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PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface
may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface
may not be implemented on Linux.
NAME
syslog.h — definitions for system error logging
SYNOPSIS
#include <syslog.h>
DESCRIPTION
The <syslog.h> header shall define the following symbolic constants, zero or more of which may be OR'ed
together to form the logopt option of openlog():
LOG_PID Log the process ID with each message.
LOG_CONS Log to the system console on error.
LOG_NDELAY Connect to syslog daemon immediately.
LOG_ODELAY Delay open until syslog() is called.
LOG_NOWAIT Do not wait for child processes.
The <syslog.h> header shall define the following symbolic constants for use as the facility argument to
openlog():
LOG_KERN Reserved for message generated by the system.
LOG_USER Message generated by a process.
LOG_MAIL Reserved for message generated by mail system.
LOG_NEWS Reserved for message generated by news system.
LOG_UUCP Reserved for message generated by UUCP system.
LOG_DAEMON Reserved for message generated by system daemon.
LOG_AUTH Reserved for message generated by authorization daemon.
LOG_CRON Reserved for message generated by clock daemon.
LOG_LPR Reserved for message generated by printer system.
LOG_LOCAL0 Reserved for local use.
LOG_LOCAL1 Reserved for local use.
LOG_LOCAL2 Reserved for local use.
LOG_LOCAL3 Reserved for local use.
LOG_LOCAL4 Reserved for local use.
LOG_LOCAL5 Reserved for local use.
LOG_LOCAL6 Reserved for local use.
LOG_LOCAL7 Reserved for local use.
The <syslog.h> header shall define the following macros for constructing the maskpri argument to
setlogmask(). The following macros expand to an expression of type int when the argument pri is an
expression of type int:
LOG_MASK(pri) A mask for priority pri.
The <syslog.h> header shall define the following symbolic constants for use as the priority argument of
syslog():
LOG_EMERG A panic condition was reported to all processes.
LOG_ALERT A condition that should be corrected immediately.
LOG_CRIT A critical condition.
LOG_ERR An error message.
LOG_WARNING A warning message.
LOG_NOTICE A condition requiring special handling.
LOG_INFO A general information message.
LOG_DEBUG A message useful for debugging programs.
The following shall be declared as functions and may also be defined as macros. Function prototypes shall
be provided.
void closelog(void);
void openlog(const char *, int, int);
int setlogmask(int);
void syslog(int, const char *, ...);
The following sections are informative.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
The System Interfaces volume of POSIX.1‐2017, closelog()
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original
IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document.
The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page are most likely to have been introduced
during the conversion of the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .