write Function

The write function is used to write data to a file (identified by a handle), without formatting, type conversion, or buffering.

Handle

Selector (file descriptor) of an open file.

Buffer

The address where the data write is to be stored.

Length

The number of bytes to be write.

int

Number of bytes written.

errno

Iff the write fails, the global variable errno is set to one of:

EBADF

Handle not open

#include <stdio.h>
#include <io.h> 
#include <fcntl.h>
#include <errno.h>

int main () {
  int Account_Master;
  char Buffer [100]; 
  int Maximum; 
  int Actual;
  int More;
  /* Other declarations */
  Maximum = 100;
  Account_Master = open ("accounts.dat", O_WRONLY);
  if (Account_Master >0) {
    printf ("Open succeeded.\n");
  } else {
    printf ("Open failed.\n")
    switch (errno) {
      case EACCES:  printf ("Permission denied.\n"); break;
      case EINVACC: printf ("Invalid access mode.\n"); break;
      case EMFILE:  printf ("No file handle available.\n"); break;
      case ENOENT:  printf ("File or path not found.\n"); break;
      default:      printf ("Unknown error.\n"); break;
    }
  /* File processing */
  More = 1;
  while (More == 1)
    /* Record preparation */
    Actual = write (Account_Master, Buffer, Maximum); 
    if (Actual < Maximum) { 
      printf ("An incomplete record was written.\n")
    }
  }
  
  if (close (Account_Master) == 0) {
    printf ("Close succeeded.\n");
  } else {
    printf ("Close failed.\n")
    switch (errno) {
      case EBADF:  printf ("File not open.\n"); break;
      default:     printf ("Unknown error.\n"); break;
    }
  }
  return 0;
}