mirror of https://github.com/mkerrisk/man-pages
172 lines
4.5 KiB
Groff
172 lines
4.5 KiB
Groff
.\" Copyright (C) 1993 David Metcalfe (david@prism.demon.co.uk)
|
|
.\"
|
|
.\" Permission is granted to make and distribute verbatim copies of this
|
|
.\" manual provided the copyright notice and this permission notice are
|
|
.\" preserved on all copies.
|
|
.\"
|
|
.\" Permission is granted to copy and distribute modified versions of this
|
|
.\" manual under the conditions for verbatim copying, provided that the
|
|
.\" entire resulting derived work is distributed under the terms of a
|
|
.\" permission notice identical to this one.
|
|
.\"
|
|
.\" Since the Linux kernel and libraries are constantly changing, this
|
|
.\" manual page may be incorrect or out-of-date. The author(s) assume no
|
|
.\" responsibility for errors or omissions, or for damages resulting from
|
|
.\" the use of the information contained herein. The author(s) may not
|
|
.\" have taken the same level of care in the production of this manual,
|
|
.\" which is licensed free of charge, as they might when working
|
|
.\" professionally.
|
|
.\"
|
|
.\" Formatted or processed versions of this manual, if unaccompanied by
|
|
.\" the source, must acknowledge the copyright and authors of this work.
|
|
.\"
|
|
.\" References consulted:
|
|
.\" Linux libc source code
|
|
.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
|
|
.\" 386BSD man pages
|
|
.\" Modified Sat Jul 24 16:09:49 1993 by Rik Faith (faith@cs.unc.edu)
|
|
.\" Modified 11 June 1995 by Andries Brouwer (aeb@cwi.nl)
|
|
.\" Modified 22 July 1996 by Andries Brouwer (aeb@cwi.nl)
|
|
.\" 2007-07-30 Ulrich Drepper <drepper@redhat.com>, mtk:
|
|
.\" Rework discussion of non-standard structure fields.
|
|
.\"
|
|
.TH READDIR 3 2007-07-30 "" "Linux Programmer's Manual"
|
|
.SH NAME
|
|
readdir \- read a directory
|
|
.SH SYNOPSIS
|
|
.nf
|
|
.B #include <sys/types.h>
|
|
.sp
|
|
.B #include <dirent.h>
|
|
.sp
|
|
.BI "struct dirent *readdir(DIR *" dir );
|
|
.fi
|
|
.SH DESCRIPTION
|
|
The
|
|
.BR readdir ()
|
|
function returns a pointer to a \fIdirent\fP structure
|
|
representing the next directory entry in the directory stream pointed
|
|
to by \fIdir\fP.
|
|
It returns NULL on reaching the end-of-file or if
|
|
an error occurred.
|
|
.PP
|
|
On Linux, the
|
|
.I dirent
|
|
structure is defined as follows:
|
|
.PP
|
|
.RS 0.25i
|
|
.nf
|
|
struct dirent {
|
|
ino_t d_ino; /* inode number */
|
|
off_t d_off; /* offset to the next dirent */
|
|
unsigned short d_reclen; /* length of this record */
|
|
unsigned char d_type; /* type of file */
|
|
char d_name[256]; /* filename */
|
|
};
|
|
.fi
|
|
.RE
|
|
.PP
|
|
According to POSIX, the
|
|
.I dirent
|
|
structure contains a field
|
|
.I "char d_name[]"
|
|
of unspecified size, with at most
|
|
.B NAME_MAX
|
|
characters preceding the terminating null byte.
|
|
POSIX.1-2001 also documents the field
|
|
.I "ino_t d_ino"
|
|
as an XSI extension.
|
|
The other fields are unstandardized, and not present on all systems;
|
|
see NOTES below for some further details.
|
|
.PP
|
|
The data returned by
|
|
.BR readdir ()
|
|
may be overwritten by subsequent calls to
|
|
.BR readdir ()
|
|
for the same directory stream.
|
|
.SH "RETURN VALUE"
|
|
The
|
|
.BR readdir ()
|
|
function returns a pointer to a
|
|
.I dirent
|
|
structure, or
|
|
NULL if an error occurs or end-of-file is reached.
|
|
On error,
|
|
.I errno
|
|
is set appropriately.
|
|
.SH ERRORS
|
|
.TP
|
|
.B EBADF
|
|
Invalid directory stream descriptor \fIdir\fP.
|
|
.SH "CONFORMING TO"
|
|
SVr4, 4.3BSD, POSIX.1-2001
|
|
.SH NOTES
|
|
Only the fields
|
|
.I d_name
|
|
and
|
|
.I d_ino
|
|
are specified in POSIX.1-2001.
|
|
The remaining fields are available on many, but not all systems.
|
|
Under glibc,
|
|
programs can check for the availability of the fields not defined
|
|
in POSIX.1 by testing whether the macros
|
|
.BR _DIRENT_HAVE_D_NAMLEN ,
|
|
.BR _DIRENT_HAVE_D_RECLEN ,
|
|
.BR _DIRENT_HAVE_D_OFF ,
|
|
or
|
|
.B _DIRENT_HAVE_D_TYPE
|
|
are defined.
|
|
|
|
Other than Linux, the
|
|
.I d_type
|
|
field is available mainly only on BSD systems.
|
|
This field makes it possible to avoid the expense of calling
|
|
.BR stat (2)
|
|
if further
|
|
actions depend on the type of the file.
|
|
If the
|
|
.B _BSD_SOURCE
|
|
feature test macro is defined,
|
|
then glibc defines the following macro constants
|
|
for the value returned in
|
|
.IR d_type :
|
|
.TP 12
|
|
.B DT_UNKNOWN
|
|
The file type is unknown.
|
|
.\" The glibc manual says that on some systems this is the only
|
|
.\" value returned
|
|
.TP
|
|
.B DT_REG
|
|
This is a regular file.
|
|
.TP
|
|
.B DT_DIR
|
|
This is a directory.
|
|
.TP
|
|
.B DT_FIFO
|
|
This is a named pipe, or FIFO.
|
|
.TP
|
|
.B DT_SOCK
|
|
This is a Unix domain socket.
|
|
.TP
|
|
.B DT_CHR
|
|
This is a character device.
|
|
.TP
|
|
.B DT_BLK
|
|
This is a block device.
|
|
.PP
|
|
If the file type could not be determined, the value
|
|
.B DT_UNKNOWN
|
|
is returned in
|
|
.IR d_type .
|
|
.SH "SEE ALSO"
|
|
.BR read (2),
|
|
.BR closedir (3),
|
|
.BR dirfd (3),
|
|
.BR ftw (3),
|
|
.BR opendir (3),
|
|
.BR rewinddir (3),
|
|
.BR scandir (3),
|
|
.BR seekdir (3),
|
|
.BR telldir (3),
|
|
.BR feature_test_macros (7)
|