.\" and copyright (c) 2006 Justin Pryzby <justinpryzby@users.sf.net>
.\" and copyright (c) 2006 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
-.\" This is free documentation; you can redistribute it and/or
-.\" modify it under the terms of the GNU General Public License as
-.\" published by the Free Software Foundation; either version 2 of
-.\" the License, or (at your option) any later version.
-.\"
-.\" The GNU General Public License's references to "object code"
-.\" and "executables" are to be interpreted as the output of any
-.\" document formatting or typesetting system, including
-.\" intermediate and printed output.
-.\"
-.\" This manual is distributed in the hope that it will be useful,
-.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
-.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-.\" GNU General Public License for more details.
-.\"
-.\" You should have received a copy of the GNU General Public
-.\" License along with this manual; if not, write to the Free
-.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
-.\" USA.
+.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\" Modified Sun Jul 25 11:02:22 1993 by Rik Faith (faith@cs.unc.edu)
.\" 2006-05-24, Justin Pryzby <justinpryzby@users.sf.net>
-.\" document FTW_ACTIONRETVAL; include .SH "RETURN VALUE";
+.\" document FTW_ACTIONRETVAL; include .SH RETURN VALUE;
.\" 2006-05-24, Justin Pryzby <justinpryzby@users.sf.net> and
.\" Michael Kerrisk <mtk.manpages@gmail.com>
.\" reorganized and rewrote much of the page
.\" 2006-05-24, Michael Kerrisk <mtk.manpages@gmail.com>
.\" Added an example program.
-.TH FTW 3 2008-08-06 "Linux" "Linux Programmer's Manual"
+.\"
+.TH FTW 3 2021-03-22 "Linux man-pages (unreleased)" "Linux Programmer's Manual"
.SH NAME
ftw, nftw \- file tree walk
+.SH LIBRARY
+Standard C library
+.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <ftw.h>
-.sp
-.BI "int ftw(const char *" dirpath ,
-.BI " int (*" fn ") (const char *" fpath ", const struct stat *" sb ,
-.BI " int " typeflag ),
-.BI " int " nopenfd );
-.sp
-.B #define _XOPEN_SOURCE 500
-.B #include <ftw.h>
-.sp
+.PP
.BI "int nftw(const char *" dirpath ,
-.BI " int (*" fn ") (const char *" fpath ", const struct stat *" sb ,
-.BI " int " typeflag ", struct FTW *" ftwbuf ),
+.BI " int (*" fn ")(const char *" fpath ", const struct stat *" sb ,
+.BI " int " typeflag ", struct FTW *" ftwbuf ),
.BI " int " nopenfd ", int " flags );
+.PP
+.BI "int ftw(const char *" dirpath ,
+.BI " int (*" fn ")(const char *" fpath ", const struct stat *" sb ,
+.BI " int " typeflag ),
+.BI " int " nopenfd );
+.fi
+.PP
+.RS -4
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.RE
+.PP
+.BR nftw ():
+.nf
+ _XOPEN_SOURCE >= 500
.fi
.SH DESCRIPTION
-.BR ftw ()
+.BR nftw ()
walks through the directory tree that is
located under the directory \fIdirpath\fP,
and calls \fIfn\fP() once for each entry in the tree.
By default, directories are handled before the files and
-subdirectories they contain (pre-order traversal).
-
+subdirectories they contain (preorder traversal).
+.PP
To avoid using up all of the calling process's file descriptors,
\fInopenfd\fP specifies the maximum number of directories that
-.BR ftw ()
+.BR nftw ()
will hold open simultaneously.
When
the search depth exceeds this,
-.BR ftw ()
+.BR nftw ()
will become slower because
directories have to be closed and reopened.
-.BR ftw ()
+.BR nftw ()
uses at most
one file descriptor for each level in the directory tree.
-
+.PP
For each entry found in the tree,
-.BR ftw ()
+.BR nftw ()
calls
-\fIfn\fP() with three arguments:
+\fIfn\fP() with four arguments:
.IR fpath ,
.IR sb ,
+.IR typeflag ,
and
-.IR typeflag .
+.IR ftwbuf .
.I fpath
-is the pathname of the entry relative to
-.IR dirpath .
+is the pathname of the entry,
+and is expressed either as a pathname relative to the calling process's
+current working directory at the time of the call to
+.BR nftw (),
+if
+.I dirpath
+was expressed as a relative pathname,
+or as an absolute pathname, if
+.I dirpath
+was expressed as an absolute pathname.
.I sb
is a pointer to the
.I stat
.BR stat (2)
for
.IR fpath .
+.PP
+The
.I typeflag
+argument passed to
+.IR fn ()
is an integer that has one of the following values:
.TP
.B FTW_F
.I fpath
is a directory which can't be read.
.TP
+.B FTW_DP
+.I fpath
+is a directory, and \fBFTW_DEPTH\fP was specified in \fIflags\fP.
+(If
+.B FTW_DEPTH
+was not specified in
+.IR flags ,
+then directories will always be visited with
+.I typeflag
+set to
+.BR FTW_D .)
+All of the files
+and subdirectories within \fIfpath\fP have been processed.
+.TP
.B FTW_NS
The
.BR stat (2)
call failed on
.IR fpath ,
which is not a symbolic link.
-.sp
-If
+The probable cause for this is that the caller had read permission
+on the parent directory, so that the filename
.I fpath
-is a symbolic link and
-.BR stat (2)
-failed, POSIX.1-2001 states
-that it is undefined whether \fBFTW_NS\fP or \fBFTW_SL\fP (see below)
-is passed in
-.IR typeflag .
+could be seen,
+but did not have execute permission,
+so that the file could not be reached for
+.BR stat (2).
+The contents of the buffer pointed to by
+.I sb
+are undefined.
+.TP
+.B FTW_SL
+.I fpath
+is a symbolic link, and \fBFTW_PHYS\fP was set in \fIflags\fP.
+.\" To obtain the definition of this constant from
+.\" .IR <ftw.h> ,
+.\" either
+.\" .B _BSD_SOURCE
+.\" must be defined, or
+.\" .BR _XOPEN_SOURCE
+.\" must be defined with a value of 500 or more.
+.TP
+.B FTW_SLN
+.I fpath
+is a symbolic link pointing to a nonexistent file.
+(This occurs only if \fBFTW_PHYS\fP is not set.)
+In this case the
+.I sb
+argument passed to
+.IR fn ()
+contains information returned by performing
+.BR lstat (2)
+on the "dangling" symbolic link.
+(But see BUGS.)
+.PP
+The fourth argument
+.RI ( ftwbuf )
+that
+.BR nftw ()
+supplies when calling
+\fIfn\fP()
+is a pointer to a structure of type \fIFTW\fP:
+.PP
+.in +4n
+.EX
+struct FTW {
+ int base;
+ int level;
+};
+.EE
+.in
+.PP
+.I base
+is the offset of the filename (i.e., basename component)
+in the pathname given in
+.IR fpath .
+.I level
+is the depth of
+.I fpath
+in the directory tree, relative to the root of the tree
+.RI ( dirpath ,
+which has depth 0).
.PP
To stop the tree walk, \fIfn\fP() returns a nonzero value; this
value will become the return value of
-.BR ftw ().
+.BR nftw ().
As long as \fIfn\fP() returns 0,
-.BR ftw ()
+.BR nftw ()
will continue either until it has traversed the entire tree,
in which case it will return zero,
or until it encounters an error (such as a
failure), in which case it will return \-1.
.PP
Because
-.BR ftw ()
+.BR nftw ()
uses dynamic data structures, the only safe way to
exit out of a tree walk is to return a nonzero value from \fIfn\fP().
To allow a signal to terminate the walk without causing a memory leak,
\fIDon't\fP use
.BR longjmp (3)
unless the program is going to terminate.
-.SS nftw()
-The function
+.PP
+The \fIflags\fP argument of
.BR nftw ()
-is the same as
-.BR ftw (),
-except that it has one additional argument, \fIflags\fP,
-and calls \fIfn\fP() with one more argument, \fIftwbuf\fP.
-
-This \fIflags\fP argument is formed by ORing zero or more of the
+is formed by ORing zero or more of the
following flags:
.TP
.BR FTW_ACTIONRETVAL " (since glibc 2.3.3)"
.PP
Other return values could be associated with new actions in the future;
\fIfn\fP() should not return values other than those listed above.
-
+.PP
The feature test macro
.B _GNU_SOURCE
-must be defined in order to
+must be defined
+(before including
+.I any
+header files)
+in order to
obtain the definition of \fBFTW_ACTIONRETVAL\fP from \fI<ftw.h>\fP.
.RE
.TP
to each directory before handling its contents.
This is useful if the program needs to perform some action
in the directory in which \fIfpath\fP resides.
+(Specifying this flag has no effect on the pathname that is passed in the
+.I fpath
+argument of
+.IR fn .)
.TP
.B FTW_DEPTH
If set, do a post-order traversal, that is, call \fIfn\fP() for
(By default, each directory is handled \fIbefore\fP its contents.)
.TP
.B FTW_MOUNT
-If set, stay within the same file system
+If set, stay within the same filesystem
(i.e., do not cross mount points).
.TP
.B FTW_PHYS
If set, do not follow symbolic links.
(This is what you want.)
If not set, symbolic links are followed, but no file is reported twice.
-.sp
+.IP
If \fBFTW_PHYS\fP is not set, but \fBFTW_DEPTH\fP is set,
then the function
.IR fn ()
is never called for a directory that would be a descendant of itself.
-.LP
-For each entry in the directory tree,
+.SS ftw()
+.BR ftw ()
+is an older function that offers a subset of the functionality of
+.BR nftw ().
+The notable differences are as follows:
+.IP * 3
+.BR ftw ()
+has no
+.I flags
+argument.
+It behaves the same as when
.BR nftw ()
-calls
-.IR fn ()
-with four arguments.
-.I fpath
-and
-.I sb
-are as for
-.BR ftw ().
+is called with
+.I flags
+specified as zero.
+.IP *
+The callback function,
+.IR fn (),
+is not supplied with a fourth argument.
+.IP *
+The range of values that is passed via the
.I typeflag
-may receive any of the same values as with
-.BR ftw (),
-or any of the following values:
-.TP
-.B FTW_DP
-.I fpath
-is a directory, and \fBFTW_DEPTH\fP was specified in \fIflags\fP.
-All of the files
-and subdirectories within \fIfpath\fP have been processed.
-.TP
-.B FTW_SL
-.I fpath
-is a symbolic link, and \fBFTW_PHYS\fP was set in \fIflags\fP.
-.\" To obtain the definition of this constant from
-.\" .IR <ftw.h> ,
-.\" either
-.\" .B _BSD_SOURCE
-.\" must be defined, or
-.\" .BR _XOPEN_SOURCE
-.\" must be defined with a value of 500 or more.
-.TP
-.B FTW_SLN
-.I fpath
-is a symbolic link pointing to a nonexistent file.
-(This occurs only if \fBFTW_PHYS\fP is not set.)
-.LP
-The fourth argument that
-.BR nftw ()
-supplies when calling
-\fIfn\fP()
-is a structure of type \fIFTW\fP:
-.in +4n
-.nf
-
-struct FTW {
- int base;
- int level;
-};
-
-.fi
-.in
-.I base
-is the offset of the filename (i.e., basename component)
-in the pathname given in
-.IR fpath .
-.I level
-is the depth of
-.I fpath
-in the directory tree, relative to the root of the tree
-.RI ( dirpath ,
-which has depth 0).
-.SH "RETURN VALUE"
+argument supplied to
+.IR fn ()
+is smaller: just
+.BR FTW_F ,
+.BR FTW_D ,
+.BR FTW_DNR ,
+.BR FTW_NS ,
+and (possibly)
+.BR FTW_SL .
+.SH RETURN VALUE
These functions return 0 on success, and \-1 if an error occurs.
-
+.PP
If \fIfn\fP() returns nonzero,
then the tree walk is terminated and the value returned by \fIfn\fP()
is returned as the result of
.BR ftw ()
or
.BR nftw ().
-
+.PP
If
.BR nftw ()
is called with the \fBFTW_ACTIONRETVAL\fP flag,
to terminate the tree walk is \fBFTW_STOP\fP,
and that value is returned as the result of
.BR nftw ().
-.SH "CONFORMING TO"
-POSIX.1-2001, SVr4, SUSv1.
+.SH VERSIONS
+.BR nftw ()
+is available under glibc since version 2.1.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.ad l
+.nh
+.TS
+allbox;
+lbx lb lb
+l l l.
+Interface Attribute Value
+T{
+.BR nftw ()
+T} Thread safety MT-Safe cwd
+T{
+.BR ftw ()
+T} Thread safety MT-Safe
+.TE
+.hy
+.ad
+.sp 1
+.SH STANDARDS
+POSIX.1-2001, POSIX.1-2008, SVr4, SUSv1.
POSIX.1-2008 marks
.BR ftw ()
as obsolete.
.SH NOTES
+POSIX.1-2008 notes that the results are unspecified if
+.I fn
+does not preserve the current working directory.
+.PP
The function
.BR nftw ()
and the use of \fBFTW_SL\fP with
.BR ftw ()
were introduced in SUSv1.
-.LP
-On some systems
+.PP
+In some implementations (e.g., glibc),
.BR ftw ()
will never use \fBFTW_SL\fP, on other systems \fBFTW_SL\fP occurs only
for symbolic links that do not point to an existing file,
and again on other systems
.BR ftw ()
will use \fBFTW_SL\fP for each symbolic link.
-For predictable control, use
+If
+.I fpath
+is a symbolic link and
+.BR stat (2)
+failed, POSIX.1-2008 states
+that it is undefined whether \fBFTW_NS\fP or \fBFTW_SL\fP
+is passed in
+.IR typeflag .
+For predictable results, use
.BR nftw ().
-.LP
-Under Linux, libc4 and libc5 and glibc 2.0.6 will
-use \fBFTW_F\fP for all objects (files, symbolic links, FIFOs, etc.)
-that can be stat'ed but are not a directory.
-
-The function
-.BR nftw ()
-is available since glibc 2.1.
-
-\fBFTW_ACTIONRETVAL\fP is glibc-specific.
-.SH EXAMPLE
+.SH BUGS
+According to POSIX.1-2008, when the
+.I typeflag
+argument passed to
+.IR fn ()
+contains
+.BR FTW_SLN ,
+the buffer pointed to by
+.I sb
+should contain information about the dangling symbolic link
+(obtained by calling
+.BR lstat (2)
+on the link).
+Early glibc versions correctly followed the POSIX specification on this point.
+However, as a result of a regression introduced in glibc 2.4,
+the contents of the buffer pointed to by
+.I sb
+were undefined when
+.B FTW_SLN
+is passed in
+.IR typeflag .
+(More precisely, the contents of the buffer were left unchanged in this case.)
+This regression was eventually fixed in glibc 2.30,
+.\" https://bugzilla.redhat.com/show_bug.cgi?id=1422736
+.\" http://austingroupbugs.net/view.php?id=1121
+.\" glibc commit 6ba205b2c35e3e024c8c12d2ee1b73363e84da87
+.\" https://sourceware.org/bugzilla/show_bug.cgi?id=23501
+so that the glibc implementation (once more) follows the POSIX specification.
+.SH EXAMPLES
The following program traverses the directory tree under the path named
in its first command-line argument, or under the current directory
if no argument is supplied.
control the value assigned to the \fIflags\fP
argument when calling
.BR nftw ().
-.nf
-
+.SS Program source
+\&
+.EX
#define _XOPEN_SOURCE 500
#include <ftw.h>
#include <stdio.h>
display_info(const char *fpath, const struct stat *sb,
int tflag, struct FTW *ftwbuf)
{
- printf("%\-3s %2d %7jd %\-40s %d %s\\n",
- (tflag == FTW_D) ? "d" : (tflag == FTW_DNR) ? "dnr" :
- (tflag == FTW_DP) ? "dp" : (tflag == FTW_F) ? "f" :
- (tflag == FTW_NS) ? "ns" : (tflag == FTW_SL) ? "sl" :
- (tflag == FTW_SLN) ? "sln" : "???",
- ftwbuf\->level, (intmax_t) sb\->st_size,
- fpath, ftwbuf\->base, fpath + ftwbuf\->base);
+ printf("%\-3s %2d ",
+ (tflag == FTW_D) ? "d" : (tflag == FTW_DNR) ? "dnr" :
+ (tflag == FTW_DP) ? "dp" : (tflag == FTW_F) ? "f" :
+ (tflag == FTW_NS) ? "ns" : (tflag == FTW_SL) ? "sl" :
+ (tflag == FTW_SLN) ? "sln" : "???",
+ ftwbuf\->level);
+
+ if (tflag == FTW_NS)
+ printf("\-\-\-\-\-\-\-");
+ else
+ printf("%7jd", (intmax_t) sb\->st_size);
+
+ printf(" %\-40s %d %s\en",
+ fpath, ftwbuf\->base, fpath + ftwbuf\->base);
+
return 0; /* To tell nftw() to continue */
}
perror("nftw");
exit(EXIT_FAILURE);
}
+
exit(EXIT_SUCCESS);
}
-.fi
-.SH "SEE ALSO"
+.EE
+.SH SEE ALSO
.BR stat (2),
.BR fts (3),
-.BR readdir (3),
-.BR feature_test_macros (7)
+.BR readdir (3)
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