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  Link RINEX files from a specified directory to the current day directory
 
  This version scans all the RINEX files in the directory and compiles a list of
  the data available from each one.   The script takes a long time to run (1 minute
  per file on a Sparc2) the first time it is executed for a RINEX directory since 
  every file is scanned, but for subsequent days, it is very quick.
  
  USAGE :    sh_link_rinex1  -year <yr>  -day <doy>  -dir <dir> 
  
          <yr> is the 4 char year of observations. [Required]
  
          <doy> is the 3 char day of the year to be linked. [Required] 
  
          <dir> the absolute or relative path to the rinex files [default ../rinex] 
  
  Example :   sh_link_rinex1 -year 1996 -day 247 -dir ../rinex/tracking
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