NAME
sendsyslog
—
send a message to syslogd
SYNOPSIS
#include
<sys/syslog.h>
#include <sys/types.h>
int
sendsyslog
(const
char *msg, size_t
len, int
flags);
DESCRIPTION
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.
RETURN VALUES
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.
ERRORS
sendsyslog
() can fail if:
- [
EFAULT
] - An invalid user space address was specified for a parameter.
- [
EMSGSIZE
] - The socket requires that message be sent atomically, and the size of the message to be sent made this impossible.
- [
ENOBUFS
] - The system was unable to allocate an internal buffer. The operation may succeed when buffers become available.
- [
ENOTCONN
] - The message cannot be sent, likely because syslogd(8) is not running.
SEE ALSO
HISTORY
The sendsyslog
() function call appeared in
OpenBSD 5.6. The flags
argument was added in OpenBSD 6.0.