f7dd10f67

Glenn L McGrath

2003-09-26

FAILED Duration: 91s

Subject

Patch from Fillod Stephane 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.

Binary

No binary (build failed)

Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

—

Build Log

(log yok)

Commit Diff GitHub →

sysklogd/logread.c +68 -18

sysklogd/logread.c+68 -18

@@ -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;
-
-	//printf("head: %i tail: %i size: %i\n",buf->head,buf->tail,buf->size);
-	if (buf->head == buf->tail) {
-	printf("<empty syslog>\n");
-	}
+	// Suppose atomic memory move
+	i = follow ? buf->tail : buf->head;
+
+	do {
+	#undef RC_LOGREAD
+	#ifdef RC_LOGREAD
+	char *buf_data;
+	int log_len,j;
+	#endif
+
+	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");
+	}
+	}

-	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);
+	// 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)