]> git.scottworley.com Git - tl-append/blob - tl-append.c
6cc068a718627416e929d7adf046484d01064489
[tl-append] / 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;
28 conf.interactive = 0;
29
30 for (int i = 1; i < argc; i++) {
31 if (strcmp(argv[i], "-i") == 0 && isatty(2))
32 conf.interactive = 1;
33 }
34
35 return conf;
36 }
37
38 static void read_line(conf_t *conf, char *buf) {
39 if (conf->interactive)
40 if (fputs(PROMPT, stderr) == EOF)
41 die("I/O error writing prompt");
42 if (fgets(buf, BUF_SIZE, stdin) == NULL) {
43 if (ferror(stdin))
44 die("I/O error reading line");
45 if (feof(stdin)) {
46 buf[0] = '\0'; /* Unclear if fgets does this already */
47 return;
48 }
49 die("Unexpected error reading line");
50 }
51 }
52
53 static void write_line(const char *now, FILE *f, const char *line) {
54 if (f == NULL)
55 die_err("Error opening output file");
56 if (fputs(now, f) == EOF)
57 die("Error writing to output file");
58 if (fputc(' ', f) == EOF)
59 die("Error writing to output file");
60 if (fputs(line, f) == EOF)
61 die("Error writing to output file");
62 }
63
64 static void take_lock(FILE *f) {
65 struct flock lock;
66 lock.l_type = F_WRLCK;
67 lock.l_whence = SEEK_SET;
68 lock.l_start = 0;
69 lock.l_len = 0;
70 int fd = fileno(f);
71 if (fd == -1)
72 die_err("Couldn't get file descriptor for locking");
73 if (fcntl(fd, F_SETLK, &lock) == 0)
74 return;
75 if (errno != EACCES && errno != EAGAIN)
76 die_err("Couldn't take lock");
77 if (fputs(WAITING, stderr) == EOF)
78 die("Error writing waiting message");
79 if (fcntl(fd, F_SETLKW, &lock) == 0)
80 return;
81 die_err("Couldn't take lock");
82 }
83
84 static void write_acknowledgment(conf_t *conf) {
85 if (conf->interactive) {
86 if (fputs(ACKNOWLEDGE, stderr) == EOF)
87 die("Error writing acknowledgment");
88 if (nanosleep(&ACKNOWLEDGE_DELAY, NULL) == -1 && errno != EINTR)
89 die_err("Error sleeping");
90 }
91 }
92
93 static void lock_and_write_line(conf_t *conf, const char *line) {
94 const char *now = encode_time(time(NULL));
95 FILE *f = fopen(FILENAME, "a");
96
97 take_lock(f);
98 write_line(now, f, line);
99
100 if (fclose(f) != 0)
101 die_err("Error closing output file");
102
103 write_acknowledgment(conf);
104 }
105
106 int main(int argc, char *argv[]) {
107 conf_t conf = parse_command_line(argc, argv);
108 char buf[BUF_SIZE];
109 for (read_line(&conf, buf); buf[0]; read_line(&conf, buf)) {
110 lock_and_write_line(&conf, buf);
111 }
112 return 0;
113 }