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:
Print a short help text and exit.
Print a short version string and exit.
Specify a short string that is used to identify the
logging tool. If not specified, no identification string is written to the
Specify the default priority level for the logged
messages. Pass one of "emerg", "alert", "crit",
"err", "warning", "notice", "info",
"debug", or a value between 0 and 7 (corresponding to the same named
levels). These priority values are the same as defined by syslog(3)
Defaults to "info". Note that this simply controls the default,
individual lines may be logged with different levels if they are prefixed
accordingly. For details, see --level-prefix=
Specifies the default priority level for messages from
the process's standard error output (stderr). Usage of this option is the same
as the --priority=
option, above, and both can be used at once. When
both are used, --priority=
will specify the default priority for
standard output (stdout).
If --stderr-priority= is not specified, messages from
stderr will still be logged, with the same default priority level as
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.
Controls whether lines read are parsed for syslog
priority level prefixes. If enabled (the default), a line prefixed with a
priority prefix such as "<5>" is logged at priority 5
("notice"), and similar for the other priority levels. Takes a
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
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:
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