### 14.9 Creating Directories ¶

Directories are created with the `mkdir` function. (There is also a shell command `mkdir` which does the same thing.)

Function: `int` mkdir `(const char *filename, mode_t mode)` ¶

  Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.

  The `mkdir` function creates a new, empty directory with name filename.

  The argument mode specifies the file permissions for the new directory file. See The Mode Bits for Access Permission, for more information about this.

  A return value of `0` indicates successful completion, and `-1` indicates failure. In addition to the usual file name syntax errors (see File Name Errors), the following `errno` error conditions are defined for this function:

  `EACCES`

    Write permission is denied for the parent directory in which the new directory is to be added.

  `EEXIST`

    A file named filename already exists.

  `EMLINK`

    The parent directory has too many links (entries).

    Well-designed file systems never report this error, because they permit more links than your disk could possibly hold. However, you must still take account of the possibility of this error, as it could result from network access to a file system on another machine.

  `ENOSPC`

    The file system doesn’t have enough room to create the new directory.

  `EROFS`

    The parent directory of the directory being created is on a read-only file system and cannot be modified.

  To use this function, your program should include the header file `sys/stat.h`.

Function: `int` mkdirat `(int filedes, const char *filename, mode_t mode)` ¶

  | MT-Safe | AS-Unsafe corrupt | AC-Unsafe corrupt | See POSIX Safety Concepts.

  This function is a descriptor-relative version of the `mkdir` function above. See Descriptor-Relative Access.

  Compared to `mkdir`, some additional error conditions can occur. See Descriptor-Relative Access.