Standards
| Standards / Extensions |
C or C++ |
Dependencies |
|---|
XPG4.2
Single UNIX Specification, Version 3
|
both |
|
Format
#define _XOPEN_SOURCE_EXTENDED 1
#include <syslog.h>
void openlog(const char *ident, int logopt, int facility);
General description
The openlog()
function optionally opens a connection to the logging facility, and
sets process attributes that affect subsequent calls to the syslog()
function. The argument
ident is a string
that is prefixed to every message.
logopt is
a bit field indicating logging options. Current values of
logopt are:
- LOG_CONS
- Write messages
to the system console if they cannot be sent to the logging facility.
This option is safe to use in processes that have no controlling
terminal, since the syslog() function forks before opening the console.
- LOG_NDELAY
- Open the connection
to the logging facility immediately. Normally the open is delayed
until the first message is logged. This is useful for programs that
need to manage the order in which file descriptors are allocated..
- LOG_NOWAIT
- Do not wait
for child processes that have been forked to log messages onto the
console. This option should be used by processes that enable notification
of child termination using SIGCHLD, since the syslog()
function may otherwise block waiting for a child whose exit status
has already been collected.
- LOG_ODELAY
- Delay open
until syslog() is called.
- LOG_PID
- Log the processID
with each message. This is useful for identifying specific processes.
In the message header, the processID is surrounded by square brackets.
The code point values for the square brackets are taken from code
page IBM-1047. The value for the left square bracket is 0xAD. The
value for the right square bracket is 0xBD.
The
facility argument
encodes a default facility to be assigned to all messages that do
not have an explicit facility already encoded. The initial default
facility is as follows:
- LOG_USER
- Message generated
by random processes. This is the default facility identifier if none
is specified.
Returned value
openlog() returns no values.
No
errors are defined.