mirror of https://github.com/mkerrisk/man-pages
337 lines
8.5 KiB
Groff
337 lines
8.5 KiB
Groff
.\" Copyright (C) 1993 David Metcalfe (david@prism.demon.co.uk)
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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.\" manual page may be incorrect or out-of-date.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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.\" References consulted:
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.\" Linux libc source code
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.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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.\" 386BSD man pages
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.\" Modified Sat Jul 24 18:26:16 1993 by Rik Faith (faith@cs.unc.edu)
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.\" Modified Thu Apr 11 17:11:33 1996 by Andries Brouwer (aeb@cwi.nl):
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.\" Corrected type of compar routines, as suggested by
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.\" Miguel Barreiro (enano@avalon.yaix.es). Added example.
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.\" Modified Sun Sep 24 20:15:46 2000 by aeb, following Petter Reinholdtsen.
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.\" Modified 2001-12-26 by aeb, following Joey. Added versionsort.
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.\"
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.\" The pieces on scandirat(3) were copyright and licensed as follows.
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.\"
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.\" Copyright (c) 2012, Mark R. Bannister <cambridge@users.sourceforge.net>
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.\" based on text in mkfifoat.3 Copyright (c) 2006, Michael Kerrisk
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.\"
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.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, see
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.\" <http://www.gnu.org/licenses/>.
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.\" %%%LICENSE_END
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.\"
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.TH SCANDIR 3 2021-08-27 "GNU" "Linux Programmer's Manual"
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.SH NAME
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scandir, scandirat, alphasort, versionsort \- scan
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a directory for matching entries
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.SH SYNOPSIS
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.nf
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.B #include <dirent.h>
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.PP
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.BI "int scandir(const char *restrict " dirp ,
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.BI " struct dirent ***restrict " namelist ,
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.BI " int (*" filter ")(const struct dirent *),"
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.BI " int (*" compar ")(const struct dirent **,"
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.BR " const struct dirent **));"
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.PP
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.BI "int alphasort(const struct dirent **" a ", const struct dirent **" b );
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.BI "int versionsort(const struct dirent **" a ", const struct dirent **" b );
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.PP
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.BR "#include <fcntl.h>" " /* Definition of AT_* constants */"
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.B #include <dirent.h>
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.PP
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.BI "int scandirat(int " dirfd ", const char *restrict " dirp ,
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.BI " struct dirent ***restrict " namelist ,
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.BI " int (*" filter ")(const struct dirent *),"
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.BI " int (*" compar ")(const struct dirent **,"
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.BI " const struct dirent **));"
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.fi
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.PP
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.RS -4
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.RE
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.PP
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.BR scandir (),
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.BR alphasort ():
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.nf
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/* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200809L
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|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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.fi
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.PP
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.BR versionsort ():
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.nf
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_GNU_SOURCE
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.fi
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.PP
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.BR scandirat ():
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.nf
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_GNU_SOURCE
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.fi
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.SH DESCRIPTION
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The
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.BR scandir ()
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function scans the directory \fIdirp\fP, calling
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\fIfilter\fP() on each directory entry.
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Entries for which
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\fIfilter\fP() returns nonzero are stored in strings allocated via
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.BR malloc (3),
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sorted using
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.BR qsort (3)
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with the comparison
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function \fIcompar\fP(), and collected in array \fInamelist\fP
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which is allocated via
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.BR malloc (3).
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If \fIfilter\fP is NULL, all entries are selected.
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.PP
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The
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.BR alphasort ()
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and
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.BR versionsort ()
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functions can be used as the comparison function
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.IR compar ().
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The former sorts directory entries using
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.BR strcoll (3),
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the latter using
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.BR strverscmp (3)
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on the strings \fI(*a)\->d_name\fP and \fI(*b)\->d_name\fP.
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.SS scandirat()
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The
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.BR scandirat ()
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function operates in exactly the same way as
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.BR scandir (),
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except for the differences described here.
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.PP
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If the pathname given in
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.I dirp
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is relative, then it is interpreted relative to the directory
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referred to by the file descriptor
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.I dirfd
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(rather than relative to the current working directory of
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the calling process, as is done by
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.BR scandir ()
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for a relative pathname).
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.PP
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If
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.I dirp
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is relative and
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.I dirfd
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is the special value
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.BR AT_FDCWD ,
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then
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.I dirp
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is interpreted relative to the current working
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directory of the calling process (like
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.BR scandir ()).
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.PP
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If
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.I dirp
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is absolute, then
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.I dirfd
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is ignored.
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.PP
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See
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.BR openat (2)
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for an explanation of the need for
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.BR scandirat ().
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.SH RETURN VALUE
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The
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.BR scandir ()
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function returns the number of directory entries
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selected.
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On error, \-1 is returned, with
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.I errno
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set to indicate the error.
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.PP
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The
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.BR alphasort ()
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and
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.BR versionsort ()
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functions return an integer less than, equal to,
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or greater than zero if the first argument is considered to be
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respectively less than, equal to, or greater than the second.
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.SH ERRORS
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.TP
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.B EBADF
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.RB ( scandirat ())
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.I dirp
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is relative but
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.I dirfd
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is neither
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.B AT_FDCWD
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nor a valid file descriptor.
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.TP
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.B ENOENT
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The path in \fIdirp\fR does not exist.
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.TP
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.B ENOMEM
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Insufficient memory to complete the operation.
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.TP
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.B ENOTDIR
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The path in \fIdirp\fR is not a directory.
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.TP
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.B ENOTDIR
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.RB ( scandirat ())
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.I dirp
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is a relative pathname and
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.I dirfd
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is a file descriptor referring to a file other than a directory.
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.SH VERSIONS
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.BR versionsort ()
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was added to glibc in version 2.1.
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.PP
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.BR scandirat ()
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was added to glibc in version 2.15.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.ad l
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.nh
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.TS
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allbox;
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lbx lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR scandir (),
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.BR scandirat ()
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T} Thread safety MT-Safe
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T{
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.BR alphasort (),
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.BR versionsort ()
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T} Thread safety MT-Safe locale
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.TE
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.hy
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.ad
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.sp 1
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.SH CONFORMING TO
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.BR alphasort (),
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.BR scandir ():
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4.3BSD, POSIX.1-2008.
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.PP
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.BR versionsort ()
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and
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.BR scandirat ()
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are GNU extensions.
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.\" .LP
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.\" The functions
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.\" .BR scandir ()
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.\" and
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.\" .BR alphasort ()
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.\" are from 4.3BSD, and have been available under Linux since libc4.
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.\" Libc4 and libc5 use the more precise prototype
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.\" .sp
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.\" .nf
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.\" int alphasort(const struct dirent ** a,
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.\" const struct dirent **b);
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.\" .fi
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.\" .sp
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.\" but glibc 2.0 returns to the imprecise BSD prototype.
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.SH NOTES
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Since glibc 2.1,
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.BR alphasort ()
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calls
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.BR strcoll (3);
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earlier it used
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.BR strcmp (3).
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.PP
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Before glibc 2.10, the two arguments of
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.BR alphasort ()
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and
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.BR versionsort ()
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were typed as
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.IR "const void\ *" .
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When
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.BR alphasort ()
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was standardized in POSIX.1-2008,
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the argument type was specified as the type-safe
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.IR "const struct dirent\ **",
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and glibc 2.10 changed the definition of
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.BR alphasort ()
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(and the nonstandard
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.BR versionsort ())
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to match the standard.
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.SH EXAMPLES
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The program below prints a list of the files in the current directory
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in reverse order.
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.\"
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.SS Program source
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\&
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.EX
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#define _DEFAULT_SOURCE
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#include <dirent.h>
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#include <stdio.h>
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#include <stdlib.h>
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int
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main(void)
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{
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struct dirent **namelist;
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int n;
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n = scandir(".", &namelist, NULL, alphasort);
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if (n == \-1) {
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perror("scandir");
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exit(EXIT_FAILURE);
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}
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while (n\-\-) {
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printf("%s\en", namelist[n]\->d_name);
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free(namelist[n]);
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}
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free(namelist);
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exit(EXIT_SUCCESS);
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}
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.EE
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.SH SEE ALSO
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.BR closedir (3),
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.BR fnmatch (3),
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.BR opendir (3),
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.BR readdir (3),
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.BR rewinddir (3),
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.BR seekdir (3),
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.BR strcmp (3),
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.BR strcoll (3),
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.BR strverscmp (3),
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.BR telldir (3)
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