   if (fcntl(fd, F_SETLKW, &lock) == 0)
  91     return;
  92   die_err("Couldn't take fcntl lock");
  93 }
  94
  95 static void take_flock_lock(conf_t *conf, FILE *f) {
  96   if (!conf->flock_lock)
  97     return;
  98   int fd = fileno(f);
  99   if (fd == -1)
 100     die_err("Couldn't get file descriptor for locking");
 101   if (flock(fd, LOCK_EX | LOCK_NB) == 0)
 102     return;
 103   if (errno != EWOULDBLOCK)
 104     die_err("Couldn't take flock lock");
 105   if (fputs(WAITING, stderr) == EOF)
 106     die("Error writing waiting message");
 107   if (flock(fd, LOCK_EX) == 0)
 108     return;
 109   die_err("Couldn't take flock lock");
 110 }
 111
 112 static void take_lock(conf_t *conf, FILE *f) {
 113   take_fcntl_lock(conf, f);
 114   take_flock_lock(conf, f);
 115 }
 116
 117 static void write_acknowledgment(conf_t *conf) {
 118   if (conf->interactive) {
 119     if (fputs(ACKNOWLEDGE, stderr) == EOF)
 120       die("Error writing acknowledgment");
 121     if (nanosleep(&ACKNOWLEDGE_DELAY, NULL) == -1 && errno != EINTR)
 122       die_err("Error sleeping");
 123   }
 124 }
 125
 126 static void lock_and_write_line(conf_t *conf, const char *line) {
 127   const char *now = encode_time(time(NULL));
 128   FILE *f = fopen(FILENAME, "a");
 129
 130   take_lock(conf, f);
 131   write_line(now, f, line);
 132
 133   if (fclose(f) != 0)
 134     die_err("Error closing output file");
 135
 136   write_acknowledgment(conf);
 137 }
 138
 139 int main(int argc, char *argv[]) {
 140   conf_t conf = parse_command_line(argc, argv);
 141   char buf[BUF_SIZE];
 142   for (read_line(&conf, buf); buf[0]; read_line(&conf, buf)) {
 143     lock_and_write_line(&conf, buf);
 144   }
 145   return 0;
 146 }