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 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * General Public License for more details.
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
31 #include <sys/types.h>
39 static const long KEY_ID = 0x414e4547; /*"GENA"*/
41 static struct shbuf_ds {
42 int size; // size of data written
43 int head; // start of message list
44 int tail; // end of message list
45 char data[1]; // data/messages
46 } *buf = NULL; // shared memory pointer
49 // Semaphore operation structures
50 static struct sembuf SMrup[1] = {{0, -1, IPC_NOWAIT | SEM_UNDO}}; // set SMrup
51 static struct sembuf SMrdn[2] = {{1, 0}, {0, +1, SEM_UNDO}}; // set SMrdn
53 static int log_shmid = -1; // ipc shared memory id
54 static int log_semid = -1; // ipc semaphore id
55 static jmp_buf jmp_env;
57 static void error_exit(const char *str);
58 static void interrupted(int sig);
61 * sem_up - up()'s a semaphore.
63 static inline void sem_up(int semid)
65 if ( semop(semid, SMrup, 1) == -1 )
66 error_exit("semop[SMrup]");
70 * sem_down - down()'s a semaphore
72 static inline void sem_down(int semid)
74 if ( semop(semid, SMrdn, 2) == -1 )
75 error_exit("semop[SMrdn]");
78 extern int logread_main(int argc, char **argv)
83 if (argc == 2 && strcmp(argv[1],"-f")==0) {
86 /* no options, no getopt */
91 // handle intrrupt signal
92 if (setjmp(jmp_env)) goto output_end;
94 // attempt to redefine ^C signal
95 signal(SIGINT, interrupted);
97 if ( (log_shmid = shmget(KEY_ID, 0, 0)) == -1)
98 error_exit("Can't find circular buffer");
100 // Attach shared memory to our char*
101 if ( (buf = shmat(log_shmid, NULL, SHM_RDONLY)) == NULL)
102 error_exit("Can't get access to circular buffer from syslogd");
104 if ( (log_semid = semget(KEY_ID, 0, 0)) == -1)
105 error_exit("Can't get access to semaphone(s) for circular buffer from syslogd");
107 // Suppose atomic memory move
108 i = follow ? buf->tail : buf->head;
119 //printf("head: %i tail: %i size: %i\n",buf->head,buf->tail,buf->size);
120 if (buf->head == buf->tail || i==buf->tail) {
123 sleep(1); /* TODO: replace me with a sleep_on */
126 printf("<empty syslog>\n");
132 log_len = buf->tail - i;
134 log_len += buf->size;
135 buf_data = (char *)malloc(log_len);
137 error_exit("malloc failed");
140 memcpy(buf_data, buf->data+i, buf->size-i);
141 memcpy(buf_data+buf->size-i, buf->data, buf->tail);
143 memcpy(buf_data, buf->data+i, buf->tail-i);
148 while ( i != buf->tail) {
149 printf("%s", buf->data+i);
150 i+= strlen(buf->data+i) + 1;
155 // release the lock on the log chain
159 for (j=0; j < log_len; j+=strlen(buf_data+j)+1) {
160 printf("%s", buf_data+j);
175 static void interrupted(int sig){
176 signal(SIGINT, SIG_IGN);
180 static void error_exit(const char *str){
182 //release all acquired resources