C_F_STRPOINTER

Intel® Fortran Compiler Classic and Intel® Fortran Compiler Developer Guide and Reference

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ID 767251

Date 3/22/2024

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C_F_STRPOINTER

Intrinsic Module Subroutine (Generic): Associates a Fortran character data pointer with a C string.

Module

USE, INTRINSIC :: ISO_C_BINDING

Syntax

CALL C_F_STRPOINTER(cstrarray, fstrptr [, nchars])

-or-

CALL C_F_STRPOINTER(cstrptr, fstrptr [, nchars])

cstrarray	(Input) Is a scalar rank 1 character array of type C_CHAR, with a length type parameter of one. The actual argument must have the TARGET attribute and be simply contiguous; it must be of derived type C_PTR.
cstrptr	(Input) Is a scalar with type C_PTR. It has the value of the C address of a contiguous array STRING containing `nchars` characters. It must not have a value that is the C address of a Fortran variable that does not have the TARGET attribute.
fstrptr	(Output) Is a deferred-length character pointer whose kind type is C_CHAR. If `cstrarray` appears, `fstrptr` becomes pointer-associated with the leftmost characters of the actual argument. If `cstrptr` appears, `fstrptr` becomes pointer-associated with the leftmost characters, in array element order, of STRING. The length type parameter of `fstrptr` becomes the largest value for which no C null characters appear in the sequence, and is less than or equal to `nchars` if it is present; otherwise, it is the size of `cstrarray`.
nchars	(Optional, input) Must be of type integer with a nonnegative value. It must be present if `cstrarray` is assumed-size, or if `cstrptr` appears. If `cstrarray` appears, `nchars` must not have a value greater than the size of `cstrarray`.

Examples

The following procedure prints the value of up to the first 2048 characters of the PATH environment variable returned by calling the C library function getenv:

   SUBROUTINE print_path () BIND (C) 
      USE ISO_C_BINDING
      TYPE (C_PTR) :: getenv_res
     CHARACTER(LEN=:,KIND=C_CHAR),POINTER :: path
      INTERFACE
        FUNCTION getenv (env_var) BIND (C)
          IMPORT C_PTR, C_CHAR
          TYPE (C_PTR) :: getenv
          CHARACTER(KIND=C_CHAR),INTENT(IN) :: env_var (*)
        END FUNCITON
      END INTERFACE
      getenv_res = getenv (“PATH”//C_NULL_CHAR)
      IF (.NOT. C_ASSOCIATED (getenv_res)) THEN
        PRINT *, “PATH not set”
      ELSE
        CALL C_F_STRPOINTER (getenv_res, path, 2048)
        PRINT *, TRIM (path)
      END IF 
    END SUBROUTINE print_path

The following procedure writes a C string to a Fortran internal file. The string can be of any length. The nchars argument in the call to C_F_POINTER limits the length of f_char_ptr to no more than n_chars characters, which is the maximum length of the internal file:

    SUBROUTINE write_string (c_string, i_file) BIND (C) 
      USE ISO_C_BINDING
      CHARACTER(LEN=:),INTENT(OUT) :: i_file
      CHARACTER(LEN=:,KIND=C_CHAR),TARGET,INTENT(IN) :: c_string
      CHARACTER(LEN=:,KIND=C_CHAR),POINTER :: f_char_ptr
      INTEGER :: n_chars
      n_chars = LEN(i_file)
      CALL C_F_STRPOINTER (c_string, f_char_ptr, n_chars)
      PRINT i_file, f_char_ptr
    END SUBROUTINE write_string

Parent topic: C to D

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Intel® Fortran Compiler Classic and Intel® Fortran Compiler Developer Guide and Reference

C_F_STRPOINTER

Module

Syntax

Examples

See Also