Procedure

     READLN ( Read a text line from a logical unit )

     SUBROUTINE READLN ( UNIT, LINE, EOF )

Abstract

     Read a single line of text from the Fortran logical unit UNIT,
     reporting the end of file if it occurs.

Required_Reading

     None.

Keywords

     ASCII
     FILES
     TEXT

Declarations

     INTEGER            UNIT
     CHARACTER*(*)      LINE
     LOGICAL            EOF

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     UNIT       I   The Fortran unit number to use for input.
     LINE       O   The line read from the file.
     EOF        O   A logical flag indicating the end of file.

Detailed_Input

     UNIT     is the Fortran unit number for the input. This may
              be either the unit number for the terminal, or the
              unit number of a previously opened text file.

Detailed_Output

     LINE     is the next text line encountered when reading from UNIT.

              If the length of the character string LINE is shorter
              than the length of the current line in the text file, the
              line is truncated on the right by the Fortran READ
              statement, filling LINE with the first LEN(LINE)
              characters from the current line in the file.

              If an error or the end of file occurs during the
              attempt to read from UNIT, the value of this variable
              is not guaranteed.

     EOF      is .TRUE. if the end of file ( IOSTAT < 0 ) is
              encountered during the attempt to read from unit UNIT.
              Otherwise, this variable will be set to .FALSE.

Parameters

     None.

Exceptions

     This routine only checks in with the error handler in the event
     that an error occurred. (Discovery check in)

     1)  If an error occurs while attempting to read from the text file
         attached to UNIT, the error SPICE(FILEREADFAILED) is signaled.

Files

     None.

Particulars

     This routine will read a single line, a text record, from the
     logical unit UNIT. UNIT may be the terminal, or it may be a
     logical unit number obtained from a Fortran OPEN or INQUIRE
     statement. This routine will set a logical flag, EOF, on output
     if the end of the file is encountered during the read attempt.

Examples

     CALL READLN ( UNIT, LINE, EOF )

     IF ( EOF ) THEN
        < The end of file, deal with it appropriately >
     END IF

     You now have a line of text from unit UNIT.

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

     J. Diaz del Rio    (ODC Space)
     K.R. Gehringer     (JPL)

Version

    SPICELIB Version 1.1.0, 12-AUG-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard. Removed
        unnecessary $Version history entries for Beta versions.

    SPICELIB Version 1.0.0, 20-DEC-1995 (KRG)