closelog(3c)

1syslog(3C)               Standard C Library Functions               syslog(3C)
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NAME

6       syslog, openlog, closelog, setlogmask - control system log
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SYNOPSIS

9       #include <syslog.h>
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11       void openlog(const char *ident, int logopt, int facility);
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14       void syslog(int priority, const char *message, .../* arguments */);
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17       void closelog(void);
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20       int setlogmask(int maskpri);
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DESCRIPTION

24       The  syslog() function sends a message to syslogd(1M), which, depending
25       on the configuration of /etc/syslog.conf, logs  it  in  an  appropriate
26       system  log,  writes it to the system console, forwards it to a list of
27       users, or forwards it to syslogd on another host over the network.  The
28       logged  message includes a message header and a message body.  The mes‐
29       sage header consists of a facility indicator, a severity level  indica‐
30       tor, a timestamp, a tag string, and optionally the process ID.
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33       The  message body is generated from the message and following arguments
34       in the same manner as if these were arguments to  printf(3UCB),  except
35       that  occurrences  of %m in the format string pointed to by the message
36       argument are replaced by the error message string associated  with  the
37       current  value  of  errno.   A  trailing  NEWLINE character is added if
38       needed.
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41       Symbolic constants for use as values of the logopt, facility, priority,
42       and maskpri arguments are defined in the <syslog.h> header.
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45       Values of the priority argument are formed by ORing together a severity
46       level value and an optional facility value.  If no  facility  value  is
47       specified, the current default facility value is used.
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50       Possible values of severity level include, in decreasing order:
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52       LOG_EMERG      A  panic  condition.   This is normally broadcast to all
53                      users.
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56       LOG_ALERT      A condition that should be corrected  immediately,  such
57                      as a corrupted system database.
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60       LOG_CRIT       Critical conditions, such as hard device errors.
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63       LOG_ERR        Errors.
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66       LOG_WARNING    Warning messages.
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69       LOG_NOTICE     Conditions  that  are not error conditions, but that may
70                      require special handling.
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73       LOG_INFO       Informational messages.
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76       LOG_DEBUG      Messages that contain information normally of  use  only
77                      when debugging a program.
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81       The  facility  indicates the application or system component generating
82       the message.  Possible facility values include:
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84       LOG_KERN      Messages generated by the kernel. These cannot be  gener‐
85                     ated by any user processes.
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88       LOG_USER      Messages  generated by random user processes. This is the
89                     default facility identifier if none is specified.
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92       LOG_MAIL      The mail system.
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95       LOG_DAEMON    System daemons, such as in.ftpd(1M).
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98       LOG_AUTH      The authentication /  security  /  authorization  system:
99                     login(1), su(1M), getty(1M).
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102       LOG_LPR       The line printer spooling system: lpr(1B), lpc(1B).
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105       LOG_NEWS      Designated for the USENET network news system.
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108       LOG_UUCP      Designated for the UUCP system; it does not currently use
109                     syslog().
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112       LOG_CRON      The cron/at facility; crontab(1), at(1), cron(1M).
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115       LOG_AUDIT     The audit facility, for example, auditd(1M).
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118       LOG_LOCAL0    Designated for local use.
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121       LOG_LOCAL1    Designated for local use.
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124       LOG_LOCAL2    Designated for local use.
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127       LOG_LOCAL3    Designated for local use.
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130       LOG_LOCAL4    Designated for local use.
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133       LOG_LOCAL5    Designated for local use.
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136       LOG_LOCAL6    Designated for local use.
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139       LOG_LOCAL7    Designated for local use.
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143       The openlog() function sets process attributes that  affect  subsequent
144       calls  to syslog(). The ident argument is a string that is prepended to
145       every message. The openlog() function uses the passed-in ident argument
146       directly,  rather than making a private copy of it. The logopt argument
147       indicates logging options.  Values for logopt are constructed by a bit‐
148       wise-inclusive OR of zero or more of the following:
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150       LOG_PID       Log the process ID with each message.  This is useful for
151                     identifying specific daemon processes (for  daemons  that
152                     fork).
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155       LOG_CONS      Write  messages  to  the system console if they cannot be
156                     sent to syslogd(1M). This option is safe to use in daemon
157                     processes  that  have no controlling terminal, since sys‐
158                     log() forks before opening the console.
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161       LOG_NDELAY    Open the connection to syslogd(1M) immediately.  Normally
162                     the  open  is  delayed until the first message is logged.
163                     This is useful for programs that need to manage the order
164                     in which file descriptors are allocated.
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167       LOG_ODELAY    Delay open until syslog() is called.
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170       LOG_NOWAIT    Do  not wait for child processes that have been forked to
171                     log messages onto the console.   This  option  should  be
172                     used  by processes that enable notification of child ter‐
173                     mination using  SIGCHLD,  since  syslog()  may  otherwise
174                     block  waiting  for a child whose exit status has already
175                     been collected.
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179       The facility argument encodes a default facility to be assigned to  all
180       messages  that  do  not have an explicit facility already encoded.  The
181       initial default facility is LOG_USER.
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184       The openlog() and syslog() functions may allocate  a  file  descriptor.
185       It is not necessary to call openlog() prior to calling syslog().
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188       The  closelog()  function closes any open file descriptors allocated by
189       previous calls to openlog() or syslog().
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192       The setlogmask() function sets the log priority mask  for  the  current
193       process to maskpri and returns the previous mask.  If the maskpri argu‐
194       ment is 0, the current log mask is not modified.  Calls by the  current
195       process  to  syslog()  with a priority not set in maskpri are rejected.
196       The mask for an individual priority pri  is  calculated  by  the  macro
197       LOG_MASK(pri);  the  mask for all priorities up to and including toppri
198       is given by the macro LOG_UPTO(toppri). The default log mask allows all
199       priorities to be logged.
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RETURN VALUES

202       The  setlogmask()  function returns the previous log priority mask. The
203       closelog(), openlog() and syslog() functions return no value.
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ERRORS

206       No errors are defined.
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EXAMPLES

209       Example 1 Example of LOG_ALERT message.
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212       This call logs a message at priority LOG_ALERT:
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215         syslog(LOG_ALERT, "who: internal error 23");
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220       The FTP daemon ftpd would make this call to openlog() to indicate  that
221       all  messages it logs should have an identifying string of ftpd, should
222       be treated by syslogd(1M) as other messages from  system  daemons  are,
223       should include the process ID of the process logging the message:
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226         openlog("ftpd", LOG_PID, LOG_DAEMON);
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231       Then  it would make the following call to setlogmask() to indicate that
232       messages at priorities from LOG_EMERG through LOG_ERR should be logged,
233       but that no messages at any other priority should be logged:
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236         setlogmask(LOG_UPTO(LOG_ERR));
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241       Then,  to log a message at priority LOG_INFO, it would make the follow‐
242       ing call to syslog:
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245         syslog(LOG_INFO, "Connection from host %d", CallingHost);
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250       A locally-written utility could use the following call to  syslog()  to
251       log  a  message  at  priority  LOG_INFO to be treated by syslogd(1M) as
252       other messages to the facility  LOG_LOCAL2 are:
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255         syslog(LOG_INFO|LOG_LOCAL2, "error: %m");
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ATTRIBUTES

260       See attributes(5) for descriptions of the following attributes:
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265       ┌─────────────────────────────┬─────────────────────────────┐
266       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
267       ├─────────────────────────────┼─────────────────────────────┤
268       │Interface Stability          │Committed                    │
269       ├─────────────────────────────┼─────────────────────────────┤
270       │MT-Level                     │Safe                         │
271       ├─────────────────────────────┼─────────────────────────────┤
272       │Standard                     │See standards(5).            │
273       └─────────────────────────────┴─────────────────────────────┘
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