Name

Library

Synopsis

Return values

Detailed description

The flags specified are formed by or ’ing the following values

O_RDONLY        open for reading only
O_WRONLY        open for writing only
O_RDWR          open for reading and writing
O_APPEND        append on each write
O_CREAT         create file if it does not exist
O_TRUNC         truncate size to 0
O_EXCL          error if create and file exists

         

Opening a file with O_APPEND set causes each write on the file to be appended to the end. If O_TRUNC is specified and the file exists, the file is truncated to zero length. If O_EXCL is set with O_CREAT and the file already exists, wopen returns an error. This may be used to implement a simple exclusive access locking mechanism. If O_EXCL is set and the last component of the pathname is a symbolic link, wopen will fail even if the symbolic link points to a non-existent name.

If successful, wopen returns a non-negative integer, termed a file descriptor. It returns -1 on failure. The file pointer used to mark the current position within the file is set to the beginning of the file.

When a new file is created it is given the group of the directory which contains it.

The new descriptor is set to remain wopen across execve system calls; see close and fcntl.

The system imposes a limit on the number of file descriptors wopen simultaneously by one process. The getdtablesize system call returns the current system limit.

Note: 1) Mode values for group and others will be ignored for file creation, execute bit and setuid on exec bit on an file don’t have any effect while file creation.Default working directoy of a process is initalized to C: \private \UID (UID of the calling application), and any data written into this C: \private \UID directory persists between phone resets. 2) If the specified file is a symbolic link and the file it is pointing to is invalid, the symbolic link file will be automatically removed.

Limitation: A file in cannot be created with write-only permissions, hence when attempting to create a file in write-only permissions the file will be created with read-write permission. Creating a new file with O_CREAT flag, doesn’t alter the time stamp of parent directory, created entry has only two time stamps access and modification timestamps. Creation time stamp of the file is not supported, here accesstime stamp is equal to modification time stamp.

Examples

/************************************************************************
* This example creates a file in the current working directory and
* opens it in read-write mode.
************************************************************************/
#include <sys/types.h>
#include <sys/stat.h>
#include <wchar.h>
int main()
{
  int fd = 0 ;
   fd = wopen(L"Example.txt" , O_CREAT | O_EXCL , 0666) ;
   if(fd < 0 ) 
   {
      printf("Failed to create and wopen file in current working directory \n") ;
      return -1 ;
   }
   printf("File created and opened in current working directory \n"  ) ;
   return 0 ;
}

         

Output

File created and opened in current working directory

         

Errors

See also

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