mirror of https://github.com/mkerrisk/man-pages
134 lines
3.6 KiB
Groff
134 lines
3.6 KiB
Groff
.\" Copyright (C) 1995 Andries Brouwer (aeb@cwi.nl)
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.\" Written 11 June 1995 by Andries Brouwer <aeb@cwi.nl>
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.\" Modified 22 July 1995 by Michael Chastain <mec@duracef.shout.net>:
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.\" In 1.3.X, returns only one entry each time; return value is different.
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.\" Modified 2004-12-01, mtk, fixed headers listed in SYNOPSIS
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.\"
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.TH READDIR 2 2021-03-22 "Linux" "Linux Programmer's Manual"
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.SH NAME
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readdir \- read directory entry
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.SH SYNOPSIS
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.nf
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.BR "#include <sys/syscall.h>" " /* Definition of " SYS_* " constants */"
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.B #include <unistd.h>
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.PP
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.BI "int syscall(SYS_readdir, unsigned int " fd ,
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.BI " struct old_linux_dirent *" dirp ", unsigned int " count );
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.fi
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.PP
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.IR Note :
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There is no definition of
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.BR "struct old_linux_dirent" ;
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see NOTES.
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.SH DESCRIPTION
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This is not the function you are interested in.
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Look at
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.BR readdir (3)
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for the POSIX conforming C library interface.
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This page documents the bare kernel system call interface,
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which is superseded by
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.BR getdents (2).
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.PP
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.BR readdir ()
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reads one
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.I old_linux_dirent
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structure from the directory
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referred to by the file descriptor
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.I fd
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into the buffer pointed to by
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.IR dirp .
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The argument
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.I count
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is ignored; at most one
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.I old_linux_dirent
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structure is read.
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.PP
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The
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.I old_linux_dirent
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structure is declared (privately in Linux kernel file
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.BR fs/readdir.c )
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as follows:
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.PP
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.in +4n
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.EX
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struct old_linux_dirent {
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unsigned long d_ino; /* inode number */
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unsigned long d_offset; /* offset to this \fIold_linux_dirent\fP */
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unsigned short d_namlen; /* length of this \fId_name\fP */
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char d_name[1]; /* filename (null\-terminated) */
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}
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.EE
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.in
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.PP
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.I d_ino
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is an inode number.
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.I d_offset
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is the distance from the start of the directory to this
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.IR old_linux_dirent .
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.I d_reclen
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is the size of
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.IR d_name ,
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not counting the terminating null byte (\(aq\e0\(aq).
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.I d_name
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is a null-terminated filename.
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.SH RETURN VALUE
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On success, 1 is returned.
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On end of directory, 0 is returned.
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On error, \-1 is returned, and
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.I errno
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is set to indicate the error.
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.SH ERRORS
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.TP
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.B EBADF
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Invalid file descriptor
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.IR fd .
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.TP
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.B EFAULT
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Argument points outside the calling process's address space.
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.TP
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.B EINVAL
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Result buffer is too small.
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.TP
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.B ENOENT
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No such directory.
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.TP
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.B ENOTDIR
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File descriptor does not refer to a directory.
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.SH CONFORMING TO
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This system call is Linux-specific.
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.SH NOTES
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You will need to define the
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.I old_linux_dirent
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structure yourself.
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However, probably you should use
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.BR readdir (3)
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instead.
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.PP
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This system call does not exist on x86-64.
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.SH SEE ALSO
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.BR getdents (2),
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.BR readdir (3)
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