mirror of https://github.com/mkerrisk/man-pages
521 lines
13 KiB
Groff
521 lines
13 KiB
Groff
.\" Copyright (c) 1993 Michael Haardt (michael@moria.de)
|
|
.\" and copyright (c) 1999 Andries Brouwer (aeb@cwi.nl)
|
|
.\" and copyright (c) 2006 Justin Pryzby <justinpryzby@users.sf.net>
|
|
.\" and copyright (c) 2006 Michael Kerrisk <mtk.manpages@gmail.com>
|
|
.\"
|
|
.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
|
|
.\" 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, see
|
|
.\" <http://www.gnu.org/licenses/>.
|
|
.\" %%%LICENSE_END
|
|
.\"
|
|
.\" 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;
|
|
.\" 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 2017-07-13 "Linux" "Linux Programmer's Manual"
|
|
.SH NAME
|
|
ftw, nftw \- file tree walk
|
|
.SH SYNOPSIS
|
|
.nf
|
|
.B #include <ftw.h>
|
|
.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 " nopenfd ", int " flags );
|
|
.PP
|
|
.B #include <ftw.h>
|
|
.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
|
|
.in -4n
|
|
Feature Test Macro Requirements for glibc (see
|
|
.BR feature_test_macros (7)):
|
|
.in
|
|
.PP
|
|
.BR nftw ():
|
|
_XOPEN_SOURCE >= 500
|
|
.SH DESCRIPTION
|
|
.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 (preorder traversal).
|
|
|
|
To avoid using up all of the calling process's file descriptors,
|
|
\fInopenfd\fP specifies the maximum number of directories that
|
|
.BR nftw ()
|
|
will hold open simultaneously.
|
|
When
|
|
the search depth exceeds this,
|
|
.BR nftw ()
|
|
will become slower because
|
|
directories have to be closed and reopened.
|
|
.BR nftw ()
|
|
uses at most
|
|
one file descriptor for each level in the directory tree.
|
|
|
|
For each entry found in the tree,
|
|
.BR nftw ()
|
|
calls
|
|
\fIfn\fP() with four arguments:
|
|
.IR fpath ,
|
|
.IR sb ,
|
|
.IR typeflag ,
|
|
and
|
|
.IR ftwbuf .
|
|
.I fpath
|
|
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
|
|
.IR 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
|
|
structure returned by a call to
|
|
.BR stat (2)
|
|
for
|
|
.IR fpath .
|
|
|
|
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 regular file.
|
|
.TP
|
|
.B FTW_D
|
|
.I fpath
|
|
is a directory.
|
|
.TP
|
|
.B FTW_DNR
|
|
.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.
|
|
The probable cause for this is that the caller had read permission
|
|
on the parent directory, so that the filename
|
|
.I fpath
|
|
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.)
|
|
On most implementations, in this case the
|
|
.I sb
|
|
argument passed to
|
|
.IR fn ()
|
|
contains information returned by performing
|
|
.BR lstat (2)
|
|
on the symbolic link.
|
|
For the details on Linux, 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:
|
|
.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).
|
|
.PP
|
|
To stop the tree walk, \fIfn\fP() returns a nonzero value; this
|
|
value will become the return value of
|
|
.BR nftw ().
|
|
As long as \fIfn\fP() returns 0,
|
|
.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
|
|
.BR malloc (3)
|
|
failure), in which case it will return \-1.
|
|
.PP
|
|
Because
|
|
.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,
|
|
have the handler set a global flag that is checked by \fIfn\fP().
|
|
\fIDon't\fP use
|
|
.BR longjmp (3)
|
|
unless the program is going to terminate.
|
|
|
|
The \fIflags\fP argument of
|
|
.BR nftw ()
|
|
is formed by ORing zero or more of the
|
|
following flags:
|
|
.TP
|
|
.BR FTW_ACTIONRETVAL " (since glibc 2.3.3)"
|
|
If this glibc-specific flag is set, then
|
|
.BR nftw ()
|
|
handles the return value from
|
|
.IR fn ()
|
|
differently.
|
|
.IR fn ()
|
|
should return one of the following values:
|
|
.RS
|
|
.TP
|
|
.B FTW_CONTINUE
|
|
Instructs
|
|
.BR nftw ()
|
|
to continue normally.
|
|
.TP
|
|
.B FTW_SKIP_SIBLINGS
|
|
If \fIfn\fP() returns this value, then
|
|
siblings of the current entry will be skipped,
|
|
and processing continues in the parent.
|
|
.\" If \fBFTW_DEPTH\fP
|
|
.\" is set, the entry's parent directory is processed next (with
|
|
.\" \fIflag\fP set to \fBFTW_DP\fP).
|
|
.TP
|
|
.B FTW_SKIP_SUBTREE
|
|
If \fIfn\fP() is called with an entry that is a directory
|
|
(\fItypeflag\fP is \fBFTW_D\fP), this return
|
|
value will prevent objects within that directory from being passed as
|
|
arguments to \fIfn\fP().
|
|
.BR nftw ()
|
|
continues processing with the next sibling of the directory.
|
|
.TP
|
|
.B FTW_STOP
|
|
Causes
|
|
.BR nftw ()
|
|
to return immediately with the return value
|
|
\fBFTW_STOP\fP.
|
|
.PP
|
|
Other return values could be associated with new actions in the future;
|
|
\fIfn\fP() should not return values other than those listed above.
|
|
|
|
The feature test macro
|
|
.B _GNU_SOURCE
|
|
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
|
|
.B FTW_CHDIR
|
|
If set, do a
|
|
.BR chdir (2)
|
|
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
|
|
the directory itself \fIafter\fP handling the contents of the directory
|
|
and its subdirectories.
|
|
(By default, each directory is handled \fIbefore\fP its contents.)
|
|
.TP
|
|
.B FTW_MOUNT
|
|
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
|
|
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.
|
|
.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
|
|
.IR flags
|
|
argument.
|
|
It behaves the same as when
|
|
.BR nftw ()
|
|
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
|
|
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.
|
|
|
|
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 ().
|
|
|
|
If
|
|
.BR nftw ()
|
|
is called with the \fBFTW_ACTIONRETVAL\fP flag,
|
|
then the only nonzero value that should be used by \fIfn\fP()
|
|
to terminate the tree walk is \fBFTW_STOP\fP,
|
|
and that value is returned as the result of
|
|
.BR nftw ().
|
|
.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).
|
|
.TS
|
|
allbox;
|
|
lb 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
|
|
|
|
.SH CONFORMING TO
|
|
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
|
|
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.
|
|
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 ().
|
|
.SH EXAMPLE
|
|
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.
|
|
It displays various information about each file.
|
|
The second command-line argument can be used to specify characters that
|
|
control the value assigned to the \fIflags\fP
|
|
argument when calling
|
|
.BR nftw ().
|
|
.SS Program source
|
|
.nf
|
|
#define _XOPEN_SOURCE 500
|
|
#include <ftw.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <stdint.h>
|
|
|
|
static int
|
|
display_info(const char *fpath, const struct stat *sb,
|
|
int tflag, struct FTW *ftwbuf)
|
|
{
|
|
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\\n",
|
|
fpath, ftwbuf\->base, fpath + ftwbuf\->base);
|
|
|
|
return 0; /* To tell nftw() to continue */
|
|
}
|
|
|
|
int
|
|
main(int argc, char *argv[])
|
|
{
|
|
int flags = 0;
|
|
|
|
if (argc > 2 && strchr(argv[2], \(aqd\(aq) != NULL)
|
|
flags |= FTW_DEPTH;
|
|
if (argc > 2 && strchr(argv[2], \(aqp\(aq) != NULL)
|
|
flags |= FTW_PHYS;
|
|
|
|
if (nftw((argc < 2) ? "." : argv[1], display_info, 20, flags)
|
|
== \-1) {
|
|
perror("nftw");
|
|
exit(EXIT_FAILURE);
|
|
}
|
|
|
|
exit(EXIT_SUCCESS);
|
|
}
|
|
.fi
|
|
.SH BUGS
|
|
In the specification of
|
|
.BR nftw (),
|
|
POSIX.1 notes that when
|
|
.B FTW_NS
|
|
is passed as the
|
|
.I typeflag
|
|
argument of
|
|
.IR fn (),
|
|
then the contents of the buffer pointed to by the
|
|
.I sb
|
|
argument are undefined.
|
|
The standard makes no such statement for the case where
|
|
.B FTW_SLN
|
|
is passed in
|
|
.IR typeflag ,
|
|
with the implication that the contents of the buffer pointed to by
|
|
.I sb
|
|
are defined.
|
|
And indeed this is the case on most implementations: the buffer pointed to by
|
|
.I sb
|
|
contains the results produced by applying
|
|
.BR lstat (2)
|
|
to the symbolic link.
|
|
In early glibc, the behavior was the same.
|
|
However, since glibc 2.4, the contents of the buffer pointed to by
|
|
.I sb
|
|
are undefined when
|
|
.B FTW_SLN
|
|
is passed in
|
|
.IR typeflag .
|
|
This change
|
|
.I appears
|
|
to be an unintended regression,
|
|
but it is not (yet) clear if the behavior will be restored to that
|
|
provided in the original glibc implementation (and on other implementations).
|
|
.\" FIXME .
|
|
.\" https://bugzilla.redhat.com/show_bug.cgi?id=1422736
|
|
.\" http://austingroupbugs.net/view.php?id=1121
|
|
.SH SEE ALSO
|
|
.BR stat (2),
|
|
.BR fts (3),
|
|
.BR readdir (3)
|