Standard C Library Functions ftw(3C)
NAME
ftw, nftw - walk a file tree
SYNOPSIS
#include
int ftw(const char *path, int (*fn) (const char *, const struct stat *, int), int depth);int nftw(const char *path, int (*fn) (const char *,
const struct stat *, int, struct FTW *), int depth, int flags);DESCRIPTION
The ftw() function recursively descends the directory hierarchy rooted in path. For each object in the hierarchy,ftw() calls the user-defined function fn, passing it a
pointer to a null-terminated character string containing the
name of the object, a pointer to a stat structure (see stat(2)) containing information about the object, and an integer. Possible values of the integer, defined in theheader, are: FTW_F The object is a file.
FTW_D The object is a directory.
FTW_DNR The object is a directory that cannot be read.
Descendants of the directory are not processed.FTW_NS The stat() function failed on the object because
of lack of appropriate permission or the objectis a symbolic link that points to a non-existent
file. The stat buffer passed to fn is undefined. The ftw() function visits a directory before visiting any of its descendants. The tree traversal continues until the tree is exhausted, aninvocation of fn returns a non-zero value, or some error is
detected within ftw() (such as an I/O error). If the tree is
exhausted, ftw() returns 0. If fn returns a non-zero value,
ftw() stops its tree traversal and returns whatever value was returned by fn.SunOS 5.11 Last change: 30 Jan 2007 1
Standard C Library Functions ftw(3C)The nftw() function is similar to ftw() except that it
takes the additional argument flags, which is a bitwise-
inclusive OR of zero or more of the following flags:FTW_CHDIR If set, nftw() changes the current working
directory to each directory as it reports filesin that directory. If clear, nftw() does not
change the current working directory.FTW_DEPTH If set, nftw() reports all files in a directory
before reporting the directory itself. Ifclear, nftw() reports any directory before
reporting the files in that directory.FTW_MOUNT If set, nftw() reports only files in the same
file system as path. If clear, nftw() reports
all files encountered during the walk.FTW_PHYS If set, nftw() performs a physical walk and
does not follow symbolic links.If FTW_PHYS is clear and FTW_DEPTH is set, nftw() follows
links instead of reporting them, but does not report anydirectory that would be a descendant of itself. If FTW_PHYS
is clear and FTW_DEPTH is clear, nftw() follows links
instead of reporting them, but does not report the contents of any directory that would be a descendant of itself.At each file it encounters, nftw() calls the user-supplied
function fn with four arguments: o The first argument is the pathname of the object. o The second argument is a pointer to the stat buffer containing information on the object. o The third argument is an integer giving additional information. Its value is one of the following:FTW_F The object is a file.
FTW_D The object is a directory.
SunOS 5.11 Last change: 30 Jan 2007 2
Standard C Library Functions ftw(3C)FTW_DP The object is a directory and subdirec-
tories have been visited. (This condi-
tion only occurs if the FTW_DEPTH flag
is included in flags.)FTW_SL The object is a symbolic link. (This
condition only occurs if the FTW_PHYS
flag is included in flags.)FTW_SLN The object is a symbolic link that
points to a non-existent file. (This
condition only occurs if the FTW_PHYS
flag is not included in flags.)FTW_DNR The object is a directory that cannot be
read. The user-defined function fn will
not be called for any of its descen-
dants.FTW_NS The stat() function failed on the object
because of lack of appropriate permis-
sion. The stat buffer passed to fn is undefined. Failure of stat() for any other reason is considered an error andnftw() returns -1.
o The fourth argument is a pointer to an FTW struc-
ture that contains the following members: int base; int level; The base member is the offset of the object'sfilename in the pathname passed as the first argu-
ment to fn(). The value of level indicates the depth relative to the root of the walk, where the root level is 0.The results are unspecified if the application-
supplied fn() function does not preserve the current working directory.Both ftw() and nftw() use one file descriptor for each level
in the tree. The depth argument limits the number of file descriptors used. If depth is zero or negative, the effectSunOS 5.11 Last change: 30 Jan 2007 3
Standard C Library Functions ftw(3C) is the same as if it were 1. It must not be greater than the number of file descriptors currently available for use. The ftw() function runs faster if depth is at least as large asthe number of levels in the tree. Both ftw() and nftw() are
able to descend to arbitrary depths in a file hierarchy and do not fail due to path length limitations unless either the length of the path name pointed to by the path argumentexceeds {PATH_MAX} requirements, or for ftw(), the specified
depth is less than 2, or for nftw(), the specified depth is
less than 2 and FTW_CHDIR is not set. When ftw() and nftw()
return, they close any file descriptors they have opened; they do not close any file descriptors that might have been opened by fn.RETURN VALUES
If the tree is exhausted, ftw() and nftw() return 0. If the
function pointed to by fn returns a non-zero value, ftw()
and nftw() stop their tree traversal and return whatever
value was returned by the function pointed to by fn. Ifftw() and nftw() detect an error, they return -1 and set
errno to indicate the error.If ftw() and nftw() encounter an error other than EACCES
(see FTW_DNR and FTW_NS above), they return -1 and set
errno to indicate the error. The external variable errno can 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.ERRORS
The ftw() and nftw() functions will fail if:
ELOOP A loop exists in symbolic links encountered during resolution of the path argumentENAMETOOLONG The length of the path name pointed to by
the path argument exceeds {PATH_MAX}, or a
path name component is longer than{NAME_MAX}.
ENOENT A component of path does not name an exist-
ing 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 currentSunOS 5.11 Last change: 30 Jan 2007 4
Standard C Library Functions ftw(3C) programming environment for one or more files found in the file hierarchy. The ftw() function will fail if:EACCES Search permission is denied for any com-
ponent of path or read permission is denied for path.ENAMETOOLONG The ftw() function has descended to a path
that exceeds {PATH_MAX} and the depth argu-
ment specified by the application is lessthan 2 and FTW_CHDIR is not set.
The nftw() function will fail if:
EACCES Search permission is denied for any component of path or read permission is denied for path, orfn() returns -1 and does not reset errno.
The nftw() and ftw() functions may fail if:
ELOOP Too many symbolic links were encountered during resolution of the path argument.ENAMETOOLONG Pathname resolution of a symbolic link in
the path name pointed to by the path argu-
ment produced an intermediate result whoselength exceeds {PATH_MAX}.
The ftw() function may fail if: EINVAL The value of the depth argument is invalid.The nftw() function may fail if:
EMFILE There are {OPEN_MAX} file descriptors currently
open in the calling process.SunOS 5.11 Last change: 30 Jan 2007 5
Standard C Library Functions ftw(3C) ENFILE Too many files are currently open in the system. If the function pointed to by fn encounters system errors, errno may be set accordingly.EXAMPLES
Example 1 Walk a directory structure using ftw(). The following example walks the current directory structure, calling the fn() function for every directory entry, using at most 10 file descriptors:#include
... if (ftw(".", fn, 10) != 0) { perror("ftw"); exit(2); }Example 2 Walk a directory structure using nftw().
The following example walks the /tmp directory and its sub-
directories, calling the nftw() function for every directory
entry, to a maximum of 5 levels deep.#include
...int nftwfunc(const char *, const struct stat *, int, struct FTW *);
int nftwfunc(const char *filename, const struct stat *statptr,
int fileflags, struct FTW *pfwt) { return 0; } ... char *startpath = "/tmp"; int depth = 5;int flags = FTW_CHDIR | FTW_DEPTH | FTW_MOUNT;
int ret;ret = nftw(startpath, nftwfunc, depth, flags);
USAGE
Because ftw() and nftw() are recursive, they can terminate
with a memory fault when applied by a thread with a small stack to very deep file structures.SunOS 5.11 Last change: 30 Jan 2007 6
Standard C Library Functions ftw(3C)The ftw() and nftw() functions allocate resources (memory,
file descriptors) during their operation. If ftw() they are forcibly terminated, such as by longjmp(3C) being executed by fn or an interrupt routine, they will not have a chanceto free those resources, so they remain permanently allo-
cated. A safe way to handle interrupts is to store the fact that an interrupt has occurred and arrange to have fn returna non-zero value at its next invocation.
The ftw() and nftw() functions have transitional interfaces
for 64-bit file offsets. See lf64(5).
The ftw() function is safe in multithreaded applications.The nftw() function is safe in multithreaded applications
when the FTW_CHDIR flag is not set.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Interface Stability | Committed ||_____________________________|_____________________________|
| MT-Level | MT-Safe with exceptions |
|_____________________________|_____________________________|
| Standard | See standards(5). ||_____________________________|_____________________________|
SEE ALSO
stat(2), longjmp(3C), attributes(5), lf64(5), standards(5)SunOS 5.11 Last change: 30 Jan 2007 7