systemd-cat - Connect a pipeline or program's output with the journal
systemd-cat may be used to connect the standard input and output of a process to the journal, or as a filter tool in a shell pipeline to pass the output the previous pipeline element generates to the journal.
If no parameter is passed, systemd-cat will write everything it reads from standard input (stdin) to the journal.
If parameters are passed, they are executed as command line with standard output (stdout) and standard error output (stderr) connected to the journal, so that all it writes is stored in the journal.
The following options are understood:
If --stderr-priority= is not specified, messages from stderr will still be logged, with the same default priority level as stdout.
Also, note that when stdout and stderr use the same default priority, the messages will be strictly ordered, because one channel is used for both. When the default priority differs, two channels are used, and so stdout messages will not be strictly ordered with respect to stderr messages - though they will tend to be approximately ordered.
On success, 0 is returned, a non-zero failure code otherwise.
Example 1. Invoke a program
This calls /bin/ls with standard output and error connected to the journal:
# systemd-cat ls
Example 2. Usage in a shell pipeline
This builds a shell pipeline also invoking /bin/ls and writes the output it generates to the journal:
# ls | systemd-cat
Even though the two examples have very similar effects, the first is preferable, since only one process is running at a time and both stdout and stderr are captured, while in the second example, only stdout is captured.