table of contents
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|SYSLOG(3)||Linux Programmer's Manual||SYSLOG(3)|
NAME¶closelog, openlog, syslog, vsyslog - send messages to the system logger
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
DESCRIPTION¶closelog() closes the descriptor being used to write to the system logger. The use of closelog() is optional.
option¶The option argument to openlog() is an OR of any of these:
- Write directly to system console if there is an error while sending to system logger.
- Open the connection immediately (normally, the connection is opened when the first message is logged).
- Don't wait for child processes that may have been created while logging the message. (The GNU C library does not create a child process, so this option has no effect on Linux.)
- The converse of LOG_NDELAY; opening of the connection is delayed until syslog() is called. (This is the default, and need not be specified.)
- (Not in POSIX.1-2001 or POSIX.1-2008.) Print to stderr as well.
- Include PID with each message.
facility¶The facility argument is used to specify what type of program is logging the message. This lets the configuration file specify that messages from different facilities will be handled differently.
- security/authorization messages
- security/authorization messages (private)
- clock daemon (cron and at)
- system daemons without separate facility value
- ftp daemon
- kernel messages (these can't be generated from user processes)
- LOG_LOCAL0 through LOG_LOCAL7
- reserved for local use
- line printer subsystem
- mail subsystem
- USENET news subsystem
- messages generated internally by syslogd(8)
- LOG_USER (default)
- generic user-level messages
- UUCP subsystem
level¶This determines the importance of the message. The levels are, in order of decreasing importance:
- system is unusable
- action must be taken immediately
- critical conditions
- error conditions
- warning conditions
- normal, but significant, condition
- informational message
- debug-level message
CONFORMING TO¶The functions openlog(), closelog(), and syslog() (but not vsyslog()) are specified in SUSv2, POSIX.1-2001, and POSIX.1-2008. POSIX.1-2001 specifies only the LOG_USER and LOG_LOCAL* values for facility. However, with the exception of LOG_AUTHPRIV and LOG_FTP, the other facility values appear on most UNIX systems. The LOG_PERROR value for option is not specified by POSIX.1-2001 or POSIX.1-2008, but is available in most versions of UNIX.
NOTES¶The argument ident in the call of openlog() is probably stored as-is. Thus, if the string it points to is changed, syslog() may start prepending the changed string, and if the string it points to ceases to exist, the results are undefined. Most portable is to use a string constant. Never pass a string with user-supplied data as a format, use the following instead:
syslog(priority, "%s", string);
SEE ALSO¶logger(1), setlogmask(3), syslog.conf(5), syslogd(8)
COLOPHON¶This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.