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Communications Directory

MSP communications are opened between tasks by name. The name lookup is provided by each task making an entry in a directory pointed to by the environment variable ADAM_USER. If ADAM_USER is not defined when a task attempts to register itself with the message system, directory ~/adam will be used and, if the specified directory does not exist, an attempt will be made to create it.

This results in a file being created in the ADAM_USER directory with a name compounded of the task name and an identifying number (e.g $ADAM_USER/slave_5001). Another task can then open communications by searching ADAM_USER for the right name and using the identifying number.

When a task exits, the AMS exit handler de-registers the task from MSP and the task's file is removed from ADAM_USER. If the task does not exit normally for some reason, the file in ADAM_USER may get left behind. In this case the file must be deleted explicitly; otherwise the task will refuse to load next time.



next up previous 199
Next: MSP Messages
Up: Implementation
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AMS The Unix ADAM Message System
Starlink User Note 241
B D Kelly (ROE)
A J Chipperfield (RAL)
16 August 2001
E-mail:ussc@star.rl.ac.uk

Copyright © 2000 Council for the Central Laboratory of the Research Councils