#include <sys/stat.h> int mkdir(const char *path, mode_t mode); int mkdirat(int fd, const char *path, mode_t mode);
When bits in mode other than the file permission bits are set, the meaning of these additional bits is implementation-defined.
The directory's user ID shall be set to the process' effective user ID. The directory's group ID shall be set to the group ID of the parent directory or to the effective group ID of the process. Implementations shall provide a way to initialize the directory's group ID to the group ID of the parent directory. Implementations may, but need not, provide an implementation-defined way to initialize the directory's group ID to the effective group ID of the calling process.
The newly created directory shall be an empty directory.
If path names a symbolic link, mkdir() shall fail and set errno to [EEXIST].
Upon successful completion, mkdir() shall mark for update the last data access, last data modification, and last file status change timestamps of the directory. Also, the last data modification and last file status change timestamps of the directory that contains the new entry shall be marked for update.
The mkdirat() function shall be 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 shall check 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 shall not perform the check.
In addition, the mkdirat() function shall fail if:
These functions may fail if:
The following example shows how to create a directory named /home/cnd/mod1, with read/write/search permissions for owner and group, and with read/search permissions for others.
#include <sys/types.h> #include <sys/stat.h> int status; ... status = mkdir("/home/cnd/mod1", S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
4.3 BSD detects [ENAMETOOLONG].
The POSIX.1-1990 standard required that the group ID of a newly created directory be set to the group ID of its parent directory or to the effective group ID of the creating process. FIPS 151-2 required that implementations provide a way to have the group ID be set to the group ID of the containing directory, but did not prohibit implementations also supporting a way to set the group ID to the effective group ID of the creating process. Conforming applications should not assume which group ID will be used. If it matters, an application can use chown() to set the group ID after the directory is created, or determine under what conditions the implementation will set the desired group ID.
The purpose of the mkdirat() function is to create a directory in directories other than the current working directory without exposure to race conditions. Any part of the path of a file could be changed in parallel to the call to mkdir(), resulting in unspecified behavior. By opening a file descriptor for the target directory and using the mkdirat() function it can be guaranteed that the newly created directory is located relative to the desired directory.
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