Originální popis anglicky:
ftw - traverse (walk) a file tree
Návod, kniha: POSIX Programmer's Manual
#include <ftw.h>
int ftw(const char *
path, int
(*fn )(const char *,
const struct stat *
ptr , int flag),
int ndirs);
The
ftw() function shall recursively descend the directory hierarchy
rooted in
path. For each object in the hierarchy,
ftw() shall
call the function pointed to by
fn, passing it a pointer to a
null-terminated character string containing the name of the object, a pointer
to a
stat structure containing information about the object, and an
integer. Possible values of the integer, defined in the
<ftw.h>
header, are:
- FTW_D
- For a directory.
- FTW_DNR
- For a directory that cannot be read.
- FTW_F
- For a file.
- FTW_SL
- For a symbolic link (but see also FTW_NS below).
- FTW_NS
- For an object other than a symbolic link on which
stat() could not successfully be executed. If the object is a
symbolic link and stat() failed, it is unspecified whether
ftw() passes FTW_SL or FTW_NS to the user-supplied function.
If the integer is FTW_DNR, descendants of that directory shall not be processed.
If the integer is FTW_NS, the
stat structure contains undefined values.
An example of an object that would cause FTW_NS to be passed to the function
pointed to by
fn would be a file in a directory with read but without
execute (search) permission.
The
ftw() function shall visit a directory before visiting any of its
descendants.
The
ftw() function shall use at most one file descriptor for each level
in the tree.
The argument
ndirs should be in the range [1, {OPEN_MAX}].
The tree traversal shall continue until either the tree is exhausted, an
invocation of
fn returns a non-zero value, or some error, other than
[EACCES], is detected within
ftw().
The
ndirs argument shall specify the maximum number of directory streams
or file descriptors or both available for use by
ftw() while traversing
the tree. When
ftw() returns it shall close any directory streams and
file descriptors it uses not counting any opened by the application-supplied
fn function.
The results are unspecified if the application-supplied
fn function does
not preserve the current working directory.
The
ftw() function need not be reentrant. A function that is not required
to be reentrant is not required to be thread-safe.
If the tree is exhausted,
ftw() shall return 0. If the function pointed
to by
fn returns a non-zero value,
ftw() shall stop its tree
traversal and return whatever value was returned by the function pointed to by
fn. If
ftw() detects an error, it shall return -1 and set
errno to indicate the error.
If
ftw() encounters an error other than [EACCES] (see FTW_DNR and FTW_NS
above), it shall return -1 and set
errno to indicate the error. The
external variable
errno may contain any error value that is possible
when a directory is opened or when one of the
stat functions is
executed on a directory or file.
The
ftw() function shall fail if:
- EACCES
- Search permission is denied for any component of
path or read permission is denied for path.
- ELOOP
- A loop exists in symbolic links encountered during
resolution of the path argument.
- ENAMETOOLONG
- The length of the path argument exceeds {PATH_MAX}
or a pathname component is longer than {NAME_MAX}.
- ENOENT
- A component of path does not name an existing file
or path is an empty string.
- ENOTDIR
- A component of path is not a directory.
- EOVERFLOW
- A field in the stat structure cannot be represented
correctly in the current programming environment for one or more files
found in the file hierarchy.
The
ftw() function may fail if:
- EINVAL
- The value of the ndirs argument is invalid.
- ELOOP
- More than {SYMLOOP_MAX} symbolic links were encountered
during resolution of the path argument.
- ENAMETOOLONG
- Pathname resolution of a symbolic link produced an
intermediate result whose length exceeds {PATH_MAX}.
In addition, if the function pointed to by
fn encounters system errors,
errno may be set accordingly.
The following sections are informative.
The following example walks the current directory structure, calling the
fn function for every directory entry, using at most 10 file
descriptors:
#include <ftw.h>
...
if (ftw(".", fn, 10) != 0) {
perror("ftw"); exit(2);
}
The
ftw() function may allocate dynamic storage during its operation. If
ftw() is forcibly terminated, such as by
longjmp() or
siglongjmp() being executed by the function pointed to by
fn or
an interrupt routine,
ftw() 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
fn return a non-zero value at its next
invocation.
None.
None.
longjmp() ,
lstat() ,
malloc() ,
nftw() ,
opendir() ,
siglongjmp() ,
stat() , the Base Definitions
volume of IEEE Std 1003.1-2001,
<ftw.h>,
<sys/stat.h>
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
.
