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int facility)
openlog opens or reopens a connection to Syslog in preparation
for submitting messages.
ident is an arbitrary identification string which future
syslog invocations will prefix to each message. This is intended
to identify the source of the message, and people conventionally set it
to the name of the program that will submit the messages.
openlog may or may not open the /dev/log socket, depending
on option. If it does, it tries to open it and connect it as a
stream socket. If that doesn't work, it tries to open it and connect it
as a datagram socket. The socket has the "Close on Exec" attribute,
so the kernel will close it if the process performs an exec.
You don't have to use openlog. If you call syslog without
having called openlog, syslog just opens the connection
implicitly and uses defaults for the information in ident and
options.
options is a bit string, with the bits as defined by the following
single bit masks:
LOG_PERROR
- If on,
openlog sets up the connection so that any syslog
on this connection writes its message to the calling process' Standard
Error stream in addition to submitting it to Syslog. If off, syslog
does not write the message to Standard Error.
LOG_CONS
- If on,
openlog sets up the connection so that a syslog on
this connection that fails to submit a message to Syslog writes the
message instead to system console. If off, syslog does not write
to the system console (but of course Syslog may write messages it
receives to the console).
LOG_PID
- When on,
openlog sets up the connection so that a syslog
on this connection inserts the calling process' Process ID (PID) into
the message. When off, openlog does not insert the PID.
LOG_NDELAY
- When on,
openlog opens and connects the /dev/log socket.
When off, a future syslog call must open and connect the socket.
Portability note: In early systems, the sense of this bit was
exactly the opposite.
LOG_ODELAY
- This bit does nothing. It exists for backward compatibility.
If any other bit in options is on, the result is undefined.
facility is the default facility code for this connection. A
syslog on this connection that specifies default facility causes
this facility to be associated with the message. See syslog for
possible values. A value of zero means the default default, which is
LOG_USER.
If a Syslog connection is already open when you call openlog,
openlog "reopens" the connection. Reopening is like opening
except that if you specify zero for the default facility code, the
default facility code simply remains unchanged and if you specify
LOG_NDELAY and the socket is already open and connected, openlog
just leaves it that way.
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