| SENDSYSLOG(2) | System Calls Manual | SENDSYSLOG(2) |
sendsyslog — send
a message to syslogd
#include
<sys/syslog.h>
#include <sys/types.h>
int
sendsyslog(const
char *msg, size_t
len, int
flags);
The
sendsyslog()
function is used to transmit a
syslog(3) formatted message
direct to syslogd(8) without
requiring the allocation of a socket. The msg is not
NUL terminated and its len is limited to 8192 bytes.
If LOG_CONS is specified in the
flags argument, and
syslogd(8) is not accepting
messages, the message will be sent to the console. This is used internally
by syslog_r(3), so that
messages can be sent during difficult situations. If sending to
syslogd(8) fails, up to 100
messages are stashed in the kernel. After that, dropped messages are
counted. When syslogd(8) works
again, before the next message, stashed messages and possibly a warning with
the drop counter, error number, and pid is logged.
To receive messages from the kernel,
syslogd(8) has to create a
datagram socket pair and register one end. This registration is done by
opening the /dev/klog device and passing one file
descriptor of the socket pair as argument to
ioctl(2)
LIOCSFD invoked on the klog file descriptor. After
that the messages can be read from the other end of the socket pair. By
utilizing /dev/klog the access to log messages is
limited to processes that may open this device.
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
sendsyslog() can fail if:
EFAULT]EMSGSIZE]ENOBUFS]ENOTCONN]The sendsyslog() function call appeared in
OpenBSD 5.6. The flags
argument was added in OpenBSD 6.0.
| March 9, 2021 | openbsd |