int mknod(const char *path, mode_t mode, dev_t
The mknod() function shall create a new file named by the pathname to which the argument path points.
The file type for path is OR'ed into the mode argument, and the application shall select one of the following symbolic constants:
The only portable use of mknod() is to create a FIFO-special file. If mode is not S_IFIFO or dev is not 0, the behavior of mknod() is unspecified.
The permissions for the new file are OR'ed into the mode argument, and may be selected from any combination of the following symbolic constants:
|S_ISUID||Set user ID on execution.|
|S_ISGID||Set group ID on execution.|
|S_IRWXU||Read, write, or execute (search) by owner.|
|S_IRUSR||Read by owner.|
|S_IWUSR||Write by owner.|
|S_IXUSR||Execute (search) by owner.|
|S_IRWXG||Read, write, or execute (search) by group.|
|S_IRGRP||Read by group.|
|S_IWGRP||Write by group.|
|S_IXGRP||Execute (search) by group.|
|S_IRWXO||Read, write, or execute (search) by others.|
|S_IROTH||Read by others.|
|S_IWOTH||Write by others.|
|S_IXOTH||Execute (search) by others.|
|S_ISVTX||On directories, restricted deletion flag.|
The user ID of the file shall be initialized to the effective user ID of the process. The group ID of the file shall be initialized to either the effective group ID of the process or the group ID of the parent directory. Implementations shall provide a way to initialize the file's group ID to the group ID of the parent directory. Implementations may, but need not, provide an implementation-defined way to initialize the file's group ID to the effective group ID of the calling process. The owner, group, and other permission bits of mode shall be modified by the file mode creation mask of the process. The mknod() function shall clear each bit whose corresponding bit in the file mode creation mask of the process is set.
If path names a symbolic link, mknod() shall fail and set errno to [EEXIST].
Upon successful completion, mknod() shall mark for update the st_atime, st_ctime, and st_mtime fields of the file. Also, the st_ctime and st_mtime fields of the directory that contains the new entry shall be marked for update.
Only a process with appropriate privileges may invoke mknod() for file types other than FIFO-special.
Upon successful completion, mknod() shall return 0. Otherwise, it shall return -1, the new file shall not be created, and errno shall be set to indicate the error.
The mknod() function shall fail if:
The mknod() function may fail if:
The following sections are informative.
The following example shows how to create a FIFO special file named /home/cnd/mod_done, with read/write permissions for owner, and with read permissions for group and others.
#include <sys/types.h> #include <sys/stat.h> dev_t dev; int status; ... status = mknod("/home/cnd/mod_done", S_IFIFO | S_IWUSR | S_IRUSR | S_IRGRP | S_IROTH, dev);
The mkfifo() function is preferred over this function for making FIFO special files.
The POSIX.1-1990 standard required that the group ID of a newly created file 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 file is created, or determine under what conditions the implementation will set the desired group ID.
chmod() , creat() , exec() , mkdir() , mkfifo() , open() , stat() , umask() , the Base Definitions volume of IEEE Std 1003.1-2001, <sys/stat.h>