Procedure

     ISOPEN ( Is a file currently open? )

     LOGICAL FUNCTION ISOPEN ( FILE )

Abstract

     Determine whether a named file is currently open.

Required_Reading

     None.

Keywords

     FILES

Declarations

     IMPLICIT NONE

     CHARACTER*(*)    FILE

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     FILE       I   Name of the file in question.

     The function returns the value .TRUE. if the file is open, .FALSE.
     otherwise.

Detailed_Input

     FILE     is the name of the file in question.

Detailed_Output

     The function returns the value .TRUE. if the file is open, .FALSE.
     otherwise.

Parameters

     None.

Exceptions

     1)  If the filename is blank, the error SPICE(BLANKFILENAME) is
         signaled.

     2)  If an error occurs during the execution of the Fortran INQUIRE
         statement, the error SPICE(INQUIREFAILED) is signaled.

Files

     None.

Particulars

     Use the Fortran INQUIRE statement to determine the open status
     of FILE.

Examples

     The following code fragment illustrates the use of ISOPEN.

           IF ( .NOT. ISOPEN ( FILE ) ) THEN
              Open the file here
           ELSE
              ERROR = 'Input file is already open.'
           END IF

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

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

Version

    SPICELIB Version 1.2.0, 12-AUG-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.1.0, 29-FEB-1996 (KRG)

        Added a local logical variable that is used as temporary
        storage for the results from the INQUIRE statement rather
        than using the function name. This solved a problem on the
        macintosh.

    SPICELIB Version 1.0.0, 05-OCT-1994 (KRG)