fts_open(), fts_read(), fts_children(), fts_set(), fts_close() - traverse a file hierarchy
#include <sys/types.h>
#include <sys/stat.h>
#include <fts.h>
FTS * fts_open (char *const *path_argv, int options, int
*compar(const FTSENT **, const FTSENT **))
FTSENT * fts_read (FTS *ftsp)
FTSENT * fts_children (FTS *ftsp, int options)
int fts_set (FTS ftsp, FTSENT *f, int options)
int fts_close (FTS *ftsp)
The fts(3) functions are provided for traversing file hierarchies. A simple overview is that the fts_open(3) function returns a handle on a file hierarchy, which is then supplied to the other fts(3) functions. The function fts_read(3) returns a pointer to a structure describing one of the files in the file hierarchy. The function fts_children(3) returns a pointer to a linked list of structures, each of which describes one of the files contained in a directory in the hierarchy. In general, directories are visited two distinguishable times; in pre-order (before any of their descendants are visited) and in post-order (after all of their descendants have been visited). Files are visited once. It is possible to walk the hierarchy logically or physically, order the walk of the hierarchy or prune and/or re-visit portions of the hierarchy.
Two structures are defined (and typedef'd) in the include file <fts.h>. The first is FTS, the structure that represents the file hierarchy itself. The second is FTSENT, the structure that represents a file in the file hierarchy. Normally, an FTSENT structure is returned for every file in the file hierarchy. In this manual page, file and FTSENT structure are generally interchangeable. The FTSENT structure contains at least the following fields, which are described in greater detail below:
typedef struct _ftsent {
u_short fts_info; /* flags for FTSENT structure */
char * fts_accpath; /* access path */
char * fts_path; /* root path */
short fts_pathlen; /* strlen(fts_path) */
char * fts_name; /* file name */
short fts_namelen; /* strlen(fts_name) */
short fts_level; /* depth (-1 to N) */
int fts_errno; /* file errno */
long fts_number; /* local numeric value */
void * fts_pointer; /* local address value */
struct ftsent * fts_parent; /* parent directory */
struct ftsent * fts_link; /* next file structure */
struct ftsent * fts_cycle; /* cycle structure */
struct stat * fts_statp; /* stat() information */
} FTSENT;
These fields are defined as follows:
. or .. which was not
specified as a file name to fts_open(3) (see FTS_SEEDOT).A single buffer is used for all of the paths of all of the files in the file hierarchy. Therefore, the fts_path and fts_accpath fields are guaranteed to be NULL-terminated only for the file most recently returned by fts_read(3). To use these fields to reference any files represented by other FTSENT structures will require that the path buffer be modified using the information contained in that FTSENT structure's fts_pathlen field. Any such modifications should be undone before further calls to fts_read(3) are attempted. The fts_name field is always NULL -terminated.
The fts_open(3) function takes a pointer to an array of character pointers naming one or more paths which make up a logical file hierarchy to be traversed. The array must be terminated by a NULL pointer.
There are a number of options, at least one of which (either FTS_LOGICAL or FTS_PHYSICAL) must be specified. The options are selected by OR'ing the following values:
. or
.. encountered in the file hierarchy are ignored. This
option causes the fts(3) routines to return FTSENT
structures for them.The argument compar() specifies a user-defined function which may be used to order the traversal of the hierarchy. It takes two pointers to pointers to FTSENT structures as arguments and should return a negative value, zero, or a positive value to indicate if the file referenced by its first argument comes before, in any order with respect to, or after, the file referenced by its second argument. The fts_accpath, fts_path and fts_pathlen fields of the FTSENT structures may never be used in this comparison. If the fts_info field is set to FTS_NS or FTS_NSOK, the fts_statp field may not either. If the compar() argument is NULL, the directory traversal order is in the order listed in path_argv for the root paths, and in the order listed in the directory for everything else.
The fts_read(3) function returns a pointer to an FTSENT structure describing a file in the hierarchy. Directories (that are readable and do not cause cycles) are visited at least twice, once in pre-order and once in post-order. All other files are visited at least once. (Hard links between directories that do not cause cycles or symbolic links to symbolic links may cause files to be visited more than once, or directories more than twice.)
If all the members of the hierarchy have been returned, fts_read(3) returns NULL and sets the external variable errno to 0. If an error unrelated to a file in the hierarchy occurs, fts_read(3) returns NULL and sets errno appropriately. If an error related to a returned file occurs, a pointer to an FTSENT structure is returned, and errno may or may not have been set (see fts_info).
The FTSENT structures returned by fts_read(3) may be overwritten after a call to fts_close(3) on the same file hierarchy stream, or, after a call to fts_read(3) on the same file hierarchy stream unless they represent a file of type directory, in which case they will not be overwritten until after a call to fts_read(3) after the FTSENT structure has been returned by the function fts_read(3) in post-order.
The fts_children(3) function returns a pointer to an FTSENT structure describing the first entry in a NULL-terminated linked list of the files in the directory represented by the FTSENT structure most recently returned by fts_read(3). The list is linked through the fts_link field of the FTSENT structure, and is ordered by the user-specified comparison function, if any. Repeated calls to fts_children(3) will recreate this linked list.
As a special case, if fts_read(3) has not yet been called for a hierarchy, fts_children(3) will return a pointer to the files in the logical directory specified to fts_open(3), i.e. the arguments specified to fts_open(3). Otherwise, if the FTSENT structure most recently returned by fts_read(3) is not a directory being visited in pre-order, or the directory does not contain any files, fts_children(3) returns NULL and sets errno to zero. If an error occurs, fts_children(3) returns NULL and sets errno appropriately.
The FTSENT structures returned by fts_children(3) may be overwritten after a call to fts_children(3), fts_close(3) or fts_read(3) on the same file hierarchy stream.
Option may be set to the following value:
The function fts_set(3) allows the user application to determine further processing for the file f of the stream ftsp. The fts_set(3) function returns 0 on success, and -1 if an error occurs. Option must be set to one of the following values:
The fts_close(3) function closes a file hierarchy stream ftsp and restores the current directory to the directory from which fts_open(3) was called to open ftsp. The fts_close(3) function returns 0 on success, and -1 if an error occurs.
The function fts_open(3) may fail and set errno for any of the errors specified for the library functions open(2) and malloc(3).
The function fts_close(3) may fail and set errno for any of the errors specified for the library functions chdir(2) and close(2).
The functions fts_read(3) and fts_children(3) may fail and set errno for any of the errors specified for the library functions chdir(2), malloc(3), opendir(3), readdir(2) and stat(2).
In addition, fts_children(3), fts_open(3) and fts_set(3) may fail and set errno as follows:
find(1)
chdir(2)
stat(2)
qsort(3)