1 /* vi: set sw=4 ts=4: */
3 * circular buffer syslog implementation for busybox
5 * Copyright (C) 2000 by Gennady Feldman <gfeldman@gena01.com>
7 * Maintainer: Gennady Feldman <gfeldman@gena01.com> as of Mar 12, 2001
9 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
19 enum { KEY_ID = 0x414e4547 }; /* "GENA" */
21 static struct shbuf_ds {
22 int32_t size; // size of data written
23 int32_t head; // start of message list
24 int32_t tail; // end of message list
25 char data[1]; // data/messages
26 } *buf; // shared memory pointer
28 // Semaphore operation structures
29 static struct sembuf SMrup[1] = {{0, -1, IPC_NOWAIT | SEM_UNDO}}; // set SMrup
30 static struct sembuf SMrdn[2] = {{1, 0}, {0, +1, SEM_UNDO}}; // set SMrdn
33 static void error_exit(const char *str) ATTRIBUTE_NORETURN;
34 static void error_exit(const char *str)
36 //release all acquired resources
38 bb_perror_msg_and_die(str);
42 * sem_up - up()'s a semaphore.
44 static void sem_up(int semid)
46 if (semop(semid, SMrup, 1) == -1)
47 error_exit("semop[SMrup]");
50 static void interrupted(int sig ATTRIBUTE_UNUSED)
52 signal(SIGINT, SIG_IGN);
57 int logread_main(int argc, char **argv)
60 int log_semid; /* ipc semaphore id */
61 int log_shmid; /* ipc shared memory id */
62 smallint follow = getopt32(argc, argv, "f");
64 log_shmid = shmget(KEY_ID, 0, 0);
66 bb_perror_msg_and_die("can't find syslogd buffer");
68 // Attach shared memory to our char*
69 buf = shmat(log_shmid, NULL, SHM_RDONLY);
71 bb_perror_msg_and_die("can't access syslogd buffer");
73 log_semid = semget(KEY_ID, 0, 0);
75 error_exit("can't get access to semaphores for syslogd buffer");
77 // attempt to redefine ^C signal
78 signal(SIGINT, interrupted);
80 // Suppose atomic memory move
81 cur = follow ? buf->tail : buf->head;
84 #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
88 if (semop(log_semid, SMrdn, 2) == -1)
89 error_exit("semop[SMrdn]");
92 printf("head:%i cur:%d tail:%i size:%i\n",
93 buf->head, cur, buf->tail, buf->size);
95 if (buf->head == buf->tail || cur == buf->tail) {
99 sleep(1); /* TODO: replace me with a sleep_on */
102 puts("<empty syslog>");
106 #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
107 log_len = buf->tail - cur;
109 log_len += buf->size;
110 buf_data = xmalloc(log_len);
112 if (buf->tail >= cur)
116 memcpy(buf_data, buf->data + cur, j);
119 memcpy(buf_data + buf->size - cur, buf->data, buf->tail);
122 while (cur != buf->tail) {
123 fputs(buf->data + cur, stdout);
124 cur += strlen(buf->data + cur) + 1;
125 if (cur >= buf->size)
129 // release the lock on the log chain
132 #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
133 for (j = 0; j < log_len; j += strlen(buf_data+j) + 1) {
134 fputs(buf_data + j, stdout);
142 fflush_stdout_and_exit(EXIT_SUCCESS);