.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "FTW" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" ftw 
.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 \- 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 .