FreeBSD manual
download PDF document: nftw.3.pdf
FTW(3) FreeBSD Library Functions Manual FTW(3)
NAME
ftw, nftw - traverse (walk) a file tree
SYNOPSIS
#include <ftw.h>
int
ftw(const char *path, int (*fn)(const char *, const struct stat *, int),
int maxfds);
int
nftw(const char *path,
int (*fn)(const char *, const struct stat *, int, struct FTW *),
int maxfds, int flags);
DESCRIPTION
The ftw() and nftw() functions traverse (walk) the directory hierarchy
rooted in path. For each object in the hierarchy, these functions call
the function pointed to by fn. The ftw() function passes this function a
pointer to a NUL-terminated string containing the name of the object, a
pointer to a stat structure corresponding to the object, and an integer
flag. The nftw() function passes the aforementioned arguments plus a
pointer to a FTW structure as defined by <ftw.h> (shown below):
struct FTW {
int base; /* offset of basename into pathname */
int level; /* directory depth relative to starting point */
};
Possible values for the flag passed to fn are:
FTW_F A regular file.
FTW_D A directory being visited in pre-order.
FTW_DNR A directory which cannot be read. The directory will not be
descended into.
FTW_DP A directory being visited in post-order (nftw() only).
FTW_NS A file for which no stat(2) information was available. The
contents of the stat structure are undefined.
FTW_SL A symbolic link.
FTW_SLN A symbolic link with a non-existent target (nftw() only).
The ftw() function traverses the tree in pre-order. That is, it
processes the directory before the directory's contents.
The maxfds argument specifies the maximum number of file descriptors to
keep open while traversing the tree. It has no effect in this
implementation.
The nftw() function has an additional flags argument with the following
possible values:
FTW_CHDIR Change to a directory before reading it. By default, nftw()
will change its starting directory. The current working
directory will be restored to its original value before nftw()
returns.
RETURN VALUES
If the tree was traversed successfully, the ftw() and nftw() functions
return 0. If the function pointed to by fn returns a non-zero value,
ftw() and nftw() will stop processing the tree and return the value from
fn. Both functions return -1 if an error is detected.
EXAMPLES
Following there is an example that shows how nftw can be used. It
traverses the file tree starting at the directory pointed by the only
program argument and shows the complete path and a brief indicator about
the file type.
#include <ftw.h>
#include <stdio.h>
#include <sysexits.h>
int
nftw_callback(const char *path, const struct stat *sb, int typeflag, struct FTW *ftw)
{
char type;
switch(typeflag) {
case FTW_F:
type = 'F';
break;
case FTW_D:
type = 'D';
break;
case FTW_DNR:
type = '-';
break;
case FTW_DP:
type = 'd';
break;
case FTW_NS:
type = 'X';
break;
case FTW_SL:
type = 'S';
break;
case FTW_SLN:
type = 's';
break;
default:
type = '?';
break;
}
printf("[%c] %s\n", type, path);
return (0);
}
} else
return (nftw(argv[1], nftw_callback, /* UNUSED */ 1, 0));
}
ERRORS
The ftw() and nftw() functions may fail and set errno for any of the
errors specified for the library functions close(2), open(2), stat(2),
malloc(3), opendir(3) and readdir(3). If the FTW_CHDIR flag is set, the
nftw() function may fail and set errno for any of the errors specified
for chdir(2). In addition, either function may fail and set errno as
follows:
[EINVAL] The maxfds argument is less than 1.
SEE ALSO
chdir(2), close(2), open(2), stat(2), fts(3), malloc(3), opendir(3),
readdir(3)
STANDARDS
The ftw() and nftw() functions conform to IEEE Std 1003.1-2001
("POSIX.1").
HISTORY
These functions first appeared in AT&T System V Release 3 UNIX. Their
first FreeBSD appearance was in FreeBSD 5.3.
BUGS
The maxfds argument is currently ignored.
FreeBSD 14.0-RELEASE-p11 March 12, 2020 FreeBSD 14.0-RELEASE-p11