1 /*
2 * DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
3 * Version 2, December 2004
4 *
5 * Copyright (C) 2016 Olaf Wintermann <olaf.wintermann@gmail.com>
6 *
7 * Everyone is permitted to copy and distribute verbatim or modified
8 * copies of this license document, and changing it is allowed as long
9 * as the name is changed.
10 *
11 * DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
12 * TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
13 *
14 * 0. You just DO WHAT THE FUCK YOU WANT TO.
15 */
16
17 /*
18 * This program adds a log prefix to each stdout line
19 */
20
21 #define _POSIX_SOURCE
22 #include <stdio.h>
23 #include <stdlib.h>
24 #include <unistd.h>
25 #include <pthread.h>
26 #include <time.h>
27
28 static int std_out_fd;
29 static int pipe_fds[2];
30
31 void* pipe_filter_thread(void *data) {
32 FILE *std_out = fdopen(std_out_fd, "w");
33 if(!std_out) {
34 return NULL;
35 }
36 FILE *pipe = fdopen(pipe_fds[0], "r");
37 if(!pipe) {
38 fclose(std_out);
39 return NULL;
40 }
41
42 int newline = 1;
43 int c;
44 while((c = fgetc(pipe)) != EOF) {
45 if(newline) {
46 char datebuf[64];
47 struct tm* tm;
48 time_t t;
49 time(&t);
50 tm = localtime(&t);
51 size_t len = strftime(datebuf, 64, "%Y-%m-%d %H:%M:%S stdout: ", tm);
52 fwrite(datebuf, 1, len, std_out);
53 newline = 0;
54 }
55 fputc(c, std_out);
56 if(c == '\n') {
57 newline = 1;
58 fflush(std_out);
59 }
60 }
61
62 fclose(std_out);
63 fclose(pipe);
64
65 return NULL;
66 }
67
68 int main(int argc, char** argv) {
69 std_out_fd = dup(STDOUT_FILENO);
70 if(pipe(pipe_fds) != 0) {
71 perror("pipe");
72 return EXIT_FAILURE;
73 }
74
75 // make fd 1(stdout) refer to the new pipe
76 dup2(pipe_fds[1], STDOUT_FILENO);
77 close(pipe_fds[1]);
78
79 pthread_t tid;
80 if(pthread_create(&tid, NULL, pipe_filter_thread, NULL) != 0) {
81 perror("pthread_create");
82 return EXIT_FAILURE;
83 }
84
85 printf("Hello World!\n");
86 printf("some text\nanother line\n");
87 fclose(stdout);
88
89 pthread_join(tid, NULL);
90
91 return (EXIT_SUCCESS);
92 }
93