fts - Man Page

Standard C library (libc, -lc)

#include <sys/types.h>
#include <sys/stat.h>
#include <fts.h>

FTS *fts_open(char *const *path_argv, int options,
              int (*_Nullable compar)(const FTSENT **, const FTSENT **));

FTSENT *fts_read(FTS *ftsp);

FTSENT *fts_children(FTS *ftsp, int instr);

int fts_set(FTS *ftsp, FTSENT *f, int instr);

int fts_close(FTS *ftsp);

The fts functions are provided for traversing file hierarchies. A simple overview is that the fts_open() function returns a "handle" (of type FTS *) that refers to a file hierarchy "stream". This handle is then supplied to the other fts functions. The function fts_read() returns a pointer to a structure describing one of the files in the file hierarchy. The function fts_children() 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 preorder (before any of their descendants are visited) and in postorder (after all of their descendants have been visited). Files are visited once. It is possible to walk the hierarchy "logically" (visiting the files that symbolic links point to) or physically (visiting the symbolic links themselves), order the walk of the hierarchy or prune and/or revisit portions of the hierarchy.

Two structures (and associated types) are defined in the include file <fts.h>. The first type is FTS, the structure that represents the file hierarchy itself. The second type 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 fields describing a file. The structure contains at least the following fields (there are additional fields that should be considered private to the implementation):

typedef struct _ftsent {
    unsigned short  fts_info;     /* flags for FTSENT structure */
    char           *fts_accpath;  /* access path */
    char           *fts_path;     /* root path */
    short           fts_pathlen;  /* strlen(fts_path) +
                                     strlen(fts_name) */
    char           *fts_name;     /* filename */
    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;    /* [l]stat(2) information */
} FTSENT;

These fields are defined as follows:

fts_info

One of the following values describing the returned FTSENT structure and the file it represents. With the exception of directories without errors (FTS_D), all of these entries are terminal, that is, they will not be revisited, nor will any of their descendants be visited.

FTS_D

A directory being visited in preorder.

FTS_DC

A directory that causes a cycle in the tree. (The fts_cycle field of the FTSENT structure will be filled in as well.)

FTS_DEFAULT

Any FTSENT structure that represents a file type not explicitly described by one of the other fts_info values.

FTS_DNR

A directory which cannot be read. This is an error return, and the fts_errno field will be set to indicate what caused the error.

FTS_DOT

A file named "." or ".." which was not specified as a filename to fts_open() (see FTS_SEEDOT).

FTS_DP

A directory being visited in postorder. The contents of the FTSENT structure will be unchanged from when it was returned in preorder, that is, with the fts_info field set to FTS_D.

FTS_ERR

This is an error return, and the fts_errno field will be set to indicate what caused the error.

FTS_F

A regular file.

FTS_NS

A file for which no [l]stat(2) information was available. The contents of the fts_statp field are undefined. This is an error return, and the fts_errno field will be set to indicate what caused the error.

FTS_NSOK

A file for which no [l]stat(2) information was requested. The contents of the fts_statp field are undefined.

FTS_SL

A symbolic link.

FTS_SLNONE

A symbolic link with a nonexistent target. The contents of the fts_statp field reference the file characteristic information for the symbolic link itself.

fts_accpath

A path for accessing the file from the current directory.

fts_path

The path for the file relative to the root of the traversal. This path contains the path specified to fts_open() as a prefix.

fts_pathlen

The sum of the lengths of the strings referenced by fts_path and fts_name.

fts_name

The name of the file.

fts_namelen

The length of the string referenced by fts_name.

fts_level

The depth of the traversal, numbered from -1 to N, where this file was found. The FTSENT structure representing the parent of the starting point (or root) of the traversal is numbered -1, and the FTSENT structure for the root itself is numbered 0.

fts_errno

If fts_children() or fts_read() returns an FTSENT structure whose fts_info field is set to FTS_DNR, FTS_ERR, or FTS_NS, the fts_errno field contains the error number (i.e., the errno value) specifying the cause of the error. Otherwise, the contents of the fts_errno field are undefined.

fts_number

This field is provided for the use of the application program and is not modified by the fts functions. It is initialized to 0.

fts_pointer

This field is provided for the use of the application program and is not modified by the fts functions. It is initialized to NULL.

fts_parent

A pointer to the FTSENT structure referencing the file in the hierarchy immediately above the current file, that is, the directory of which this file is a member. A parent structure for the initial entry point is provided as well, however, only the fts_level, fts_number, and fts_pointer fields are guaranteed to be initialized.

fts_link

Upon return from the fts_children() function, the fts_link field points to the next structure in the NULL-terminated linked list of directory members. Otherwise, the contents of the fts_link field are undefined.

fts_cycle

If a directory causes a cycle in the hierarchy (see FTS_DC), either because of a hard link between two directories, or a symbolic link pointing to a directory, the fts_cycle field of the structure will point to the FTSENT structure in the hierarchy that references the same file as the current FTSENT structure. Otherwise, the contents of the fts_cycle field are undefined.

fts_statp

A pointer to [l]stat(2) information for the file.

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(). 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() are attempted. The fts_name field is always null-terminated.

The function fts_open() may fail and set errno for any of the errors specified for open(2) and malloc(3).

In addition, fts_open() may fail and set errno as follows:

ENOENT

Any element of path_argv was an empty string.

The function fts_close() may fail and set errno for any of the errors specified for chdir(2) and close(2).

The functions fts_read() and fts_children() may fail and set errno for any of the errors specified for chdir(2), malloc(3), opendir(3), readdir(3), and [l]stat(2).

In addition, fts_children(), fts_open(), and fts_set() may fail and set errno as follows:

EINVAL

options or instr was invalid.

For an explanation of the terms used in this section, see attributes(7).

None.

glibc 2. 4.4BSD.

Before glibc 2.23, all of the APIs described in this man page are not safe when compiling a program using the LFS APIs (e.g., when compiling with -D_FILE_OFFSET_BITS=64).

find(1), chdir(2), lstat(2), stat(2), ftw(3), qsort(3)

filefuncs.3am(3), ftw(3), mk-configure(7).

The man pages fts_children(3), fts_close(3), fts_open(3), fts_read(3) and fts_set(3) are aliases of fts(3).