logger (util-linux) sends a message to the system logger, useful for testing log routing or adding log lines from shell scripts.
logger "deploy script finished" # tagged with your username, facility user.notice
logger -t myapp -p user.info "starting nightly job" # custom tag and facility.priority
logger -p authpriv.crit "suspicious login attempt"
logger -s "also print this to stderr"
echo "line from a pipe" | logger -t mypipe
logger --journald <<EOF # write structured fields directly to journald
MESSAGE=custom structured log line
PRIORITY=6
MYAPP_FIELD=value
EOF
Check where it landed:
journalctl -t myapp --since "5 min ago"
tail -f /var/log/messages | grep myapp # traditional syslog path, if used
If nothing shows up, the facility/priority combination may be filtered by rsyslog/journald configuration, or the traditional kernel log daemon (klogd on very old systems) is not running for kernel-facility messages. Related: journalctl for reading, cron for scheduled jobs that often pipe their output through logger.