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man pages section 2: System Calls

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Updated: Wednesday, July 27, 2022



mkdir, mkdirat - make a directory relative to directory file descriptor


#include <sys/stat.h>

int mkdir(const char *path, mode_t mode);
int mkdirat(int fd, const char *path, mode_t mode);


The mkdir() function creates a new directory named by the path name pointed to by path. The mode of the new directory is initialized from mode (see chmod(2) for values of mode). The access permission bits (S_IAMB) of the mode argument is modified by the process's file creation mask (see umask(2)).

The directory's owner ID is set to the process's effective user ID. The directory's group ID is set to the process's effective group ID, or if the S_ISGID bit is set in the parent directory, then the group ID of the directory is inherited from the parent. The S_ISGID bit of the new directory is inherited from the parent directory.

If path names a symbolic link, mkdir() fails and sets errno to EEXIST.

The newly created directory is empty with the exception of entries for itself (.) and its parent directory (..).

Upon successful completion, mkdir() marks for update the st_atime, st_ctime and st_mtime fields of the directory. Also, the st_ctime and st_mtime fields of the directory that contains the new entry are marked for update.

The mkdirat() function is equivalent to the mkdir() function except in the case where path specifies a relative path. In this case the newly created directory is created relative to the directory associated with the file descriptor fd instead of the current working directory. If the file descriptor was opened without O_SEARCH, the function checks whether directory searches are permitted using the current permissions of the directory underlying the file descriptor. If the file descriptor was opened with O_SEARCH, the function does not perform the check.

If mkdirat() is passed the special value AT_FDCWD in the fd parameter, the current working directory is used and the behavior is identical to a call to mkdir().

Return Values

Upon successful completion, 0 is returned. Otherwise, −1 is returned, no directory is created, and errno is set to indicate the error.


The mkdir() and mkdirat() functions will fail if:


Either a component of the path prefix denies search permission or write permission is denied on the parent directory of the directory to be created.


The directory where the new file entry is being placed cannot be extended because the user's quota of disk blocks on that file system has been exhausted; the new directory cannot be created because the user's quota of disk blocks on that file system has been exhausted; or the user's quota of inodes on the file system where the file is being created has been exhausted.


The named file already exists.


The path argument points to an illegal address.


An attempt was made to create an extended attribute that is a directory.


An I/O error has occurred while accessing the file system.


The path argument includes non-UTF8 characters and the file system accepts only file names where all characters are part of the UTF-8 character codeset.


Too many symbolic links were encountered in translating path, or a loop exists in symbolic links encountered during resolution of path


The maximum number of links to the parent directory would be exceeded.


The length of the path argument exceeds PATH_MAX, or the length of a path component exceeds NAME_MAX while _POSIX_NO_TRUNC is in effect.


A component of the path prefix does not exist or is a null pathname.


The path argument points to a remote machine and the link to that machine is no longer active.


No free space is available on the device containing the directory.


A component of the path prefix is not a directory.


The path prefix resides on a read-only file system.

The mkdirat() function will fail if:


The path argument does not specify an absolute path and the fd argument is neither AT_FDCWD nor a valid file descriptor open for reading.

The mkdir() and mkdirat() functions may fail if:


More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the path argument.


As a result of encountering a symbolic link in resolution of the path argument, the length of the substituted pathname string exceeded {PATH_MAX}.

The mkdirat() function may fail if:


The path argument is not an absolute path and fd is neither AT_FDCWD nor a file descriptor associated with a directory.


Example 1 Create a directory.

The following example demonstrates how to create a directory named /home/cnd/mod1, with read, write, and search permissions for owner and group, and with read and search permissions for others.

#include <sys/stat.h>
int status;
status = mkdir("/home/cnd/mod1",


See attributes(7) for descriptions of the following attributes:

Interface Stability

See Also

chmod(2), mknod(2), umask(2), mkdirp(3GEN), stat.h(3HEAD), attributes(7), standards(7)


The mkdir() function has been included in all Sun and Oracle releases of Solaris.

The mkdirat() function was added to Solaris in the Solaris 11.0 release.