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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 

.TH "FTW" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"

.\" ftw 

.SH NAME

ftw \- traverse (walk) a file tree

.SH SYNOPSIS

.LP

\fB#include <ftw.h>

.br

.sp

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

char *,

.br

\ \ \ \ \ \  const struct stat *\fP\fIptr\fP\fB, int\fP \fIflag\fP\fB),

int\fP

\fIndirs\fP\fB); \fP

\fB

.br

\fP

.SH DESCRIPTION

.LP

The \fIftw\fP() function shall recursively descend the directory hierarchy

rooted in \fIpath\fP. For each object in the

hierarchy, \fIftw\fP() shall call the function pointed to by \fIfn\fP,

passing it a pointer to a null-terminated character string

containing the name of the object, a pointer to a \fBstat\fP structure

containing information about the object, and an integer.

Possible values of the integer, defined in the \fI<ftw.h>\fP header,

are:

.TP 7

FTW_D

For a directory.

.TP 7

FTW_DNR

For a directory that cannot be read.

.TP 7

FTW_F

For a file.

.TP 7

FTW_SL

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

.TP 7

FTW_NS

For an object other than a symbolic link on which \fIstat\fP() could

not successfully be

executed. If the object is a symbolic link and \fIstat\fP() failed,

it is unspecified whether

\fIftw\fP() passes FTW_SL or FTW_NS to the user-supplied function.

.sp

.LP

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

be processed. If the integer is FTW_NS, the \fBstat\fP

structure contains undefined values. An example of an object that

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

\fIfn\fP would be a file in a directory with read but without execute

(search) permission.

.LP

The \fIftw\fP() function shall visit a directory before visiting any

of its descendants.

.LP

The \fIftw\fP() function shall use at most one file descriptor for

each level in the tree.

.LP

The argument \fIndirs\fP should be in the range [1, {OPEN_MAX}].

.LP

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

an invocation of \fIfn\fP returns a non-zero value, or

some error, other than [EACCES], is detected within \fIftw\fP().

.LP

The \fIndirs\fP argument shall specify the maximum number of directory

streams or file descriptors or both available for use by

\fIftw\fP() while traversing the tree. When \fIftw\fP() returns it

shall close any directory streams and file descriptors it uses

not counting any opened by the application-supplied \fIfn\fP function.

.LP

The results are unspecified if the application-supplied \fIfn\fP function

does not preserve the current working directory.

.LP

The \fIftw\fP() function need not be reentrant. A function that is

not required to be reentrant is not required to be

thread-safe.

.SH RETURN VALUE

.LP

If the tree is exhausted, \fIftw\fP() shall return 0. If the function

pointed to by \fIfn\fP returns a non-zero value,

\fIftw\fP() shall stop its tree traversal and return whatever value

was returned by the function pointed to by \fIfn\fP. If

\fIftw\fP() detects an error, it shall return -1 and set \fIerrno\fP

to indicate the error.

.LP

If \fIftw\fP() encounters an error other than [EACCES] (see FTW_DNR

and FTW_NS above), it shall return -1 and set \fIerrno\fP

to indicate the error. The external variable \fIerrno\fP may contain

any error value that is possible when a directory is opened

or when one of the \fIstat\fP functions is executed on a directory

or file.

.SH ERRORS

.LP

The \fIftw\fP() function shall fail if:

.TP 7

.B EACCES

Search permission is denied for any component of \fIpath\fP or read

permission is denied for \fIpath\fP.

.TP 7

.B ELOOP

A loop exists in symbolic links encountered during resolution of the

\fIpath\fP argument.

.TP 7

.B ENAMETOOLONG

The length of the \fIpath\fP argument exceeds {PATH_MAX} or a pathname

component is longer than {NAME_MAX}.

.TP 7

.B ENOENT

A component of \fIpath\fP does not name an existing file or \fIpath\fP

is an empty string.

.TP 7

.B ENOTDIR

A component of \fIpath\fP is not a directory.

.TP 7

.B EOVERFLOW

A field in the \fBstat\fP structure cannot be represented correctly

in the current programming environment for one or more

files found in the file hierarchy.

.sp

.LP

The \fIftw\fP() function may fail if:

.TP 7

.B EINVAL

The value of the \fIndirs\fP argument is invalid.

.TP 7

.B ELOOP

More than {SYMLOOP_MAX} symbolic links were encountered during resolution

of the \fIpath\fP argument.

.TP 7

.B ENAMETOOLONG

Pathname resolution of a symbolic link produced an intermediate result

whose length exceeds {PATH_MAX}.

.sp

.LP

In addition, if the function pointed to by \fIfn\fP encounters system

errors, \fIerrno\fP may be set accordingly.

.LP

\fIThe following sections are informative.\fP

.SH EXAMPLES

.SS Walking a Directory Structure

.LP

The following example walks the current directory structure, calling

the \fIfn\fP function for every directory entry, using at

most 10 file descriptors:

.sp

.RS

.nf

\fB#include <ftw.h>

\&...

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

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

}

\fP

.fi

.RE

.SH APPLICATION USAGE

.LP

The \fIftw\fP() function may allocate dynamic storage during its operation.

If \fIftw\fP() is forcibly terminated, such as by

\fIlongjmp\fP() or \fIsiglongjmp\fP() being

executed by the function pointed to by \fIfn\fP or an interrupt routine,

\fIftw\fP() 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 \fIfn\fP return a non-zero

value at its next invocation.

.SH RATIONALE

.LP

None.

.SH FUTURE DIRECTIONS

.LP

None.

.SH SEE ALSO

.LP

\fIlongjmp\fP() , \fIlstat\fP() , \fImalloc\fP() , \fInftw\fP() ,

\fIopendir\fP() , \fIsiglongjmp\fP() , \fIstat\fP() , the Base Definitions

volume of

IEEE\ Std\ 1003.1-2001, \fI<ftw.h>\fP, \fI<sys/stat.h>\fP

.SH COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology

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

Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of

Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .