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.TH FTW "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

ftw

\(em traverse (walk) a file tree

.SH SYNOPSIS

.LP

.nf

#include <ftw.h>

.P

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

    const struct stat *\fIptr\fP, int \fIflag\fP), int \fIndirs\fP);

.fi

.SH DESCRIPTION

The

\fIftw\fR()

function shall recursively descend the directory hierarchy rooted in

.IR path .

For each object in the hierarchy,

\fIftw\fR()

shall call the function pointed to by

.IR fn ,

passing it a pointer to a null-terminated character string containing

the name of the object, a pointer to a

.BR stat

structure containing information about the object, filled in as if

\fIstat\fR()

or

\fIlstat\fR()

had been called to retrieve the information. Possible values of the

integer, defined in the

.IR <ftw.h> 

header, are:

.IP FTW_D 10

For a directory.

.IP FTW_DNR 10

For a directory that cannot be read.

.IP FTW_F 10

For a non-directory file.

.IP FTW_SL 10

For a symbolic link (but see also FTW_NS below).

.IP FTW_NS 10

For an object other than a symbolic link on which

\fIstat\fR()

could not successfully be executed. If the object is a symbolic link

and

\fIstat\fR()

failed, it is unspecified whether

\fIftw\fR()

passes FTW_SL or FTW_NS to the user-supplied function.

.P

If the integer is FTW_DNR, descendants of that directory shall not be

processed. If the integer is FTW_NS, the

.BR stat

structure contains undefined values. An example of an object that

would cause FTW_NS to be passed to the function pointed to by

.IR fn

would be a file in a directory with read but without execute (search)

permission.

.P

The

\fIftw\fR()

function shall visit a directory before visiting any of its

descendants.

.P

The

\fIftw\fR()

function shall use at most one file descriptor for each level in

the tree.

.P

The argument

.IR ndirs

should be in the range [1,\c

{OPEN_MAX}].

.P

The tree traversal shall continue until either the tree is exhausted,

an invocation of

.IR fn

returns a non-zero value, or some error, other than

.BR [EACCES] ,

is detected within

\fIftw\fR().

.P

The

.IR ndirs

argument shall specify the maximum number of directory streams or file

descriptors or both available for use by

\fIftw\fR()

while traversing the tree. When

\fIftw\fR()

returns it shall close any directory streams and file descriptors it

uses not counting any opened by the application-supplied

.IR fn

function.

.P

The results are unspecified if the application-supplied

.IR fn

function does not preserve the current working directory.

.P

The

\fIftw\fR()

function need not be thread-safe.

.SH "RETURN VALUE"

If the tree is exhausted,

\fIftw\fR()

shall return 0. If the function pointed to by

.IR fn

returns a non-zero value,

\fIftw\fR()

shall stop its tree traversal and return whatever value was returned

by the function pointed to by

.IR fn .

If

\fIftw\fR()

detects an error, it shall return \(mi1 and set

.IR errno

to indicate the error.

.P

If

\fIftw\fR()

encounters an error other than

.BR [EACCES] 

(see FTW_DNR and FTW_NS above), it shall return \(mi1 and set

.IR errno

to indicate the error. The external variable

.IR errno

may contain any error value that is possible when a directory is opened

or when one of the

.IR stat

functions is executed on a directory or file.

.SH ERRORS

The

\fIftw\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 .

.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

\fIftw\fR()

function may fail if:

.TP

.BR EINVAL

The value of the

.IR ndirs

argument is invalid.

.TP

.BR ELOOP

More than

{SYMLOOP_MAX}

symbolic links were encountered during resolution of the

.IR path

argument.

.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}.

.P

In addition, if the function pointed to by

.IR fn

encounters system errors,

.IR errno

may be set accordingly.

.LP

.IR "The following sections are informative."

.SH EXAMPLES

.SS "Walking a Directory Structure"

.P

The following example walks the current directory structure, calling

the

.IR fn

function for every directory entry, using at most 10 file descriptors:

.sp

.RS 4

.nf

\fB

#include <ftw.h>

\&...

if (ftw(".", fn, 10) != 0) {

    perror("ftw"); exit(2);

}

.fi \fR

.P

.RE

.SH "APPLICATION USAGE"

The

\fIftw\fR()

function may allocate dynamic storage during its operation. If

\fIftw\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,

\fIftw\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.

.P

Applications should use the

\fInftw\fR()

function instead of the obsolescent

\fIftw\fR()

function.

.SH RATIONALE

None.

.SH "FUTURE DIRECTIONS"

The

\fIftw\fR()

function may be removed in a future version.

.SH "SEE ALSO"

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

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

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

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

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

.P

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

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

.IR "\fB<sys_stat.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 .