.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved .TH "MKNOD" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual" .\" mknod .SH PROLOG This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. .SH NAME mknod \- make a directory, a special file, or a regular file .SH SYNOPSIS .LP \fB#include .br .sp int mknod(const char *\fP\fIpath\fP\fB, mode_t\fP \fImode\fP\fB, dev_t\fP \fIdev\fP\fB); \fP \fB .br \fP .SH DESCRIPTION .LP The \fImknod\fP() function shall create a new file named by the pathname to which the argument \fIpath\fP points. .LP The file type for \fIpath\fP is OR'ed into the \fImode\fP argument, and the application shall select one of the following symbolic constants: .TS C center; l l. \fBName\fP \fBDescription\fP S_IFIFO FIFO-special S_IFCHR Character-special (non-portable) S_IFDIR Directory (non-portable) S_IFBLK Block-special (non-portable) S_IFREG Regular (non-portable) .TE .LP The only portable use of \fImknod\fP() is to create a FIFO-special file. If \fImode\fP is not S_IFIFO or \fIdev\fP is not 0, the behavior of \fImknod\fP() is unspecified. .LP The permissions for the new file are OR'ed into the \fImode\fP argument, and may be selected from any combination of the following symbolic constants: .TS C center; l2 l. \fBName\fP \fBDescription\fP 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. .TE .LP 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 \fImode\fP shall be modified by the file mode creation mask of the process. The \fImknod\fP() function shall clear each bit whose corresponding bit in the file mode creation mask of the process is set. .LP If \fIpath\fP names a symbolic link, \fImknod\fP() shall fail and set \fIerrno\fP to [EEXIST]. .LP Upon successful completion, \fImknod\fP() shall mark for update the \fIst_atime\fP, \fIst_ctime\fP, and \fIst_mtime\fP fields of the file. Also, the \fIst_ctime\fP and \fIst_mtime\fP fields of the directory that contains the new entry shall be marked for update. .LP Only a process with appropriate privileges may invoke \fImknod\fP() for file types other than FIFO-special. .SH RETURN VALUE .LP Upon successful completion, \fImknod\fP() shall return 0. Otherwise, it shall return -1, the new file shall not be created, and \fIerrno\fP shall be set to indicate the error. .SH ERRORS .LP The \fImknod\fP() function shall fail if: .TP 7 .B EACCES A component of the path prefix denies search permission, or write permission is denied on the parent directory. .TP 7 .B EEXIST The named file exists. .TP 7 .B EINVAL An invalid argument exists. .TP 7 .B EIO An I/O error occurred while accessing the file system. .TP 7 .B ELOOP A loop exists in symbolic links encountered during resolution of the \fIpath\fP argument. .TP 7 .B ENAMETOOLONG The length of a pathname exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}. .TP 7 .B ENOENT A component of the path prefix specified by \fIpath\fP does not name an existing directory or \fIpath\fP is an empty string. .TP 7 .B ENOSPC The directory that would contain the new file cannot be extended or the file system is out of file allocation resources. .TP 7 .B ENOTDIR A component of the path prefix is not a directory. .TP 7 .B EPERM The invoking process does not have appropriate privileges and the file type is not FIFO-special. .TP 7 .B EROFS The directory in which the file is to be created is located on a read-only file system. .sp .LP The \fImknod\fP() function may fail if: .TP 7 .B ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the \fIpath\fP argument. .TP 7 .B ENAMETOOLONG Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}. .sp .LP \fIThe following sections are informative.\fP .SH EXAMPLES .SS Creating a FIFO Special File .LP The following example shows how to create a FIFO special file named \fB/home/cnd/mod_done\fP, with read/write permissions for owner, and with read permissions for group and others. .sp .RS .nf \fB#include #include .sp dev_t dev; int status; \&... status = mknod("/home/cnd/mod_done", S_IFIFO | S_IWUSR | S_IRUSR | S_IRGRP | S_IROTH, dev); \fP .fi .RE .SH APPLICATION USAGE .LP The \fImkfifo\fP() function is preferred over this function for making FIFO special files. .SH RATIONALE .LP 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 \fIchown\fP() to set the group ID after the file is created, or determine under what conditions the implementation will set the desired group ID. .SH FUTURE DIRECTIONS .LP None. .SH SEE ALSO .LP \fIchmod\fP(), \fIcreat\fP(), \fIexec\fP(), \fImkdir\fP(), \fImkfifo\fP() , \fIopen\fP(), \fIstat\fP(), \fIumask\fP(), the Base Definitions volume of IEEE\ Std\ 1003.1-2001, \fI\fP .SH COPYRIGHT Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .