fopen -> open()

ERRORS
       EACCES The requested access to the file is not allowed, or search permission is denied for one of  the  directories
              in  the  path  prefix of pathname, or the file did not exist yet and write access to the parent directory is
              not allowed.  (See also path_resolution(2).)

       EEXIST pathname already exists and O_CREAT and O_EXCL were used.

       EFAULT pathname points outside your accessible address space.

       EISDIR pathname refers to a directory and the access requested involved writing (that is,  O_WRONLY  or  O_RDWR  is
              set).

       ELOOP  Too many symbolic links were encountered in resolving pathname, or O_NOFOLLOW was specified but pathname was
              a symbolic link.

       EMFILE The process already has the maximum number of files open.

       ENAMETOOLONG
              pathname was too long.

       ENFILE The system limit on the total number of open files has been reached.

       ENODEV pathname refers to a device special file and no corresponding device exists.  (This is a Linux  kernel  bug;
              in this situation ENXIO must be returned.)

       ENOENT O_CREAT  is not set and the named file does not exist.  Or, a directory component in pathname does not exist
              or is a dangling symbolic link.

       ENOMEM Insufficient kernel memory was available.

       ENOSPC pathname was to be created but the device containing pathname has no room for the new file.

       ENOTDIR
              A component used as a directory in pathname is not, in fact, a directory, or O_DIRECTORY was  specified  and
              pathname was not a directory.

       ENXIO  O_NONBLOCK  |  O_WRONLY  is set, the named file is a FIFO and no process has the file open for reading.  Or,
              the file is a device special file and no corresponding device exists.

       EOVERFLOW
              pathname refers to a regular file, too large to be opened; see O_LARGEFILE above.

       EPERM  The O_NOATIME flag was specified, but the effective user ID of the caller did not match  the  owner  of  the
              file and the caller was not privileged (CAP_FOWNER).

       EROFS  pathname refers to a file on a read-only filesystem and write access was requested.

       ETXTBSY
              pathname refers to an executable image which is currently being executed and write access was requested.

       EWOULDBLOCK
              The O_NONBLOCK flag was specified, and an incompatible lease was held on the file (see fcntl(2)).