.\" This manpage is Copyright (C) 1992 Drew Eckhardt; .\" and Copyright (C) 1993 Michael Haardt .\" and Copyright (C) 1993,1994 Ian Jackson .\" and Copyright (C) 2006, 2014, Michael Kerrisk .\" .\" SPDX-License-Identifier: GPL-1.0-or-later .\" .\" Modified 1996-08-18 by urs .\" Modified 2003-04-23 by Michael Kerrisk .\" Modified 2004-06-23 by Michael Kerrisk .\" .TH mknod 2 2023-03-31 "Linux man-pages 6.04" .SH NAME mknod, mknodat \- create a special or ordinary file .SH LIBRARY Standard C library .RI ( libc ", " \-lc ) .SH SYNOPSIS .nf .B #include .PP .BI "int mknod(const char *" pathname ", mode_t " mode ", dev_t " dev ); .PP .BR "#include " "/* Definition of AT_* constants */" .B #include .PP .BI "int mknodat(int " dirfd ", const char *" pathname ", mode_t " mode \ ", dev_t " dev ); .fi .PP .RS -4 Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .RE .PP .BR mknod (): .nf _XOPEN_SOURCE >= 500 .\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE .fi .SH DESCRIPTION The system call .BR mknod () creates a filesystem node (file, device special file, or named pipe) named .IR pathname , with attributes specified by .I mode and .IR dev . .PP The .I mode argument specifies both the file mode to use and the type of node to be created. It should be a combination (using bitwise OR) of one of the file types listed below and zero or more of the file mode bits listed in .BR inode (7). .PP The file mode is modified by the process's .I umask in the usual way: in the absence of a default ACL, the permissions of the created node are .RI ( mode " & \[ti]" umask ). .PP The file type must be one of .BR S_IFREG , .BR S_IFCHR , .BR S_IFBLK , .BR S_IFIFO , or .B S_IFSOCK .\" (S_IFSOCK since Linux 1.2.4) to specify a regular file (which will be created empty), character special file, block special file, FIFO (named pipe), or UNIX domain socket, respectively. (Zero file type is equivalent to type .BR S_IFREG .) .PP If the file type is .B S_IFCHR or .BR S_IFBLK , then .I dev specifies the major and minor numbers of the newly created device special file .RB ( makedev (3) may be useful to build the value for .IR dev ); otherwise it is ignored. .PP If .I pathname already exists, or is a symbolic link, this call fails with an .B EEXIST error. .PP The newly created node will be owned by the effective user ID of the process. If the directory containing the node has the set-group-ID bit set, or if the filesystem is mounted with BSD group semantics, the new node will inherit the group ownership from its parent directory; otherwise it will be owned by the effective group ID of the process. .\" .\" .SS mknodat() The .BR mknodat () system call operates in exactly the same way as .BR mknod (), except for the differences described here. .PP If the pathname given in .I pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor .I dirfd (rather than relative to the current working directory of the calling process, as is done by .BR mknod () for a relative pathname). .PP If .I pathname is relative and .I dirfd is the special value .BR AT_FDCWD , then .I pathname is interpreted relative to the current working directory of the calling process (like .BR mknod ()). .PP If .I pathname is absolute, then .I dirfd is ignored. .PP See .BR openat (2) for an explanation of the need for .BR mknodat (). .SH RETURN VALUE .BR mknod () and .BR mknodat () return zero on success. On error, \-1 is returned and .I errno is set to indicate the error. .SH ERRORS .TP .B EACCES The parent directory does not allow write permission to the process, or one of the directories in the path prefix of .I pathname did not allow search permission. (See also .BR path_resolution (7).) .TP .B EBADF .RB ( mknodat ()) .I pathname is relative but .I dirfd is neither .B AT_FDCWD nor a valid file descriptor. .TP .B EDQUOT The user's quota of disk blocks or inodes on the filesystem has been exhausted. .TP .B EEXIST .I pathname already exists. This includes the case where .I pathname is a symbolic link, dangling or not. .TP .B EFAULT .IR pathname " points outside your accessible address space." .TP .B EINVAL .I mode requested creation of something other than a regular file, device special file, FIFO or socket. .TP .B ELOOP Too many symbolic links were encountered in resolving .IR pathname . .TP .B ENAMETOOLONG .IR pathname " was too long." .TP .B ENOENT A directory component in .I pathname does not exist or is a dangling symbolic link. .TP .B ENOMEM Insufficient kernel memory was available. .TP .B ENOSPC The device containing .I pathname has no room for the new node. .TP .B ENOTDIR A component used as a directory in .I pathname is not, in fact, a directory. .TP .B ENOTDIR .RB ( mknodat ()) .I pathname is relative and .I dirfd is a file descriptor referring to a file other than a directory. .TP .B EPERM .I mode requested creation of something other than a regular file, FIFO (named pipe), or UNIX domain socket, and the caller is not privileged (Linux: does not have the .B CAP_MKNOD capability); .\" For UNIX domain sockets and regular files, EPERM is returned only in .\" Linux 2.2 and earlier; in Linux 2.4 and later, unprivileged can .\" use mknod() to make these files. also returned if the filesystem containing .I pathname does not support the type of node requested. .TP .B EROFS .I pathname refers to a file on a read-only filesystem. .SH VERSIONS POSIX.1-2001 says: "The only portable use of .BR mknod () is to create a FIFO-special file. If .I mode is not .B S_IFIFO or .I dev is not 0, the behavior of .BR mknod () is unspecified." However, nowadays one should never use .BR mknod () for this purpose; one should use .BR mkfifo (3), a function especially defined for this purpose. .PP Under Linux, .BR mknod () cannot be used to create directories. One should make directories with .BR mkdir (2). .\" and one should make UNIX domain sockets with socket(2) and bind(2). .SH STANDARDS POSIX.1-2008. .SH HISTORY .TP .BR mknod () SVr4, 4.4BSD, POSIX.1-2001 (but see VERSIONS). .\" The Linux version differs from the SVr4 version in that it .\" does not require root permission to create pipes, also in that no .\" EMULTIHOP, ENOLINK, or EINTR error is documented. .TP .BR mknodat () Linux 2.6.16, glibc 2.4. POSIX.1-2008. .SH NOTES There are many infelicities in the protocol underlying NFS. Some of these affect .BR mknod () and .BR mknodat (). .SH SEE ALSO .BR mknod (1), .BR chmod (2), .BR chown (2), .BR fcntl (2), .BR mkdir (2), .BR mount (2), .BR socket (2), .BR stat (2), .BR umask (2), .BR unlink (2), .BR makedev (3), .BR mkfifo (3), .BR acl (5), .BR path_resolution (7)