30.2. Writing event files with compatibilitylogger

The compatibilitylogger is a unix pipeline element that accepts old style NSCL buffers and produces an old style event file for a single run. Normally this is the end stage of a pipline consisting of ringselector, compatibilitybuffer and itself used to write event files in old spectrodaq format.

Once an end of run event is seen, the event file is closed and the program exits. Event files are segmented just as they are in both systems. Event file segments are no larger than 2Gbytes. This allows them to be properly accessed over all versions of NFS.

Since the pipelines that use compatibilitylogger are intended to be used with the ReadoutShell, event filenames match those used by the ring buffer daq rather than those used by the spectrodaq system. This allows the ReadoutShell to properly maintain the file/directory structure of the stagearea.

Below is a sample pipeline that takes as input a ring buffer event file and produces the corresponing nscl buffer event file:

Example 30-3. Using compatibilitylogger to convert event files

cd OldEventFiles
compatibilitybuffer <~/stagerea/complete/run-0123-00.evt | compatibilitylogger 

The example assumes the existence of a subdirectory OldEventFiles.