gno/usr.man/man3/syslog.3

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.TH SYSLOG 3 "28 January 1997" GNO "Library Routines"
.SH NAME
.BR syslog ,
.BR vsyslog ,
.BR syslogmt ,
.BR vsyslogmt ,
.BR openlog ,
.BR closelog ,
.BR setlogmask
\- control system log
.SH SYNOPSIS
#include <syslog.h>
.br
#include <varargs.h>
.sp 1
void
\fBsyslog\fR (int \fIpriority\fR, const char *\fImessage\fR, ...);
.br
void
\fBvsyslog\fR (int \fIpriority\fR, const char *\fImessage\fR,
va_list \fBargs\fR);
.br
void
\fBsyslogmt\fR (int \fIpriority\fR, const char *\fImessage\fR, ...);
.br
void
\fBvsyslogmt\fR (int \fIpriority\fR, const char *\fImessage\fR,
va_list \fBargs\fR);
.br
void
\fBopenlog\fR (const char *\fIident\fR, int \fIlogopt\fR, int \fIfacility\fR);
.br
void
\fBcloselog\fR (void);
.br
int
\fBsetlogmask\fR (int \fImaskpri\fR);
.SH DESCRIPTION
The
.BR syslog 
function
writes
.I message
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. (See
.BR syslogd (8).)
.LP
The message is identical to a
.BR printf (3)
format string, except that
.BR %m
is replaced by the current error
message. (As denoted by the global variable
.IR errno ;
see
.BR strerror (3).)
A trailing newline is added if none is present.
.LP
The
.BR vsyslog 
function
is an alternate form in which the arguments have already been captured
using the variable-length argument facilities of
.BR varargs (3).
.LP
The
.BR syslogmt
and
.BR vsyslogmt
are multithread-safe variants of the
.BR syslog
and
.BR vsyslog
routines.  Note that the permissable list of format specifiers for these
two routines is much smaller than those for 
.BR syslog
or
.BR vsyslog .
The full list of format specifiers is given in the
.BR sprintmt (3)
manual page.
These two routines are GNO-specific and therefore non-portable.
.LP
The message is tagged with
.IR priority .
Priorities are encoded as a
.I facility
and a
.IR level .
The facility describes the part of the system
generating the message.
The level is selected from the following
.IR ordered 
(high to low) list:
.RS
.IP "\fBLOG_EMERG\fR"
A panic condition.
This is normally broadcast to all users.
.IP "\fBLOG_ALERT\fR"
A condition that should be corrected immediately, such as a corrupted
system database.
.IP "\fBLOG_CRIT\fR"
Critical conditions, e.g., hard device errors.
.IP "\fBLOG_ERR\fR"
Errors.
.IP "\fBLOG_WARNING\fR"
Warning messages.
.IP "\fBLOG_NOTICE\fR"
Conditions that are not error conditions,
but should possibly be handled specially.
.IP "\fBLOG_INFO\fR"
Informational messages.
.IP "\fBLOG_DEBUG\fR"
Messages that contain information
normally of use only when debugging a program.
.RE
.LP
The
.BR openlog 
function
provides for more specialized processing of the messages sent
by
.BR syslog 
and
.BR vsyslog .
The parameter
.I ident
is a string that will be prepended to every message.
The
.I logopt
argument
is a bit field specifying logging options, which is formed by
.BR OR 'ing
one or more of the following values:
.RS
.IP "\fBLOG_CONS\fR"
If
.BR syslog 
cannot pass the message to
.BR syslogd (8)
it will attempt to write the message to the console
.BR .ttyco .
.IP "\fBLOG_NDELAY\fR"
Open the connection to
.BR syslogd (8)
immediately.
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.
.IP "\fBLOG_PERROR\fR"
Write the message to standard error output as well to the system log.
.IP "\fBLOG_PID\fR"
Log the process id with each message: useful for identifying
instantiations of daemons.
.RE
.LP
The
.I facility
parameter encodes a default facility to be assigned to all messages
that do not have an explicit facility encoded:
.RS
.IP "\fBLOG_AUTH\fR"
The authorization system:
.BR login (1),
.BR su (1),
.BR getty (8),
etc.
.IP "\fBLOG_AUTHPRIV\fR"
The same as
.BR LOG_AUTH ,
but logged to a file readable only by
selected individuals.
.IP "\fBLOG_CRON\fR"
The cron daemon:
.BR cron (8).
.IP "\fBLOG_DAEMON\fR"
System daemons, such as
.BR routed (8),
that are not provided for explicitly by other facilities.
.IP "\fBLOG_FTP\fR"
The file transfer protocol daemon:
.BR ftpd (8).
.IP "\fBLOG_KERN\fR"
Messages generated by the kernel.
These cannot be generated by any user processes.
.IP "\fBLOG_LPR\fR"
The line printer spooling system:
.BR lpr (1),
.BR lpc (8),
.BR lpd (8),
etc.
.IP "\fBLOG_MAIL\fR"
The mail system.
.IP "\fBLOG_NEWS\fR"
The network news system.
.IP "\fBLOG_SYSLOG\fR"
Messages generated internally by
.BR syslogd (8).
.IP "\fBLOG_USER\fR"
Messages generated by random user processes.
This is the default facility identifier if none is specified.
.IP "\fBLOG_UUCP\fR"
The uucp system.
.IP "\fBLOG_LOCAL0\fR"
Reserved for local use.
Similarly for
.BR LOG_LOCAL1
through
.BR LOG_LOCAL7 .
.RE 
.LP
The
.BR closelog 
function
can be used to close the log file.
.LP
The
.BR setlogmask 
function
sets the log priority mask to
.I maskpri
and returns the previous mask.
Calls to
.BR syslog 
with a priority not set in
.I maskpri
are rejected.
The mask for an individual priority
.I pri
is calculated by the macro \fBLOG_MASK\fR(\fIpri\fR);
the mask for all priorities up to and including
.I toppri
is given by the macro \fBLOG_UPTO\fR(\fItoppri\fR);.
The default allows all priorities to be logged.
.SH RETURN VALUES
The routines
.BR closelog ,
.BR openlog ,
.BR syslog 
and
.BR vsyslog 
return no value.
.LP
The routine
.BR setlogmask 
always returns the previous log mask level.
.SH EXAMPLES
.nf
syslog(LOG_ALERT, "who: internal error 23");

openlog("ftpd", LOG_PID | LOG_NDELAY, LOG_FTP);

setlogmask(LOG_UPTO(LOG_ERR));

syslog(LOG_INFO, "Connection from host %d", CallingHost);

syslog(LOG_INFO|LOG_LOCAL2, "foobar error: %m");
.fi
.SH MT STATUS
.BR syslogmt 
and
.BR vsyslogmt
are thread safe; the remainder are not.
.BR openlog 
should be called in the parent thread before creating the child threads.
This will ensure that any generated messages are properly tagged with
.IR ident .
.SH SEE ALSO
.BR logger (1),
.BR sprintmt (3),
.BR syslogd (8)
.SH HISTORY
These
functions appeared in 4.2BSD.