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Manual Reference Pages  - system_opendir (3)

NAME
system_opendir(3f) - [M_system:QUERY_FILE] open directory stream by calling opendir(3c) (LICENSE:PD)

CONTENTS

Synopsis
Description
Return Value
Errors
Application Usage
Options
Returns
Example
Author
License

SYNOPSIS
subroutine system_opendir(dirname,dir,ierr) 

   character(len=*), intent(in) :: dirname
   type(c_ptr)                  :: dir
   integer,intent(out)          :: ierr

DESCRIPTION
The system_opendir(3f) procedure opens a directory stream corresponding to the directory named by the dirname argument. The directory stream is positioned at the first entry.

RETURN VALUE
Upon successful completion, a pointer to a C dir type is returned. Otherwise, these functions shall return a null pointer and set IERR to indicate the error.

ERRORS

An error corresponds to a condition described in opendir(3c):
EACCES Search permission is denied for the component of the path prefix of dirname or read permission is denied for dirname.
ELOOP A loop exists in symbolic links encountered during resolution of the dirname argument.
ENAMETOOLONG
  The length of a component of a pathname is longer than {NAME_MAX}.
ENOENT A component of dirname does not name an existing directory or dirname is an empty string.
ENOTDIR
  A component of dirname names an existing file that is neither a directory nor a symbolic link to a directory.
ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the dirname argument.
EMFILE All file descriptors available to the process are currently open.
ENAMETOOLONG
  The length of a pathname exceeds {PATH_MAX}, or pathname resolution of a symbolic link produced an intermediate result with a length that exceeds {PATH_MAX}.
ENFILE Too many files are currently open in the system.

APPLICATION USAGE
The opendir() function should be used in conjunction with readdir(), closedir(), and rewinddir() to examine the contents of the directory (see the EXAMPLES section in readdir()). This method is recommended for portability.

OPTIONS
dirname name of directory to open a directory stream for

RETURNS
dir pointer to directory stream. If an error occurred, it will not be associated.
ierr 0 indicates no error occurred

EXAMPLE
Sample program: 

   program demo_system_opendir
   use M_system, only : system_opendir,system_readdir
   use M_system, only : system_closedir
   use iso_c_binding
   implicit none
   type(c_ptr)                  :: dir
   character(len=:),allocatable :: filename
   integer                      :: ierr
   !--- open directory stream to read from
   call system_opendir(’.’,dir,ierr)
   if(ierr.eq.0)then
      !--- read directory stream
      do
         call system_readdir(dir,filename,ierr)
         if(filename.eq.’ ’)exit
         write(*,*)filename
      enddo
   endif
   !--- close directory stream
   call system_closedir(dir,ierr)
   end program demo_system_opendir

AUTHOR
John S. Urban

LICENSE
Public Domain

system_opendir (3) March 11, 2021
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