Experimental Physics and
Industrial Control System

Simon Rose via Tech-talk <tech-talk at aps.anl.gov> · Thu, 16 Dec 2021 08:34:50 +0000

Hello -

In e3, the database files that are installed with a module will always be installed at the location $(module_DB) (an environment variable set by require when loading a module).

In general the e3 team at ESS recommends referencing the database file paths explicitly as opposed to relying on or manipulating EPICS_DB_INCLUDE_PATH; given that there are many modules installed together, it seems you could end up loading the "wrong" one in a possibly annoying to trace way.

Similarly, if database files are located relative to the current startup command, it would be best to explicitly reference the file as

dbLoadRecords($(E3_CMD_TOP)/path/to/database.db)

so as to remove ambiguity.

Cheers,

Simon Rose

On 2021-12-15, 18:52, "Tech-talk on behalf of Michael Davidsaver via Tech-talk" <tech-talk-bounces at aps.anl.gov on behalf of tech-talk at aps.anl.gov> wrote:

    On 12/15/21 4:35 AM, Ralph Lange via Tech-talk wrote:
    > On Wed, 15 Dec 2021 at 07:52, Alfio Rizzo via Tech-talk <tech-talk at aps.anl.gov <mailto:tech-talk at aps.anl.gov>> wrote:
    > 
    >     So my conclusion is that giving this limitation of 256 chars of maclib parser,
    >     It is wise then to never use EPICS_DB_INCLUDE_PATH in a snippet to add
    >     local db path, since if you have a long list of require you may hit into trouble.
    > 
    >  
    > So, indirectly, this is related to ESS's E3 development environment that keeps all dependency modules in separate locations (with long paths).

    It might be reasonable feature for E3 to assemble $EPICS_DB_INCLUDE_PATH
    at the same place (I think) it assembles $LD_LIBRARY_PATH.

    > Using other environments and/or deployment mechanisms that don't allow parallel use of multiple versions of modules, shared things get installed into a single location, so your EPICS_DB_INCLUDE_PATH stays as short as "$(TOP)/db:$(SHARED)/db".

    I sometimes begin st.cmd with a variation on the following
    to avoid a need for st.cmd to change directory.

    > epicsEnvSet("EPICS_DB_INCLUDE_PATH", "$(TOP)/db")

    or

    > epicsEnvSet("EPICS_DB_INCLUDE_PATH", "$(PWD)/../../db")

    or

    > epicsEnvSet("EPICS_DB_INCLUDE_PATH", ".:../../db")

    (I sometimes put instance specific .db files under "iocBoot/*/" )

    And I also prefer to make use of DB_INSTALLS+= in my App/db/Makefile [1]
    to copy in external db files and fragments at build time, so that the
    resulting IOC (if statically linked) is self-contained.

    (I mentions this because both $EPICS_DB_INCLUDE_PATH and DB_INSTALLS
    seem to be fairly obscure)

    [1] https://github.com/mdavidsaver/pyDevSup/blob/ea5f0d62412085dfc941e8fe758695abdfdab548/devsupApp/Db/Makefile#L17-L23

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System