--- name: "mkdirat" section: "2" platform: "linux" package: "man-pages" version: "6.19-1" release: "Arch Linux 2026-11-01" platforms: ["linux", "freebsd", "macos"] url: "https://new.carta.tech/mkdir/2" --- # mkdirat(2) create a directory Part of [mkdir(2)](/mkdir/2.md). ## NAME mkdir, mkdirat - create a directory ## LIBRARY Standard C library (*libc*, *-lc*) ## SYNOPSIS ``` #include ``` **int mkdir(const char \****path***, mode\_t** *mode***);** **#include \** /\* Definition of AT\_\* constants \*/ **#include \** **int mkdirat(int** *dirfd***, const char \****path***, mode\_t** *mode***);** Feature Test Macro Requirements for glibc (see [**feature\_test\_macros**(7)](/feature_test_macros/7.md)): **mkdirat**(): ``` Since glibc 2.10: _POSIX_C_SOURCE >= 200809L Before glibc 2.10: _ATFILE_SOURCE ``` ## DESCRIPTION **mkdir**() attempts to create a directory named *path*. The argument *mode* specifies the mode for the new directory (see [**inode**(7)](/inode/7.md)). It is modified by the process's *umask* in the usual way: in the absence of a default ACL, the mode of the created directory is (*mode* & ~*umask* & 0777). Whether other *mode* bits are honored for the created directory depends on the operating system. For Linux, see VERSIONS below. The newly created directory will be owned by the effective user ID of the process. If the directory containing the file has the set-group-ID bit set, or if the filesystem is mounted with BSD group semantics (*mount -o bsdgroups* or, synonymously *mount -o grpid*), the new directory will inherit the group ownership from its parent; otherwise it will be owned by the effective group ID of the process. If the parent directory has the set-group-ID bit set, then so will the newly created directory. ### mkdirat() The **mkdirat**() system call operates in exactly the same way as **mkdir**(), except for the differences described here. If *path* is relative, then it is interpreted relative to the directory referred to by the file descriptor *dirfd* (rather than relative to the current working directory of the calling process, as is done by **mkdir**() for a relative pathname). If *path* is relative and *dirfd* is the special value **AT\_FDCWD**, then *path* is interpreted relative to the current working directory of the calling process (like **mkdir**()). If *path* is absolute, then *dirfd* is ignored. See [**openat**(2)](/openat/2.md) for an explanation of the need for **mkdirat**(). ## RETURN VALUE **mkdir**() and **mkdirat**() return zero on success. On error, -1 is returned and *errno* is set to indicate the error. ## ERRORS - **EACCES** The parent directory does not allow write permission to the process, or one of the directories in *path* did not allow search permission. (See also [**path\_resolution**(7)](/path_resolution/7.md).) - **EBADF** (**mkdirat**()) *path* is relative but *dirfd* is neither **AT\_FDCWD** nor a valid file descriptor. - **EDQUOT** The user's quota of disk blocks or inodes on the filesystem has been exhausted. - **EEXIST** *path* already exists (not necessarily as a directory). This includes the case where *path* is a symbolic link, dangling or not. - **EFAULT** *path* points outside your accessible address space. - **EINVAL** The final component ("basename") of the new directory's *path* is invalid (e.g., it contains characters not permitted by the underlying filesystem). - **ELOOP** Too many symbolic links were encountered in resolving *path*. - **EMLINK** The number of links to the parent directory would exceed **LINK\_MAX**. - **ENAMETOOLONG** *path* was too long. - **ENOENT** A directory component in *path* does not exist or is a dangling symbolic link. - **ENOMEM** Insufficient kernel memory was available. - **ENOSPC** The device containing *path* has no room for the new directory. - **ENOSPC** The new directory cannot be created because the user's disk quota is exhausted. - **ENOTDIR** A component used as a directory in *path* is not, in fact, a directory. - **ENOTDIR** (**mkdirat**()) *path* is relative and *dirfd* is a file descriptor referring to a file other than a directory. - **EPERM** The filesystem containing *path* does not support the creation of directories. - **EROFS** *path* refers to a file on a read-only filesystem. - **EOVERFLOW** UID or GID mappings (see [**user\_namespaces**(7)](/user_namespaces/7.md)) have not been configured. ## VERSIONS Under Linux, apart from the permission bits, the **S\_ISVTX** *mode* bit is also honored. ### glibc notes On older kernels where **mkdirat**() is unavailable, the glibc wrapper function falls back to the use of **mkdir**(). When *path* is relative, glibc constructs a pathname based on the symbolic link in */proc/self/fd* that corresponds to the *dirfd* argument. ## STANDARDS POSIX.1-2024. ## HISTORY - **mkdir**() 4\.2BSD, SVr4, POSIX.1-1988. - **mkdirat**() glibc 2.4, Linux 2.6.16, POSIX.1-2008. ## NOTES There are many infelicities in the protocol underlying NFS. Some of these affect **mkdir**(). ## SEE ALSO [**mkdir**(1)](/mkdir/1.md), [**chmod**(2)](/chmod/2.md), [**chown**(2)](/chown/2.md), [**mknod**(2)](/mknod/2.md), [**mount**(2)](/mount/2.md), [**rmdir**(2)](/rmdir/2.md), [**stat**(2)](/stat/2.md), [**umask**(2)](/umask/2.md), [**unlink**(2)](/unlink/2.md), [**acl**(5)](/acl/5.md), [**path\_resolution**(7)](/path_resolution/7.md)