to the system message logger.
The message is then written to the system console, log files,
logged-in users, or forwarded to other machines as appropriate.
The message is identical to a
format string, except that
is replaced by the current error
(As denoted by the global variable
A trailing newline is added if none is present.
is an alternate form in which the arguments have already been captured
using the variable-length argument facilities of
The message is tagged with
Fa priority .
Priorities are encoded as a
The facility describes the part of the system
generating the message.
The level is selected from the following
(high to low) list:
A panic condition.
This is normally broadcast to all users.
A condition that should be corrected immediately, such as a corrupted
Critical conditions, e.g., hard device errors.
Conditions that are not error conditions,
but should possibly be handled specially.
Messages that contain information
normally of use only when debugging a program.
provides for more specialized processing of the messages sent
is a string that will be prepended to every message.
is a bit field specifying logging options, which is formed by
one or more of the following values:
cannot pass the message to
it will attempt to write the message to the console
Open the connection to
Normally the open is delayed until the first message is logged.
Useful for programs that need to manage the order in which file
descriptors are allocated.
Write the message to standard error output as well to the system log.
Log the process id with each message: useful for identifying
instantiations of daemons.
argument encodes a default facility to be assigned to all messages
that do not have an explicit facility encoded:
Messages generated by random user processes.
This is the default facility identifier if none is specified.
The uucp system.
Reserved for local use.
can be used to close the log file.
sets the log priority mask to
and returns the previous mask.
with a priority not set in
The mask for an individual priority
is calculated by the macro
LOG_MASK (pri ;);
the mask for all priorities up to and including
is given by the macro
LOG_UPTO (toppri ; .);
The default allows all priorities to be logged.
return no value.
always returns the previous log mask level.
Never pass a string with user-supplied data as a format without using
An attacker can put format specifiers in the string to mangle your stack,
leading to a possible security hole.
This holds true even if the string was built using a function like
as the resulting string may still contain user-supplied conversion specifiers
for later interpolation by