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 void usage() {
  30   die("usage: tl-append [-i] [-C dir] [--no-fnctl-lock] [--no-flock-lock]");
  31 }
  32
  33 conf_t parse_command_line(int argc, char *argv[]) {
  34   conf_t conf;
  35   conf.interactive = 0;
  36   conf.fcntl_lock = 1;
  37   conf.flock_lock = 1;
  38
  39   for (int i = 1; i < argc; i++) {
  40     if (strcmp(argv[i], "-i") == 0 && isatty(2))
  41       conf.interactive = 1;
  42     else if (strcmp(argv[i], "--no-fnctl-lock") == 0)
  43       conf.fcntl_lock = 0;
  44     else if (strcmp(argv[i], "--no-flock-lock") == 0)
  45       conf.flock_lock = 0;
  46     else if (strcmp(argv[i], "-C") == 0) {
  47       if (i + 1 >= argc)
  48         die("-C requires a directory");
  49       if (chdir(argv[i + 1]) == -1)
  50         die_err("Couldn't change directory");
  51       i++;
  52     } else
  53       usage();
  54   }
  55
  56   return conf;
  57 }
  58
  59 static void read_line(conf_t *conf, char *buf) {
  60   if (conf->interactive)
  61     if (fputs(PROMPT, stderr) == EOF)
  62       die("I/O error writing prompt");
  63   if (fgets(buf, BUF_SIZE, stdin) == NULL) {
  64     if (ferror(stdin))
  65       die("I/O error reading line");
  66     if (feof(stdin)) {
  67       buf[0] = '\0'; /* Unclear if fgets does this already */
  68       return;
  69     }
  70     die("Unexpected error reading line");
  71   }
  72 }
  73
  74 static void write_line(const char *now, FILE *f, const char *line) {
  75   if (f == NULL)
  76     die_err("Error opening output file");
  77   if (fputs(now, f) == EOF)
  78     die("Error writing to output file");
  79   if (fputc(' ', f) == EOF)
  80     die("Error writing to output file");
  81   if (fputs(line, f) == EOF)
  82     die("Error writing to output file");
  83 }
  84
  85 static void take_fcntl_lock(conf_t *conf, FILE *f) {
  86   if (!conf->fcntl_lock)
  87     return;
  88   struct flock lock;
  89   lock.l_type = F_WRLCK;
  90   lock.l_whence = SEEK_SET;
  91   lock.l_start = 0;
  92   lock.l_len = 0;
  93   int fd = fileno(f);
  94   if (fd == -1)
  95     die_err("Couldn't get file descriptor for locking");
  96   if (fcntl(fd, F_SETLK, &lock) == 0)
  97     return;
  98   if (errno != EACCES && errno != EAGAIN)
  99     die_err("Couldn't take fcntl lock");
 100   if (fputs(WAITING, stderr) == EOF)
 101     die("Error writing waiting message");
 102   if (fcntl(fd, F_SETLKW, &lock) == 0)
 103     return;
 104   die_err("Couldn't take fcntl lock");
 105 }
 106
 107 static void take_flock_lock(conf_t *conf, FILE *f) {
 108   if (!conf->flock_lock)
 109     return;
 110   int fd = fileno(f);
 111   if (fd == -1)
 112     die_err("Couldn't get file descriptor for locking");
 113   if (flock(fd, LOCK_EX | LOCK_NB) == 0)
 114     return;
 115   if (errno != EWOULDBLOCK)
 116     die_err("Couldn't take flock lock");
 117   if (fputs(WAITING, stderr) == EOF)
 118     die("Error writing waiting message");
 119   if (flock(fd, LOCK_EX) == 0)
 120     return;
 121   die_err("Couldn't take flock lock");
 122 }
 123
 124 static void take_lock(conf_t *conf, FILE *f) {
 125   take_fcntl_lock(conf, f);
 126   take_flock_lock(conf, f);
 127 }
 128
 129 static void write_acknowledgment(conf_t *conf) {
 130   if (conf->interactive) {
 131     if (fputs(ACKNOWLEDGE, stderr) == EOF)
 132       die("Error writing acknowledgment");
 133     if (nanosleep(&ACKNOWLEDGE_DELAY, NULL) == -1 && errno != EINTR)
 134       die_err("Error sleeping");
 135   }
 136 }
 137
 138 static void lock_and_write_line(conf_t *conf, const char *line) {
 139   char *now = encode_time(time(NULL));
 140   FILE *f = fopen(FILENAME, "a");
 141
 142   take_lock(conf, f);
 143   write_line(now, f, line);
 144
 145   if (fclose(f) != 0)
 146     die_err("Error closing output file");
 147
 148   free(now);
 149   write_acknowledgment(conf);
 150 }
 151
 152 int main(int argc, char *argv[]) {
 153   conf_t conf = parse_command_line(argc, argv);
 154   char buf[BUF_SIZE];
 155   for (read_line(&conf, buf); buf[0]; read_line(&conf, buf)) {
 156     lock_and_write_line(&conf, buf);
 157   }
 158   return 0;
 159 }