`logger`

Make entries in the system log (POSIX)

If you aren't root, specify the full path: /usr/sbin/logger.

Syntax:

logger [-is] [-f file] [-p pri] [-t tag] 
       [message ...]

Neutrino

-f file: Log the specified file.
-i: Log the process ID of the logger process with each line.
-p pri: Enter the message with the specified priority. The priority may be specified numerically or as a facility.level pair. For example, -p local3.info logs the message(s) as informational level in the local3 facility. The default is user.notice.
-s: Log the message to standard error, as well as the system log.
-t tag: Mark every line in the log with the specified tag.
message: Write the message to log; if not specified, and the -f flag isn't provided, standard input is logged.

The logger command provides a shell command interface to the syslogd daemon.

Log the message "System rebooted":

logger System rebooted

Log the file /tmp/log tagging each line with log:

logger -f /tmp/log -t log

/usr/sbin/logger: The logger utility is located in the /usr/sbin/ directory, which is not included in the default PATH of non-root users. If you are not root, specify the full path.

SYSLOG: When defined, SYSLOG specifies which node syslogd is running on. By default, the local node is assumed.

Because the syslog API doesn't return error codes, only argument errors can be detected.