FTAB_EXT

       Routine to extract columns from a FITS (binary or ASCII) table.

       FTAB_EXT, name_or_fcb, columns, v1, [v2,..,v9, ROWS=, EXTEN_NO= ]

       name_or_fcb - either a scalar string giving the name of a FITS file
               containing a (binary or ASCII) table, or an IDL structure
               containing as file control block (FCB) returned by FITS_OPEN
               If FTAB_EXT is to be called repeatedly on the same file, then
               it is quicker to first open the file with FITS_OPEN, and then
               pass the FCB structure to FTAB_EXT
       columns - table columns to extract.  Can be either
               (1) String with names separated by commas
               (2) Scalar or vector of column numbers

       v1,...,v9 - values for the columns.   Up to 9 columns can be extracted

       ROWS -  scalar or vector giving row number(s) to extract
               Row numbers start at 0.  If not supplied or set to
               -1 then values for all rows are returned
       EXTEN_NO - Extension number to process.   If not set, then data is
               extracted from the first extension in the file (EXTEN_NO=1)

       Read wavelength and flux vectors from the first extension of a
       FITS file, 'spec.fit'.   Using FTAB_HELP,'spec.fit' we find that this
       information is in columns named 'WAVELENGTH' and 'FLUX' (in columns 1
       and 2).   To read the data
       IDL> ftab_ext,'spec.fit','wavelength,flux',w,f
               or
       IDL> ftab_ext,'spec.fit',[1,2],w,f

       FITS_READ, FITS_CLOSE, FTINFO, FTGET(), TBINFO, TBGET()

       V5.3 (uses STRSPLIT)

       version 1        W.   Landsman         August 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Improve speed processing binary tables  W. Landsman   March 2000
       Use new FTINFO calling sequence  W. Landsman   May 2000
       Don't call fits_close if fcb supplied W. Landsman May 2001
       Use STRSPLIT to parse column string  W. Landsman July 2002
       Cleanup pointers in TBINFO structure  W. Landsman November 2003

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