The mknod function makes a special file with name filename. The mode specifies the mode of the file, and may include the various special file bits, such as S_IFCHR (for a character special file) or S_IFBLK (for a block special file). See Testing File Type.

The dev argument specifies which device the special file refers to. Its exact interpretation depends on the kind of special file being created.

The return value is 0 on success and -1 on error. In addition to the usual file name errors (see File Name Errors), the following errno error conditions are defined for this function:

EPERM

The calling process is not privileged. Only the superuser can create special files.

ENOSPC

The directory or file system that would contain the new file is full and cannot be extended.

EROFS

The directory containing the new file can't be modified because it's on a read-only file system.

EEXIST

There is already a file named filename. If you want to replace this file, you must remove the old file explicitly first.