eventlog -- Record Event Data to Disk.


eventlog [options...]


Records event data verbatim from ring buffers to disk files. The program monitors the source ring buffer for a begin run item. At that point it opens an event file for that run and begins to record data from the ring.

Runs are recorded in files in the target directory. Event files are named run-runnumber-segment.evt where runnumber is the run number of the run taken from the begin run item, segment is a file segment numbered from zero.

Runs are segmented in file that are no larger than a segment size. This is done to avoid creating files that are too large for a file system to handle or too large for NFS to accurately serve.

An option allows the program to be started by a controlling program for a single run (e.g. by the readout GUI).

Options have sensible defaults. See OPTIONS below.



If present, an SHA512 checksum is computed over the data in each run and output to a file named run-nnnn.sha512 in the same directory as the event file. The checksum should match the value that would be produced by the command: sha512sum run-nnnn*.evt


Indicates to the logger the number of end of run items it should expect to see prior to closing the run. Once the first end of run is seen, if there is ever a long time without getting any data from the ring source, the logger will complain about a timeout and close the run anyway.

Once n end of run items are seen in a single run, the run file is closed. As you might expect, n must be an integer with a value that is greater than zero.


Defines the event source as a Ring buffer Uniform Resource Identifier (URI). The URI can be for a local or a remote ring buffer. By default the ring: tcp://localhost/username where username is the username of the account running the program.


Provides the path to the directory in which the program will write its event files. By default, this is current working directory at the time eventlog is started.

eventlog ensures that the path is a directory and is writable.


Specifies the size of the files segments created. size-spec can be any of an integer number of bytes or an integer followed by one of the suffixes: g, m, k that multiply the integer by a gigabyte, a megabyte and a kilobyte repsectively.

The default value is a 1900m, which should be suitable for most operating environments.


When present, the program only records a single run, then exits. The program will also create the .started file in the target directory when it's ready to record data, and the .exited file when it's about to exit.

--run number

When present, the number unconditionally sets the run number for the run. This requires the --oneshot switch to be present and eventlog will exit with an error if that is not the case. This switch is intended to be used with a set of event sources that either don't have the concept of a run number or, alternatively, cannot synchronize their run numbers. The NSCLDAQ-11 readoutGui will use this switch to force the run number of event files created to match the run number in the ReadoutGUI run number entry.


When present, the normal checks in --one-shot mode that would make the event logger exit if run numbers are observed to change or if there are too many begin runs, are not made.