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Patch from Fillod Stephane

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Add follow mode to logread, ala "tail -f /var/log/messages"
Note: output to a slow serial terminal can have side effects
on syslog because of the semaphore. In such case, define 
RC_LOGREAD.
This commit is contained in:
Glenn L McGrath 2003-09-26 01:03:16 +00:00
parent a79220db6e
commit f7dd10f67c
1 changed files with 67 additions and 17 deletions
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84
sysklogd/logread.c
View File

@ -33,6 +33,7 @@
#include <sys/shm.h>
#include <signal.h>
#include <setjmp.h>
#include <unistd.h>
#include "busybox.h"
static const long KEY_ID = 0x414e4547; /*"GENA"*/
@ -77,10 +78,15 @@ static inline void sem_down(int semid)
extern int logread_main(int argc, char **argv)
{
int i;
int follow=0;
/* no options, no getopt */
if (argc > 1)
bb_show_usage();
if (argc == 2 && strcmp(argv[1],"-f")==0) {
follow = 1;
} else {
/* no options, no getopt */
if (argc > 1)
bb_show_usage();
}
// handle intrrupt signal
if (setjmp(jmp_env)) goto output_end;
@ -98,22 +104,66 @@ extern int logread_main(int argc, char **argv)
if ( (log_semid = semget(KEY_ID, 0, 0)) == -1)
error_exit("Can't get access to semaphone(s) for circular buffer from syslogd");
sem_down(log_semid);
// Read Memory
i=buf->head;
// Suppose atomic memory move
i = follow ? buf->tail : 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");
}
do {
#undef RC_LOGREAD
#ifdef RC_LOGREAD
char *buf_data;
int log_len,j;
#endif
while ( i != buf->tail) {
printf("%s", buf->data+i);
i+= strlen(buf->data+i) + 1;
if (i >= buf->size )
i=0;
}
sem_up(log_semid);
sem_down(log_semid);
//printf("head: %i tail: %i size: %i\n",buf->head,buf->tail,buf->size);
if (buf->head == buf->tail || i==buf->tail) {
if (follow) {
sem_up(log_semid);
sleep(1); /* TODO: replace me with a sleep_on */
continue;
} else {
printf("<empty syslog>\n");
}
}
// Read Memory
#ifdef RC_LOGREAD
log_len = buf->tail - i;
if (log_len < 0)
log_len += buf->size;
buf_data = (char *)malloc(log_len);
if (!buf_data)
error_exit("malloc failed");
if (buf->tail < i) {
memcpy(buf_data, buf->data+i, buf->size-i);
memcpy(buf_data+buf->size-i, buf->data, buf->tail);
} else {
memcpy(buf_data, buf->data+i, buf->tail-i);
}
i = buf->tail;
#else
while ( i != buf->tail) {
printf("%s", buf->data+i);
i+= strlen(buf->data+i) + 1;
if (i >= buf->size )
i=0;
}
#endif
// release the lock on the log chain
sem_up(log_semid);
#ifdef RC_LOGREAD
for (j=0; j < log_len; j+=strlen(buf_data+j)+1) {
printf("%s", buf_data+j);
if (follow)
fflush(stdout);
}
free(buf_data);
#endif
} while (follow);
output_end:
if (log_shmid != -1)