mirror of https://github.com/mkerrisk/man-pages
208 lines
6.6 KiB
Plaintext
208 lines
6.6 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "MKNOD" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" mknod
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.SH NAME
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mknod \- make a directory, a special file, or a regular file
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.SH SYNOPSIS
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.LP
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\fB#include <sys/stat.h>
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.br
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.sp
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int mknod(const char *\fP\fIpath\fP\fB, mode_t\fP \fImode\fP\fB, dev_t\fP
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\fIdev\fP\fB); \fP
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\fB
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fImknod\fP() function shall create a new file named by the pathname
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to which the argument \fIpath\fP points.
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.LP
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The file type for \fIpath\fP is OR'ed into the \fImode\fP argument,
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and the application shall select one of the following
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symbolic constants:
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.TS C
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center; l l.
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\fBName\fP \fBDescription\fP
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S_IFIFO FIFO-special
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S_IFCHR Character-special (non-portable)
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S_IFDIR Directory (non-portable)
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S_IFBLK Block-special (non-portable)
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S_IFREG Regular (non-portable)
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.TE
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.LP
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The only portable use of \fImknod\fP() is to create a FIFO-special
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file. If \fImode\fP is not S_IFIFO or \fIdev\fP is not 0,
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the behavior of \fImknod\fP() is unspecified.
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.LP
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The permissions for the new file are OR'ed into the \fImode\fP argument,
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and may be selected from any combination of the
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following symbolic constants:
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.TS C
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center; l2 l.
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\fBName\fP \fBDescription\fP
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S_ISUID Set user ID on execution.
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S_ISGID Set group ID on execution.
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S_IRWXU Read, write, or execute (search) by owner.
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S_IRUSR Read by owner.
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S_IWUSR Write by owner.
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S_IXUSR Execute (search) by owner.
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S_IRWXG Read, write, or execute (search) by group.
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S_IRGRP Read by group.
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S_IWGRP Write by group.
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S_IXGRP Execute (search) by group.
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S_IRWXO Read, write, or execute (search) by others.
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S_IROTH Read by others.
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S_IWOTH Write by others.
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S_IXOTH Execute (search) by others.
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S_ISVTX On directories, restricted deletion flag.
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.TE
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.LP
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The user ID of the file shall be initialized to the effective user
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ID of the process. The group ID of the file shall be
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initialized to either the effective group ID of the process or the
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group ID of the parent directory. Implementations shall provide
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a way to initialize the file's group ID to the group ID of the parent
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directory. Implementations may, but need not, provide an
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implementation-defined way to initialize the file's group ID to the
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effective group ID of the calling process. The owner, group,
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and other permission bits of \fImode\fP shall be modified by the file
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mode creation mask of the process. The \fImknod\fP()
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function shall clear each bit whose corresponding bit in the file
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mode creation mask of the process is set.
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.LP
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If \fIpath\fP names a symbolic link, \fImknod\fP() shall fail and
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set \fIerrno\fP to [EEXIST].
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.LP
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Upon successful completion, \fImknod\fP() shall mark for update the
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\fIst_atime\fP, \fIst_ctime\fP, and \fIst_mtime\fP
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fields of the file. Also, the \fIst_ctime\fP and \fIst_mtime\fP fields
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of the directory that contains the new entry shall be
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marked for update.
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.LP
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Only a process with appropriate privileges may invoke \fImknod\fP()
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for file types other than FIFO-special.
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.SH RETURN VALUE
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.LP
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Upon successful completion, \fImknod\fP() shall return 0. Otherwise,
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it shall return -1, the new file shall not be created, and
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\fIerrno\fP shall be set to indicate the error.
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.SH ERRORS
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.LP
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The \fImknod\fP() function shall fail if:
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.TP 7
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.B EACCES
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A component of the path prefix denies search permission, or write
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permission is denied on the parent directory.
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.TP 7
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.B EEXIST
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The named file exists.
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.TP 7
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.B EINVAL
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An invalid argument exists.
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.TP 7
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.B EIO
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An I/O error occurred while accessing the file system.
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.TP 7
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.B ELOOP
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A loop exists in symbolic links encountered during resolution of the
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\fIpath\fP argument.
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.TP 7
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.B ENAMETOOLONG
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The length of a pathname exceeds {PATH_MAX} or a pathname component
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is longer than {NAME_MAX}.
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.TP 7
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.B ENOENT
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A component of the path prefix specified by \fIpath\fP does not name
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an existing directory or \fIpath\fP is an empty
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string.
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.TP 7
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.B ENOSPC
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The directory that would contain the new file cannot be extended or
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the file system is out of file allocation resources.
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.TP 7
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.B ENOTDIR
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A component of the path prefix is not a directory.
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.TP 7
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.B EPERM
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The invoking process does not have appropriate privileges and the
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file type is not FIFO-special.
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.TP 7
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.B EROFS
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The directory in which the file is to be created is located on a read-only
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file system.
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.sp
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.LP
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The \fImknod\fP() function may fail if:
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.TP 7
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.B ELOOP
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More than {SYMLOOP_MAX} symbolic links were encountered during resolution
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of the \fIpath\fP argument.
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.TP 7
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.B ENAMETOOLONG
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Pathname resolution of a symbolic link produced an intermediate result
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whose length exceeds {PATH_MAX}.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.SS Creating a FIFO Special File
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.LP
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The following example shows how to create a FIFO special file named
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\fB/home/cnd/mod_done\fP, with read/write permissions for
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owner, and with read permissions for group and others.
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.sp
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.RS
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.nf
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\fB#include <sys/types.h>
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#include <sys/stat.h>
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.sp
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dev_t dev;
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int status;
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\&...
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status = mknod("/home/cnd/mod_done", S_IFIFO | S_IWUSR |
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S_IRUSR | S_IRGRP | S_IROTH, dev);
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\fP
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.fi
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.RE
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.SH APPLICATION USAGE
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.LP
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The \fImkfifo\fP() function is preferred over this function for making
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FIFO special
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files.
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.SH RATIONALE
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.LP
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The POSIX.1-1990 standard required that the group ID of a newly created
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file be set to the group ID of its parent directory or
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to the effective group ID of the creating process. FIPS 151-2 required
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that implementations provide a way to have the group ID be
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set to the group ID of the containing directory, but did not prohibit
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implementations also supporting a way to set the group ID to
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the effective group ID of the creating process. Conforming applications
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should not assume which group ID will be used. If it
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matters, an application can use \fIchown\fP() to set the group ID
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after the file is created,
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or determine under what conditions the implementation will set the
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desired group ID.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIchmod\fP() , \fIcreat\fP() , \fIexec\fP() , \fImkdir\fP() , \fImkfifo\fP()
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,
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\fIopen\fP() , \fIstat\fP() , \fIumask\fP() , the Base
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Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<sys/stat.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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