# LOGGER - enter messages into the system log - man - [phpMan] > **TLDR:** Add messages to syslog. > - Log a message to syslog: `logger {{message}}` *Source: tldr-pages* --- [_LOGGER_(1)](https://www.chedong.com/phpMan.php/man/LOGGER/1/markdown) User Commands [_LOGGER_(1)](https://www.chedong.com/phpMan.php/man/LOGGER/1/markdown) ## NAME logger - enter messages into the system log ## SYNOPSIS **logger **[options] _message_ ## DESCRIPTION **logger **makes entries in the system log. When the optional _message_ argument is present, it is written to the log. If it is not present, and the **-f **option is not given either, then standard input is logged. ## OPTIONS ### -d --udp Use datagrams (UDP) only. By default the connection is tried to the syslog port defined in _/etc/services_, which is often 514. See also **--server **and **--socket **to specify where to connect. ### -e --skip-empty Ignore empty lines when processing files. An empty line is defined to be a line without any characters. Thus a line consisting only of whitespace is NOT considered empty. Note that when the **--prio-prefix **option is specified, the priority is not part of the line. Thus an empty line in this mode is a line that does not have any characters after the priority prefix (e.g., **<13>**). ### -f --file _ Log the contents of the specified _file_. This option cannot be combined with a command-line message. ### -i Log the PID of the **logger **process with each line. **--id**[**=_**id_] Log the PID of the **logger **process with each line. When the optional argument _id_ is specified, then it is used instead of the **logger **command’s PID. The use of **--id=$$ **(PPID) is recommended in scripts that send several messages. Note that the system logging infrastructure (for example **systemd **when listening on _/dev/log_) may follow local socket credentials to overwrite the PID specified in the message. [**logger**(1)](https://www.chedong.com/phpMan.php/man/logger/1/markdown) is able to set those socket credentials to the given _id_, but only if you have root permissions and a process with the specified PID exists, otherwise the socket credentials are not modified and the problem is silently ignored. **--journald**[**=_**file_] Write a **systemd **journal entry. The entry is read from the given _file_, when specified, otherwise from standard input. Each line must begin with a field that is accepted by **journald**; see [**systemd.journal-fields**(7)](https://www.chedong.com/phpMan.php/man/systemd.journal-fields/7/markdown) for details. The use of a MESSAGE_ID field is generally a good idea, as it makes finding entries easy. Examples: logger --journald <> MSGID field. Note that the space character is not permitted inside of _msgid_. This option is only used if **--rfc5424 **is specified as well; otherwise, it is silently ignored. ### -n --server _ Write to the specified remote syslog _server_ instead of to the system log socket. Unless **--udp **or **--tcp **is specified, **logger **will first try to use UDP, but if this fails a TCP connection is attempted. ### --no-act Causes everything to be done except for writing the log message to the system log, and removing the connection to the journal. This option can be used together with **--stderr** for testing purposes. ### --octet-count Use the RFC 6587 <> octet counting framing method for sending messages. When this option is not used, the default is no framing on UDP, and RFC6587 non-transparent framing (also known as octet stuffing) on TCP. ### -P --port _ Use the specified _port_. When this option is not specified, the port defaults to **syslog** for udp and to **syslog-conn **for tcp connections. ### -p --priority _ Enter the message into the log with the specified _priority_. The priority may be specified numerically or as a _facility_._level_ pair. For example, **-p local3.info **logs the message as informational in the local3 facility. The default is **user.notice**. ### --prio-prefix Look for a syslog prefix on every line read from standard input. This prefix is a decimal number within angle brackets that encodes both the facility and the level. The number is constructed by multiplying the facility by 8 and then adding the level. For example, **local0.info**, meaning facility=16 and level=6, becomes **<134>**. If the prefix contains no facility, the facility defaults to what is specified by the **-p** option. Similarly, if no prefix is provided, the line is logged using the _priority_ given with **-p**. This option doesn’t affect a command-line message. ### --rfc3164 Use the RFC 3164 <> BSD syslog protocol to submit messages to a remote server. **--rfc5424**[**=_**without_] Use the RFC 5424 <> syslog protocol to submit messages to a remote server. The optional _without_ argument can be a comma-separated list of the following values: **notq**, **notime**, **nohost**. The **notq **value suppresses the time-quality structured data from the submitted message. The time-quality information shows whether the local clock was synchronized plus the maximum number of microseconds the timestamp might be off. The time quality is also automatically suppressed when **--sd-id timeQuality **is specified. The **notime **value (which implies **notq**) suppresses the complete sender timestamp that is in ISO-8601 format, including microseconds and timezone. The **nohost **value suppresses [**gethostname**(2)](https://www.chedong.com/phpMan.php/man/gethostname/2/markdown) information from the message header. The RFC 5424 protocol has been the default for **logger **since version 2.26. ### -s --stderr Output the message to standard error as well as to the system log. **--sd-id _**name_[**@_**digits_] Specifies a structured data element ID for an RFC 5424 message header. The option has to be used before **--sd-param **to introduce a new element. The number of structured data elements is unlimited. The ID (_name_ plus possibly **@_**digits_) is case-sensitive and uniquely identifies the type and purpose of the element. The same ID must not exist more than once in a message. The **@_**digits_ part is required for user-defined non-standardized IDs. **logger **currently generates the **timeQuality **standardized element only. RFC 5424 also describes the elements **origin **(with parameters **ip**, **enterpriseId**, **software **and **swVersion**) and **meta **(with parameters **sequenceId**, **sysUpTime **and **language**). These element IDs may be specified without the **@_**digits_ suffix. **--sd-param _**name_=_value_ Specifies a structured data element parameter, a name and value pair. The option has to be used after **--sd-id **and may be specified more than once for the same element. Note that the quotation marks around _value_ are required and must be escaped on the command line. logger --rfc5424 --sd-id zoo@123 \ --sd-param tiger="hungry" \ --sd-param zebra="running" \ --sd-id manager@123 \ --sd-param onMeeting="yes" \ "this is message" produces: **<13>1 2015-10-01T14:07:59.168662+02:00 ws kzak - - [timeQuality tzKnown="1" isSynced="1"** **syncAccuracy="218616"][zoo@123 tiger="hungry" zebra="running"][manager@123** **onMeeting="yes"] this is message** ### -S --size _ Sets the maximum permitted message size to _size_. The default is 1KiB characters, which is the limit traditionally used and specified in RFC 3164. With RFC 5424, this limit has become flexible. A good assumption is that RFC 5424 receivers can at least process 4KiB messages. Most receivers accept messages larger than 1KiB over any type of syslog protocol. As such, the **--size **option affects **logger **in all cases (not only when **--rfc5424 **was used). Note: the message-size limit limits the overall message size, including the syslog header. Header sizes vary depending on the selected options and the hostname length. As a rule of thumb, headers are usually not longer than 50 to 80 characters. When selecting a maximum message size, it is important to ensure that the receiver supports the max size as well, otherwise messages may become truncated. Again, as a rule of thumb two to four KiB message size should generally be OK, whereas anything larger should be verified to work. **--socket-errors**[**=_**mode_] Print errors about Unix socket connections. The _mode_ can be a value of **off**, **on**, or **auto**. When the mode is **auto**, then **logger **will detect if the init process is [**systemd**(1)](https://www.chedong.com/phpMan.php/man/systemd/1/markdown), and if so assumption is made _/dev/log_ can be used early at boot. Other init systems lack of _/dev/log_ will not cause errors that is identical with messaging using [**openlog**(3)](https://www.chedong.com/phpMan.php/man/openlog/3/markdown) system call. The [**logger**(1)](https://www.chedong.com/phpMan.php/man/logger/1/markdown) before version 2.26 used [**openlog**(3)](https://www.chedong.com/phpMan.php/man/openlog/3/markdown), and hence was unable to detected loss of messages sent to Unix sockets. The default mode is **auto**. When errors are not enabled lost messages are not communicated and will result to successful exit status of [**logger**(1)](https://www.chedong.com/phpMan.php/man/logger/1/markdown) invocation. ### -T --tcp Use stream (TCP) only. By default the connection is tried to the _syslog-conn_ port defined in _/etc/services_, which is often _601_. See also **--server **and **--socket **to specify where to connect. ### -t --tag _ Mark every line to be logged with the specified _tag_. The default tag is the name of the user logged in on the terminal (or a user name based on effective user ID). ### -u --socket _ Write to the specified _socket_ instead of to the system log socket. **--** End the argument list. This allows the _message_ to start with a hyphen (-). ### -h --help Display help text and exit. ### -V --version Print version and exit. ## EXIT STATUS The **logger **utility exits 0 on success, and >0 if an error occurs. ## FACILITIES AND LEVELS Valid facility names are: ### auth **authpriv **for security information of a sensitive nature ### cron ### daemon ### ftp **kern **cannot be generated from userspace process, automatically converted to **user** ### lpr ### mail ### news ### syslog ### user ### uucp ### local0 to ### local7 **security **deprecated synonym for **auth** Valid level names are: ### emerg ### alert ### crit ### err ### warning ### notice ### info ### debug **panic **deprecated synonym for **emerg** **error **deprecated synonym for **err** **warn **deprecated synonym for **warning** For the priority order and intended purposes of these facilities and levels, see [**syslog**(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown). ## CONFORMING TO The **logger **command is expected to be IEEE Std 1003.2 ("POSIX.2") compatible. ## EXAMPLES logger System rebooted logger -p local0.notice -t HOSTIDM -f /dev/idmc logger -n loghost.example.com System rebooted ## AUTHORS The **logger **command was originally written by University of California in 1983-1993 and later rewritten by Karel Zak <>, Rainer Gerhards <>, and Sami Kerola <>. ## SEE ALSO [**journalctl**(1)](https://www.chedong.com/phpMan.php/man/journalctl/1/markdown), [**syslog**(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown), [**systemd.journal-fields**(7)](https://www.chedong.com/phpMan.php/man/systemd.journal-fields/7/markdown) ## REPORTING BUGS For bug reports, use the issue tracker at . ## AVAILABILITY The **logger **command is part of the util-linux package which can be downloaded from Linux Kernel Archive <>. util-linux 2.39.3 2023-11-21 [_LOGGER_(1)](https://www.chedong.com/phpMan.php/man/LOGGER/1/markdown)