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ftw(3C)HP-UX 11i Version 3: February 2007
ftw(), nftw() — walk a file tree executing a function
#include <ftw.h> int ftw (const char *path, int (*fn)(const char *obj_path, const struct stat *obj_stat, int obj_flags), int depth); int nftw (const char *path, int (*fn)(const char *obj_path, const struct stat *obj_stat, int obj_flags, struct FTW obj_FTW), int depth, int flags);
int nftw (const char *path, int (*fn)(const char *obj_path, const struct stat *obj_stat, int obj_flags, struct *FTW obj_FTW), int depth, int flags);
The ftw() function recursively descends the directory hierarchy rooted in path. For each object in the hierarchy, ftw() calls 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 (see lstat() in stat(2)), and an integer, obj_flags. The possible values of obj_flags, defined in the <ftw.h> header file, are:
Tree traversal continues until the tree is exhausted, an invocation of fn returns a nonzero value, or an error is detected within ftw(), such as an I/O error. If the tree is exhausted, ftw() returns zero. If fn returns a nonzero value, ftw() stops its tree traversal and returns the same value as returned by fn. If ftw() detects an error, it returns -1 and sets the error type in errno (see errno(2)).
ftw() reports a directory before reporting any of its descendants.
ftw() and nftw() use one file descriptor for each level in the tree. The depth argument limits the number of file descriptors that can be used. If depth is 0 or negative, the effect is the same as if it were 1. depth must not be greater than the number of file descriptors currently available for use. For best performance, depth should be at least as large as the number of levels in the tree.
nftw() is similar to ftw() except that it takes the additional argument flags, and does not report or enter a directory which has already been visited during the walk. The flags field is the inclusive OR of the following values, as defined in the <ftw.h> header file:
nftw() calls fn with four arguments for each object reported. The first argument is the path name of the file, directory, or symbolic link. The second argument is a pointer to a stat structure (see lstat(2)) containing information about the object. The third argument is an integer giving additional information as follows:
The fourth argument is different for the default environment and the UNIX95 environment. For the default environment, the fourth argument is a structure FTW. For the UNIX95 environment, the fourth argument is a pointer to a structure FTW (ie: *FTW). FTW contains the following members:
int base; int level;
The value of base is the offset from the first character in the path name to where the base name of the object starts; this path name is passed as the first argument to fn. The value of level indicates depth relative to the start of the walk, where the start level has a value of zero.
ftw() can execute concurrently in separate threads. nftw() and nftw2() are serialized if the path argument is relative (i.e., does not start with '/'), or the FTW_CHDIR flag is set. For best concurrency, call nftw() with an absolute starting path and do not set FTW_CHDIR.
To use the UNIX95 prototype, the UNIX95 environment must be defined. This is done by defining the UNIX95 environment variable, passing the _XOPEN_SOURCE_EXTENDED flag as a compiler option, and adding /usr/xpg4/bin to your path. This can be done as follows:
nftw2() is to be obsoleted at a future date.
If ftw() or nftw() fails, it sets errno (see errno(2)) to one of the following values:
In addition, if the function pointed to by fn encounters system errors, errno may be set accordingly.
For 32-bit applications, st_ino will be truncated to its least significant 32-bits for filesystems that use 64-bit values. Note that this will even occur for ftw64() calls because st_ino is defined as an unsigned long.
For 32-bit applications accessing large file systems, use ftw64() or nftw64() instead in order to avoid overflow of the stat structure.
nftw() contains some recursion and it is possible for it to terminate with a memory fault when applied to file trees which contain a large number of directories, or a large number of files when FTW_PHYS is clear and the UNIX95 environment is defined.
nftw() uses malloc() to allocate dynamic storage during operation (see malloc(3C)). If it is forcibly terminated (such as if longjmp() is executed by fn or an interrupt routine), the calling function will not have a chance to free that storage, causing it to remain allocated until the process terminates. A safe way to handle interrupts is to store the fact that an interrupt has occurred, and arrange to have fn return a nonzero value at its next invocation.
If the starting path is in a loopback file system (LOFS) and FTW_MOUNT is set (to stay within the LOFS), but FTW_PHYS is clear (symbolic and hard links are followed), nftw() cannot determine whether a link referencing a file on the same _device_ is really within the LOFS. It is possible with this specific combination of factors to have some files reported to fn which should not be.