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logread: implement dumpfollow mode of operation

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This is basically a combination of the default (dump mode) and -f
(follow mode). Specifying -F makes logread first dump the log buffer and
then immediately start following it.

function                                             old     new   delta
packed_usage                                       30412   30443     +31
logread_main                                         491     497      +6

Signed-off-by: Phil Sutter <phil.sutter@viprinet.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Phil Sutter 2015-03-22 17:36:20 +01:00 committed by Denys Vlasenko
parent 6d8ea1d50e
commit 92edab1aa6
1 changed files with 11 additions and 5 deletions
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16
sysklogd/logread.c
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@ -10,10 +10,11 @@
*/
//usage:#define logread_trivial_usage
//usage: "[-f]"
//usage: "[-fF]"
//usage:#define logread_full_usage "\n\n"
//usage: "Show messages in syslogd's circular buffer\n"
//usage: "\n -f Output data as log grows"
//usage: "\n -F Same as -f, but dump buffer first"
#include "libbb.h"
#include <sys/ipc.h>
@ -83,7 +84,7 @@ int logread_main(int argc UNUSED_PARAM, char **argv)
unsigned cur;
int log_semid; /* ipc semaphore id */
int log_shmid; /* ipc shared memory id */
smallint follow = getopt32(argv, "f");
int follow = getopt32(argv, "fF");
INIT_G();
@ -106,7 +107,7 @@ int logread_main(int argc UNUSED_PARAM, char **argv)
/* Max possible value for tail is shbuf->size - 1 */
cur = shbuf->tail;
/* Loop for logread -f, one pass if there was no -f */
/* Loop for -f or -F, one pass otherwise */
do {
unsigned shbuf_size;
unsigned shbuf_tail;
@ -129,7 +130,12 @@ int logread_main(int argc UNUSED_PARAM, char **argv)
printf("cur:%u tail:%u size:%u\n",
cur, shbuf_tail, shbuf_size);
if (!follow) {
if (!(follow & 1)) { /* not -f */
/* if -F, "convert" it to -f, so that we dont
* dump the entire buffer on each iteration
*/
follow >>= 1;
/* advance to oldest complete message */
/* find NUL */
cur += strlen(shbuf_data + cur);
@ -142,7 +148,7 @@ int logread_main(int argc UNUSED_PARAM, char **argv)
cur++;
if (cur >= shbuf_size) /* last byte in buffer? */
cur = 0;
} else { /* logread -f */
} else { /* -f */
if (cur == shbuf_tail) {
sem_up(log_semid);
fflush_all();