systemd-cat
Send command output to the systemd journal
TLDR
Write the output of the specified command to the journal (both output streams are captured)
Write the output of a pipeline to the journal (stderr stays connected to the terminal)
Use the specified identifier (default: cat when reading from a pipeline, executable name otherwise)
Use the specified default priority level for all logged messages
Use the specified default priority level for the logged messages from the command's stderr
SYNOPSIS
systemd-cat [OPTIONS...] [FILES...]
PARAMETERS
--all, -a
Displays all journal fields, including internal and less commonly shown ones.
--quiet, -q
Suppresses informational messages and empty lines, producing a cleaner output.
--output=FORMAT, -o FORMAT
Specifies the output format. Common formats include short (default), verbose, json, json-pretty, among others.
--help, -h
Shows a help message and exits.
--version
Shows version information and exits.
FILES...
One or more paths to journal files or directories to be concatenated and displayed. If no files are specified, it reads from standard input.
DESCRIPTION
systemd-cat is a utility designed to concatenate and print entries from the systemd journal. It offers a simpler, cat-like interface compared to journalctl, which is the primary tool for querying and displaying the live journal.
systemd-cat is particularly useful for processing journal data from specific journal files or directories, or when piping journal entries from standard input. While it doesn't offer the extensive filtering and live monitoring capabilities of journalctl, it excels at presenting journal content in a straightforward, stream-oriented manner. It can display various structured journal fields alongside the main log message, providing valuable context. The command is often employed when you need to treat journal data like any other text stream, enabling easy integration with standard Unix text processing tools.
CAVEATS
systemd-cat is less powerful than journalctl for live querying or complex filtering of the active journal. It is primarily designed for concatenating existing journal files or standard input, not for real-time log analysis with advanced filtering capabilities.
INPUT SOURCES
systemd-cat can read journal entries from specified journal files, directories, or standard input. When invoked without FILES, it reads from standard input, expecting journal entries in a format that it can parse (e.g., from journalctl --output=export).
OUTPUT FORMATS
The --output option is crucial for controlling how journal entries are presented. For example, short provides a traditional log-like output, verbose adds more fields for debugging, and json or json-pretty are useful for programmatic processing and integration with other tools.
HISTORY
systemd-cat was introduced as part of the systemd suite, which aimed to modernize the Linux init system and provide a comprehensive set of tools for system management. It offers a familiar cat-like interface for journal entries, complementing journalctl's more robust querying capabilities. Its design reflects the systemd philosophy of offering specialized, composable tools for specific tasks related to system logging and management.
SEE ALSO
journalctl(1), cat(1), systemd(1), systemd-journald(8)
