int open(const char *path,int flags,... /*mode_t mode*/);

use

open open a file descriptor to the specified pathname.
The flags argument allow to open for specific operation and set flags on the file decsriptor.

avalibles flags

  • O_READONLY
    open in readonly
  • O_WRITEONLY
  • O_CREAT
    create the file is it don’t exist the optional argument mode is used with this flags
  • O_EXCL
    when used with O_CREAT , make sure a file is created trigger an error if it can’t
  • O_CLOEXEC
    close the file descriptor when the execve syscall is call
  • O_APPEND
    set the file desciptor in append mode , before each write , the kernel seek to the end of the file
  • O_DIRECTORY
    open a directory
    if you want to open a directory you might want to use opendir instead of the raw syscall

    return code

    open return the id the the new file descriptor or -1 and set errno if an error happend

  • EFAULT
    path point to outside of the addrassable space
  • EEXIST
    O_CREAT and O_EXCL were set but the file aready exist
  • ENOENT
    path don’t exist
  • EISDIR
    path is a directory but O_DIRECTORY was noe specified
  • ENOTDIR
    O_DIRECTORY was specified but path is not a directory
  • EPERM
    permission issue