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/* vi: set sw=4 ts=4: */
/*
* circular buffer syslog implementation for busybox
*
* Copyright (C) 2000 by Gennady Feldman <gfeldman@cachier.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
* 02111-1307 USA
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/types.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <signal.h>
#include <setjmp.h>
#include "busybox.h"
static const long KEY_ID = 0x414e4547; /*"GENA"*/
static struct shbuf_ds {
int size; // size of data written
int head; // start of message list
int tail; // end of message list
char data[1]; // data/messages
} *buf = NULL; // shared memory pointer
// Semaphore operation structures
static struct sembuf SMrup[1] = {{0, -1, IPC_NOWAIT | SEM_UNDO}}; // set SMrup
static struct sembuf SMrdn[2] = {{1, 0}, {0, +1, SEM_UNDO}}; // set SMrdn
static int shmid = -1; // ipc shared memory id
static int semid = -1; // ipc semaphore id
static jmp_buf jmp_env;
static void error_exit(const char *str);
static void interrupted(int sig);
/*
* sem_up - up()'s a semaphore.
*/
static inline void sem_up(int semid)
{
if ( semop(semid, SMrup, 1) == -1 )
error_exit("semop[SMrup]");
}
/*
* sem_down - down()'s a semaphore
*/
static inline void sem_down(int semid)
{
if ( semop(semid, SMrdn, 2) == -1 )
error_exit("semop[SMrdn]");
}
extern int logread_main(int argc, char **argv)
{
int i;
/* no options, no getopt */
if (argc > 1)
show_usage();
// handle intrrupt signal
if (setjmp(jmp_env)) goto output_end;
// attempt to redefine ^C signal
signal(SIGINT, interrupted);
if ( (shmid = shmget(KEY_ID, 0, 0)) == -1)
error_exit("Can't find circular buffer");
// Attach shared memory to our char*
if ( (buf = shmat(shmid, NULL, SHM_RDONLY)) == NULL)
error_exit("Can't get access to circular buffer from syslogd");
if ( (semid = semget(KEY_ID, 0, 0)) == -1)
error_exit("Can't get access to semaphone(s) for circular buffer from syslogd");
sem_down(semid);
// Read Memory
i=buf->head;
//printf("head: %i tail: %i size: %i\n",buf->head,buf->tail,buf->size);
if (buf->head == buf->tail) {
printf("<empty syslog>\n");
}
while ( i != buf->tail) {
printf("%s", buf->data+i);
i+= strlen(buf->data+i) + 1;
if (i >= buf->size )
i=0;
}
sem_up(semid);
output_end:
if (shmid != -1)
shmdt(buf);
return EXIT_SUCCESS;
}
static void interrupted(int sig){
signal(SIGINT, SIG_IGN);
longjmp(jmp_env, 1);
}
static void error_exit(const char *str){
perror(str);
//release all acquired resources
if (shmid != -1)
shmdt(buf);
exit(1);
}
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