FTS(3) Library Functions Manual FTS(3) NAME fts -- traverse a file hierarchy LIBRARY Standard C Library (libc, -lc) SYNOPSIS #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 *, const FTSENT * const *)); FTSENT * fts_read(FTS *ftsp); FTSENT * fts_children(FTS *ftsp, int options); int fts_set(FTS *ftsp, FTSENT *f, int options); void fts_set_clientptr(FTS *ftsp, void *clientdata); void * fts_get_clientptr(FTS *ftsp); FTS * fts_get_stream(FTSENT *f); int fts_close(FTS *ftsp); DESCRIPTION The fts functions are provided for traversing Unix file hierarchies. A simple overview is that the fts_open() function returns a "handle" on a file hierarchy, which 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 pre-order (before any of their de- scendants 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" (ignoring symbolic links) or physically (visiting symbolic links), 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 hi- erarchy. 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 FTS structure contains space for a single pointer, which may be used to store application data or per-hierarchy state. The fts_set_clientptr() and fts_get_clientptr() functions may be used to set and retrieve this pointer. This is likely to be useful only when accessed from the sort comparison function, which can determine the original FTS stream of its arguments us- ing the fts_get_stream() function. The two get functions are also avail- able as macros of the same name. The FTSENT structure contains at least the following fields, which are de- scribed 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 */ u_short fts_pathlen; /* strlen(fts_path) */ char *fts_name; /* file name */ u_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(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 pre-order. 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 er- ror 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 file name to fts_open() (see FTS_SEEDOT). FTS_DP A directory being visited in post-order. The contents of the FTSENT structure will be un- changed from when it was returned in pre-order, i.e., 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 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 stat(2) information was re- quested. The contents of the fts_statp field are undefined. FTS_SL A symbolic link. FTS_SLNONE A symbolic link with a non-existent 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 pre- fix. fts_pathlen The length of the string referenced by fts_path. 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 FTS_ROOTPARENTLEVEL (-1), and the FTSENT structure for the root itself is numbered FTS_ROOTLEVEL (0). fts_errno Upon return of a FTSENT structure from the fts_children() or fts_read() functions, with its fts_info field set to FTS_DNR, FTS_ERR or FTS_NS, the fts_errno field contains the value of the external variable errno 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, i.e., the direc- tory 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 hier- archy 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 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 guaran- teed to be NUL-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 NUL-terminated. FTS_OPEN The fts_open() function takes a pointer to an array of character pointers naming one or more paths which make up a logical file hierarchy to be tra- versed. 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: FTS_COMFOLLOW This option causes any symbolic link specified as a root path to be followed immediately whether or not FTS_LOGICAL is also specified. FTS_LOGICAL This option causes the fts routines to return FTSENT struc- tures for the targets of symbolic links instead of the sym- bolic links themselves. If this option is set, the only sym- bolic links for which FTSENT structures are returned to the application are those referencing non-existent files. Either FTS_LOGICAL or FTS_PHYSICAL must be provided to the fts_open() function. FTS_NOCHDIR As a performance optimization, the fts functions change di- rectories as they walk the file hierarchy. This has the side-effect that an application cannot rely on being in any particular directory during the traversal. The FTS_NOCHDIR option turns off this optimization, and the fts functions will not change the current directory. Note that applica- tions should not themselves change their current directory and try to access files unless FTS_NOCHDIR is specified and absolute pathnames were provided as arguments to fts_open(). FTS_NOSTAT By default, returned FTSENT structures reference file charac- teristic information (the statp field) for each file visited. This option relaxes that requirement as a performance opti- mization, allowing the fts functions to set the fts_info field to FTS_NSOK and leave the contents of the statp field undefined. FTS_PHYSICAL This option causes the fts routines to return FTSENT struc- tures for symbolic links themselves instead of the target files they point to. If this option is set, FTSENT struc- tures for all symbolic links in the hierarchy are returned to the application. Either FTS_LOGICAL or FTS_PHYSICAL must be provided to the fts_open() function. FTS_SEEDOT By default, unless they are specified as path arguments to fts_open(), any files named `.' or `..' encountered in the file hierarchy are ignored. This option causes the fts rou- tines to return FTSENT structures for them. FTS_XDEV This option prevents fts from descending into directories that have a different device number than the file from which the descent began. 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 argu- ment comes before, in any order with respect to, or after, the file refer- enced 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 or- der is in the order listed in path_argv for the root paths, and in the or- der listed in the directory for everything else. FTS_READ The fts_read() 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-or- der. All other files are visited at least once. (Hard links between di- rectories 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() returns NULL and sets the external variable errno to 0. If an error unrelated to a file in the hierarchy occurs, fts_read() returns NULL and sets errno appro- priately. 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() may be overwritten after a call to fts_close() on the same file hierarchy stream, or, after a call to fts_read() 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() after the FTSENT structure has been returned by the function fts_read() in post-order. FTS_CHILDREN The fts_children() function returns a pointer to an FTSENT structure de- scribing 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(). 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() will recreate this linked list. As a special case, if fts_read() has not yet been called for a hierarchy, fts_children() will return a pointer to the files in the logical directory specified to fts_open(), i.e., the arguments specified to fts_open(). Oth- erwise, if the FTSENT structure most recently returned by fts_read() is not a directory being visited in pre-order, or the directory does not contain any files, fts_children() returns NULL and sets errno to zero. If an error occurs, fts_children() returns NULL and sets errno appropriately. The FTSENT structures returned by fts_children() may be overwritten after a call to fts_children(), fts_close() or fts_read() on the same file hierar- chy stream. Option may be set to the following value: FTS_NAMEONLY Only the names of the files are needed. The contents of all the fields in the returned linked list of structures are un- defined with the exception of the fts_name and fts_namelen fields. FTS_SET The function fts_set() allows the user application to determine further processing for the file f of the stream ftsp. The fts_set() function re- turns 0 on success, and -1 if an error occurs. Option must be set to one of the following values: FTS_AGAIN Re-visit the file; any file type may be re-visited. The next call to fts_read() will return the referenced file. The fts_stat and fts_info fields of the structure will be reini- tialized at that time, but no other fields will have been changed. This option is meaningful only for the most re- cently returned file from fts_read(). Normal use is for post-order directory visits, where it causes the directory to be re-visited (in both pre and post-order) as well as all of its descendants. FTS_FOLLOW The referenced file must be a symbolic link. If the refer- enced file is the one most recently returned by fts_read(), the next call to fts_read() returns the file with the fts_info and fts_statp fields reinitialized to reflect the target of the symbolic link instead of the symbolic link it- self. If the file is one of those most recently returned by fts_children(), the fts_info and fts_statp fields of the structure, when returned by fts_read(), will reflect the tar- get of the symbolic link instead of the symbolic link itself. In either case, if the target of the symbolic link does not exist the fields of the returned structure will be unchanged and the fts_info field will be set to FTS_SLNONE. If the target of the link is a directory, the pre-order re- turn, followed by the return of all of its descendants, fol- lowed by a post-order return, is done. FTS_SKIP No descendants of this file are visited. The file may be one of those most recently returned by either fts_children() or fts_read(). FTS_CLOSE The fts_close() function closes a file hierarchy stream ftsp and restores the current directory to the directory from which fts_open() was called to open ftsp. The fts_close() function returns 0 on success, and -1 if an er- ror occurs. ERRORS The function fts_open() may fail and set errno for any of the errors speci- fied for the library functions open(2) and malloc(3). The function fts_close() may fail and set errno for any of the errors spec- ified for the library functions chdir(2) and close(2). The functions fts_read() and fts_children() may fail and set errno for any of the errors specified for the library functions chdir(2), malloc(3), opendir(3), readdir(3) and stat(2). In addition, fts_children(), fts_open() and fts_set() may fail and set errno as follows: [EINVAL] The options were invalid. SEE ALSO find(1), chdir(2), stat(2), qsort(3) HISTORY The fts interface was first introduced in 4.4BSD. The fts_get_clientptr(), fts_get_stream(), and fts_set_clientptr() functions were introduced in FreeBSD 5.0, principally to provide for alternative interfaces to the fts functionality using different data structures. FreeBSD 5.3 September 15, 2002 FTS(3)
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | FTS_OPEN | FTS_READ | FTS_CHILDREN | FTS_SET | FTS_CLOSE | ERRORS | SEE ALSO | HISTORY
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