Name

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  FXPOPENR

Author

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  Craig B. Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770
  craigm@lheamail.gsfc.nasa.gov
  UPDATED VERSIONs can be found on my WEB PAGE:
      http://cow.physics.wisc.edu/~craigm/idl/idl.html

Purpose

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  Internal routine to open a Unix pipe command for read access.

Description

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  See the following procedures for appropriate documentation.
    FXGOPEN - open resource
    FXGCLOSE - close resource
    FXGREAD - read from resource
    FXGWRITE - write to resource
    FXGSEEK - seek on resource (i.e., perform POINT_LUN)
    FXGFILTERED - determine if resource is a normal file.
  Usage: FXPOPENR, UNIT, COMMAND, ERRMSG=ERRMSG

Parameters

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  unit - FXPOPENR returns the pipe LUN, created by GET_LUN in this
          parameter. The LUN should not be "pre-opened".
          Unformatted reads on this LUN should be performed with
          FXPREAD.
  command - a scalar string, the pipe command to execute. The
            standard output of the command is redirected into UNIT.
            Standard error is not redirected.
            A failure of the command can only be discovered upon
            trying to read from the LUN with FXPREAD.

Keywords

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  errmsg - If set to defined value upon input, an error message is
            returned upon output. If no error occurs then ERRMSG is
            not changed. If an error occurs and ERRMSG is not
            defined, then FXPOPENR issues a MESSAGE.

Side Effects

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  The pipe command is opened with SPAWN, and an additional cache file
  is opened with read/write access.
  The FXFILTER family of commons is updated.

Modification History

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  Changed copyright notice, 21 Sep 2000, CM
  Added the OPEN,/DELETE keyword, so that tmp-files are
    automatically deleted when closed, 18 Feb 2006, CM
  Added quotation marks to the list of characters which are
    protected, while making a tmpfile name, 22 Oct 2006, CM
  2012-04-17 Promote file position pointers to LONG64, CM