'\" et

.TH NFTW "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH PROLOG

This manual page is part of the POSIX Programmer's Manual.

The Linux implementation of this interface may differ (consult

the corresponding Linux manual page for details of Linux behavior),

or the interface may not be implemented on Linux.

.SH NAME

nftw

\(em walk a file tree

.SH SYNOPSIS

.LP

.nf

#include <ftw.h>

.P

int nftw(const char *\fIpath\fP, int (*\fIfn\fP)(const char *,

    const struct stat *, int, struct FTW *), int \fIfd_limit\fP, int \fIflags\fP);

.fi

.SH DESCRIPTION

The

\fInftw\fR()

function shall recursively descend the directory hierarchy rooted in

.IR path .

The

\fInftw\fR()

function has a similar effect to

\fIftw\fR()

except that it takes an additional argument

.IR flags ,

which is a bitwise-inclusive OR of zero or more of the following flags:

.IP FTW_CHDIR 12

If set,

\fInftw\fR()

shall change the current working directory to each directory as it

reports files in that directory. If clear,

\fInftw\fR()

shall not change the current working directory.

.IP FTW_DEPTH 12

If set,

\fInftw\fR()

shall report all files in a directory before reporting the directory

itself. If clear,

\fInftw\fR()

shall report any directory before reporting the files in that directory.

.IP FTW_MOUNT 12

If set,

\fInftw\fR()

shall only report files in the same file system as

.IR path .

If clear,

\fInftw\fR()

shall report all files encountered during the walk.

.IP FTW_PHYS 12

If set,

\fInftw\fR()

shall perform a physical walk and shall not follow symbolic links.

.P

If FTW_PHYS is clear and FTW_DEPTH is set,

\fInftw\fR()

shall follow links instead of reporting them, but shall not report any

directory that would be a descendant of itself. If FTW_PHYS is clear

and FTW_DEPTH is clear,

\fInftw\fR()

shall follow links instead of reporting them, but shall not report the

contents of any directory that would be a descendant of itself.

.P

At each file it encounters,

\fInftw\fR()

shall call the user-supplied function

.IR fn

with four arguments:

.IP " *" 4

The first argument is the pathname of the object.

.IP " *" 4

The second argument is a pointer to the

.BR stat

buffer containing information on the object, filled in as if

\fIfstatat\fR(),

\fIstat\fR(),

or

\fIlstat\fR()

had been called to retrieve the information.

.IP " *" 4

The third argument is an integer giving additional information. Its

value is one of the following:

.RS 4 

.IP FTW_D 10

The object is a directory.

.IP FTW_DNR 10

The object is a directory that cannot be read. The

.IR fn

function shall not be called for any of its descendants.

.IP FTW_DP 10

The object is a directory and subdirectories have been visited. (This

condition shall only occur if the FTW_DEPTH flag is included in

.IR flags .)

.IP FTW_F 10

The object is a non-directory file.

.IP FTW_NS 10

The

\fIstat\fR()

function failed on the object because of lack of appropriate

permission. The

.BR stat

buffer passed to

.IR fn

is undefined. Failure of

\fIstat\fR()

for any other reason is considered an error and

\fInftw\fR()

shall return \(mi1.

.IP FTW_SL 10

The object is a symbolic link. (This condition shall only occur if the

FTW_PHYS flag is included in

.IR flags .)

.IP FTW_SLN 10

The object is a symbolic link that does not name an existing file.

(This condition shall only occur if the FTW_PHYS flag is not included in

.IR flags .)

.RE

.IP " *" 4

The fourth argument is a pointer to an

.BR FTW

structure.

The value of

.BR base

is the offset of the object's filename in the pathname passed as the

first argument to

.IR fn .

The value of

.BR level

indicates depth relative to the root of the walk, where the root level

is 0.

.P

The results are unspecified if the application-supplied

.IR fn

function does not preserve the current working directory.

.P

The argument

.IR fd_limit

sets the maximum number of file descriptors that shall be used by

\fInftw\fR()

while traversing the file tree. At most one file descriptor shall be

used for each directory level.

.P

The

\fInftw\fR()

function need not be thread-safe.

.SH "RETURN VALUE"

The

\fInftw\fR()

function shall continue until the first of the following conditions

occurs:

.IP " *" 4

An invocation of

.IR fn

shall return a non-zero value, in which case

\fInftw\fR()

shall return that value.

.IP " *" 4

The

\fInftw\fR()

function detects an error other than

.BR [EACCES] 

(see FTW_DNR and FTW_NS above),

in which case

\fInftw\fR()

shall return \(mi1 and set

.IR errno

to indicate the error.

.IP " *" 4

The tree is exhausted, in which case

\fInftw\fR()

shall return 0.

.SH ERRORS

The

\fInftw\fR()

function shall fail if:

.TP

.BR EACCES

Search permission is denied for any component of

.IR path

or read permission is denied for

.IR path ,

or

.IR fn

returns \(mi1 and does not reset

.IR errno .

.TP

.BR ELOOP

A loop exists in symbolic links encountered during resolution of the

.IR path

argument.

.TP

.BR ENAMETOOLONG

.br

The length of a component of a pathname is longer than

{NAME_MAX}.

.TP

.BR ENOENT

A component of

.IR path

does not name an existing file or

.IR path

is an empty string.

.TP

.BR ENOTDIR

A component of

.IR path

names an existing file that is neither a directory nor a symbolic link

to a directory.

.TP

.BR EOVERFLOW

A field in the

.BR stat

structure cannot be represented correctly in the current programming

environment for one or more files found in the file hierarchy.

.P

The

\fInftw\fR()

function may fail if:

.TP

.BR ELOOP

More than

{SYMLOOP_MAX}

symbolic links were encountered during resolution of the

.IR path

argument.

.TP

.BR EMFILE

All file descriptors available to the process are currently open.

.TP

.BR ENAMETOOLONG

.br

The length of a pathname exceeds

{PATH_MAX},

or pathname resolution of a symbolic link produced an intermediate

result with a length that exceeds

{PATH_MAX}.

.TP

.BR ENFILE

Too many files are currently open in the system.

.P

In addition,

.IR errno

may be set if the function pointed to by

.IR fn

causes

.IR errno

to be set.

.LP

.IR "The following sections are informative."

.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. 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

.IR flags

argument when calling

\fInftw\fR().

.sp

.RS 4

.nf

\fB

#include <ftw.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <stdint.h>

.P

static int

display_info(const char *fpath, const struct stat *sb,

    int tflag, struct FTW *ftwbuf)

{

    printf("%-3s %2d %7jd   %-40s %d %s\en",

        (tflag == FTW_D) ?   "d"   : (tflag == FTW_DNR) ? "dnr" :

        (tflag == FTW_DP) ?  "dp"  : (tflag == FTW_F) ?

            (S_ISBLK(sb->st_mode) ? "f b" :

             S_ISCHR(sb->st_mode) ? "f c" :

             S_ISFIFO(sb->st_mode) ? "f p" :

             S_ISREG(sb->st_mode) ? "f r" :

             S_ISSOCK(sb->st_mode) ? "f s" : "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);

    return 0;           /* To tell nftw() to continue */

}

.P

int

main(int argc, char *argv[])

{

    int flags = 0;

.P

    if (argc > 2 && strchr(argv[2], 'd') != NULL)

        flags |= FTW_DEPTH;

    if (argc > 2 && strchr(argv[2], 'p') != NULL)

        flags |= FTW_PHYS;

.P

    if (nftw((argc < 2) ? "." : argv[1], display_info, 20, flags) == -1)

    {

        perror("nftw");

        exit(EXIT_FAILURE);

    }

.P

    exit(EXIT_SUCCESS);

}

.fi \fR

.P

.RE

.SH "APPLICATION USAGE"

The

\fInftw\fR()

function may allocate dynamic storage during its operation. If

\fInftw\fR()

is forcibly terminated, such as by

\fIlongjmp\fR()

or

\fIsiglongjmp\fR()

being executed by the function pointed to by

.IR fn

or an interrupt routine,

\fInftw\fR()

does not have a chance to free that storage, so it remains permanently

allocated. A safe way to handle interrupts is to store the fact that an

interrupt has occurred, and arrange to have the function pointed to by

.IR fn

return a non-zero value at its next invocation.

.SH RATIONALE

None.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

.IR "\fIfdopendir\fR\^(\|)",

.IR "\fIfstatat\fR\^(\|)",

.IR "\fIreaddir\fR\^(\|)"

.P

The Base Definitions volume of POSIX.1\(hy2008,

.IR "\fB<ftw.h>\fP"

.SH COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology

-- Portable Operating System Interface (POSIX), The Open Group Base

Specifications Issue 7, Copyright (C) 2013 by the Institute of

Electrical and Electronics Engineers, Inc and The Open Group.

(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the

event of any discrepancy between this version and the original IEEE and

The Open Group Standard, the original IEEE and The Open Group Standard

is the referee document. The original Standard can be obtained online at

http://www.unix.org/online.html .

Any typographical or formatting errors that appear

in this page are most likely

to have been introduced during the conversion of the source files to

man page format. To report such errors, see

https://www.kernel.org/doc/man-pages/reporting_bugs.html .