]> git.scottworley.com Git - tl-append/blame_incremental - tl-append.c
test: Try writing to flock-locked files
[tl-append] / tl-append.c
... / ...
CommitLineData
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
13const int BUF_SIZE = 1024;
14
15const char PROMPT[] = "\33[H" /* Move cursor 'home' */
16 "\33[J" /* Clear screen */
17 "> ";
18const char ACKNOWLEDGE[] = "[OK]";
19const char WAITING[] = "[Waiting on lock...]\n";
20const struct timespec ACKNOWLEDGE_DELAY = {0, 300000000};
21
22typedef struct {
23 int interactive;
24 int fcntl_lock;
25} conf_t;
26
27conf_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
42static 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
57static 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
68static 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
90static 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
99static 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
112int 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}