Name

---

      GET_PIPE_FILESIZE

Purpose

---

      Determine the number of bytes in a unit opened as a pipe with SPAWN

Explanation

---

      Reads into a buffer until the end of file is reached and then counts the
      number of bytes read. Needed because the fstat.size field is not
      automatically set for a unit opened as a pipe.

Calling Sequence

---

      GET_PIPE_FILESIZE,unit, nbytes_in_file, BUFFER =

Inputs

---

      unit - IDL unit number of a previously opened file. For example,
        an FPACK ( http://heasarc.gsfc.nasa.gov/fitsio/fpack/ ) compressed
        FITS file could be opened as follows:
        IDL> spawn,'funpack -S test.fits.fz', unit=unit

Outputs

---

      nbytes_in_file - Unsigned long64 integer giving number of bytes in
        the file.

Input Keyword Parameters

---

      BUFFER Integer giving number of bytes in the buffer. Default =
    . 1000000

Notes

---

      Unite must be opened prior to calling GET_PIPE_FILESIZE, and the number
      of bytes is counted from the current pointer position. The pointer is
      left at the end of the file upon return.

Procedures Used

---

    SETDEFAULTVALUE

Revision History

---

      Written, W. Landsman Adnet Dec 2010
On_error,2
compile_opt idl2
nbytes = 0ULL
setdefaultvalue, buffer, 1000000
ON_IOerror,Done
b= bytarr(buffer,/noz)
while 1 do begin
  readu,unit,b
  nbytes += buffer
endwhile
one:
On_IOError, null
nbytes += (fstat(unit)).transfer_count

Return

---

end