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FTS(3) UNIX Programmer's Manual FTS(3) NNAAMMEE ffttss - traverse a file hierarchy SSYYNNOOPPSSIISS ##iinncclluuddee <<ssyyss//ttyyppeess..hh>> ##iinncclluuddee <<ssyyss//ssttaatt..hh>> ##iinncclluuddee <<ffttss..hh>> _F_T_S _* ffttss__ooppeenn(_c_h_a_r _* _c_o_n_s_t _*_p_a_t_h___a_r_g_v, _i_n_t _o_p_t_i_o_n_s, _i_n_t _*_c_o_m_p_a_r_(_c_o_n_s_t _F_T_S_E_N_T _*_, _c_o_n_s_t _F_T_S_E_N_T _*_)) _F_T_S_E_N_T _* ffttss__rreeaadd(_F_T_S _*_f_t_s_p) _F_T_S_E_N_T _* ffttss__cchhiillddrreenn(_F_T_S _*_f_t_s_p) _i_n_t ffttss__sseett(_F_T_S _f_t_s_p, _F_T_S_E_N_T _*_f, _i_n_t _o_p_t_i_o_n_s) _i_n_t ffttss__cclloossee(_F_T_S _*_f_t_s_p) DDEESSCCRRIIPPTTIIOONN The ffttss functions are provided for traversing UNIX file hierarchies. The simple overview is that the ffttss__ooppeenn() function returns a ``handle'' on a file hierarchy, which is supplied to the other ffttss functions to de termine which hierarchy they operate on. The function ffttss__rreeaadd() returns a pointer to a structure describing one of the files in the file hierar chy. The function ffttss__cchhiillddrreenn() returns a pointer to a linked list of structures, each of which describes one of the files contained in a di rectory in the hierarchy. In general, directories are visited two dis tinguishable times; in preorder (before any of their descendants are visited) and in postorder (after all of their descendants have been vis ited). 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 revisit portions of the hierarchy. Two structures are defined (and typedef'd) in the include file <_f_t_s_._h>. The first is _F_T_S, the structure that represents the file hierarchy stream. The second is _F_T_S_E_N_T, the structure that represents a file in the file hierarchy. Normally, an _F_T_S_E_N_T structure is returned for every file in the file hierarchy. In this manual page, ``file'' and ``_F_T_S_E_N_T structure'' are generally interchangeable. The _F_T_S_E_N_T structure contains at least the following fields, which are described in greater detail be low: 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) */ long fts_number; /* local numeric value */ void *fts_pointer; /* local address value */ struct ftsent *fts_parent; /* parent directory */ struct ftsent *fts_link; /* cycle or next file structure */ struct stat fts_statb; /* stat(2) information */ } FTSENT; These fields are defined as follows: _f_t_s___i_n_f_o One of the following flags describing the returned _F_T_S_E_N_T 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 _f_t_s___l_i_n_k field of the _F_T_S_E_N_T structure will be filled in as well.) FTS_DEFAULT Any _F_T_S_E_N_T structure that represents a file type not explicitly described by one of the other _f_t_s___i_n_f_o values. FTS_DNR A directory which cannot be read. An error re turn; the external variable _e_r_r_n_o will be set to indicate the error. FTS_DOT A file named `.' or `..' which was not speci fied as a file name to ffttss__ooppeenn() (see FTS_SEEDOT). FTS_DP A directory being visited in postorder. The contents of the _F_T_S_E_N_T structure will be un changed from when it was returned in preorder, i.e. with the _f_t_s___i_n_f_o field set to FTS_D. FTS_ERR An error return; the external variable _e_r_r_n_o will be set to indicate the error. FTS_F A regular file. FTS_NS A file for which no stat(2) information was available. The contents of the _f_t_s___s_t_a_t_b field are undefined. An error return; the external variable _e_r_r_n_o will be set to indicate the er ror. FTS_NSOK A file for which no stat(2) information was re quested. The contents of the _f_t_s___s_t_a_t_b field are undefined. FTS_SL A symbolic link. FTS_SLNONE A symbolic link with a nonexistent target. The contents of the _f_t_s___s_t_a_t_b field contain the file characteristic information for the symbol ic link itself. _f_t_s___a_c_c_p_a_t_h A path for accessing the file from the current directory. _f_t_s___p_a_t_h The path for the file relative to the root of the traversal. This path contains the path specified to ffttss__ooppeenn() as a prefix. _f_t_s___p_a_t_h_l_e_n The length of the string referenced by _f_t_s___p_a_t_h. _f_t_s___n_a_m_e The name of the file. _f_t_s___n_a_m_e_l_e_n The length of the string referenced by _f_t_s___n_a_m_e. _f_t_s___l_e_v_e_l The depth of the traversal, numbered from -1 to N, where this file was found. The _F_T_S_E_N_T structure representing the parent of the starting point (or root) of the traversal is numbered -1, and the _F_T_S_E_N_T structure for the root itself is numbered 0. _f_t_s___n_u_m_b_e_r This field is provided for the use of the application pro gram and is not modified by the ffttss functions. It is ini tialized to 0. The fields _f_t_s___n_u_m_b_e_r and _f_t_s___p_o_i_n_t_e_r occupy the same physical location; using both may cause undefined results. _f_t_s___p_o_i_n_t_e_r This field is provided for the use of the application pro gram and is not modified by the ffttss functions. It is ini tialized to NULL. The fields _f_t_s___n_u_m_b_e_r and _f_t_s___p_o_i_n_t_e_r oc cupy the same physical location; using both may cause unde fined results. _f_t_s___p_a_r_e_n_t A pointer to the _F_T_S_E_N_T structure referencing the file in the hierarchy immediately above the current file, i.e. the directory of which this file is a member. A parent struc ture for the initial entry point is provided as well, howev er, only the _f_t_s___l_e_v_e_l, _f_t_s___n_u_m_b_e_r and _f_t_s___p_o_i_n_t_e_r fields are guaranteed to be initialized. _f_t_s___l_i_n_k The _f_t_s___l_i_n_k field has two separate uses. 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 _f_t_s___l_i_n_k field of the structure will point to the _F_T_S_E_N_T structure in the hierarchy that references the same file as the current _F_T_S_E_N_T structure. Also, upon return from the ffttss__cchhiillddrreenn() function, the _f_t_s___l_i_n_k field points to the next structure in the linked list of directory members. Otherwise, the contents of the _f_t_s___l_i_n_k field are undefined. _f_t_s___s_t_a_t_b Stat(2) information for the file. FFTTSS__OOPPEENN The ffttss__ooppeenn() 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 _o_r'ing the following values: FTS_LOGICAL This option causes the ffttss routines to return _F_T_S_E_N_T struc tures for the targets of symbolic links instead of the sym bolic links themselves. If this option is set, the only symbolic links for which _F_T_S_E_N_T structures are returned to the application are those referencing nonexistent files. Either FTS_LOGICAL or FTS_PHYSICAL _m_u_s_t be provided to the ffttss__ooppeenn() function. FTS_NOCHDIR As a performance optimization, the ffttss functions change di rectories as they walk the file hierarchy. This has the sideeffect that an application cannot rely on being in any particular directory during the traversal. The FTS_NOCHDIR option turns off this optimization, and the ffttss 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 ffttss__ooppeenn(). FTS_NOSTAT By default, returned _F_T_S_E_N_T structures contain file charac teristic information (the _s_t_a_t_b field) for each file visit ed. This option relaxes that requirement as a performance optimization, allowing the ffttss functions to set the _f_t_s___i_n_f_o field to FTS_NSOK and leave the contents of the _s_t_a_t_b field undefined. FTS_PHYSICAL This option causes the ffttss routines to return _F_T_S_E_N_T struc tures for symbolic links themselves instead of the target files they point to. If this option is set, _F_T_S_E_N_T struc tures for all symbolic links in the hierarchy are returned to the application. Either FTS_LOGICAL or FTS_PHYSICAL _m_u_s_t be provided to the ffttss__ooppeenn() function. FTS_SEEDOT By default, unless they are specified as path arguments to ffttss__ooppeenn(), any files named `.' and `..' encountered in the file hierarchy are ignored. This option causes the ffttss routines to return _F_T_S_E_N_T structures for them. FTS_XDEV This option prevents ffttss from descending into directories that have a different device number than the file from which the descent began. The argument ccoommppaarr() specifies a userdefined function which may be used to order the traversal of the hierarchy. It takes two pointers to point ers to _F_T_S_E_N_T 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 _f_t_s___a_c_c_p_a_t_h, _f_t_s___p_a_t_h and _f_t_s___p_a_t_h_l_e_n fields of the _F_T_S_E_N_T structures may _n_e_v_e_r be used in this comparison. If the _f_t_s___i_n_f_o field is set to FTS_NS or the _f_t_s___s_t_a_b field may not either. If the ccoommppaarr() argument is NULL, the directory traver sal order is unspecified except for the root paths which are traversed in the order listed in _p_a_t_h___a_r_g_v. FFTTSS__RREEAADD The ffttss__rreeaadd() function returns a pointer to an _F_T_S_E_N_T structure describ ing a file in the hierarchy. Directories (that are readable and do not cause cycles) are visited at least twice, once in preorder and once in postorder. All other files are visited at least once. (Hard links be tween 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, ffttss__rreeaadd() re turns NULL and sets the external variable _e_r_r_n_o to 0. If an error unre lated to a file in the hierarchy occurs, ffttss__rreeaadd() returns NULL and sets _e_r_r_n_o appropriately. If an error related to a returned file occurs, a pointer to an _F_T_S_E_N_T structure is returned, and _e_r_r_n_o may or may not have been set (see _f_t_s___i_n_f_o). The _F_T_S_E_N_T structures returned by ffttss__rreeaadd() may be overwritten after a call to ffttss__cclloossee() on the same file hierarchy stream, or, after a call to ffttss__rreeaadd() 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 ffttss__rreeaadd() after the _F_T_S_E_N_T structure has been returned by the function ffttss__rreeaadd() in postorder. FFTTSS__CCHHIILLDDRREENN The ffttss__cchhiillddrreenn() function returns a pointer to an _F_T_S_E_N_T structure de scribing the first entry in a linked list of the files in the directory represented by the _F_T_S_E_N_T structure most recently returned by ffttss__rreeaadd(). The list is linked through the _f_t_s___l_i_n_k field of the _F_T_S_E_N_T structure, and is ordered by the userspecified comparison function, if any. Re peated calls to ffttss__cchhiillddrreenn() will recreate this linked list. If the _F_T_S_E_N_T structure most recently returned by ffttss__rreeaadd() is not a di rectory being visited in preorder, or the directory does not contain any files, ffttss__cchhiillddrreenn() returns NULL and sets _e_r_r_n_o to zero. If an error occurs, ffttss__cchhiillddrreenn() returns NULL and sets _e_r_r_n_o appropriately. The _F_T_S_E_N_T structures returned by ffttss__cchhiillddrreenn() may be overwritten after a call to ffttss__cclloossee() on the same file hierarchy stream, or after a call to ffttss__cchhiillddrreenn() or ffttss__rreeaadd() on the same file hierarchy stream. A single buffer is used for all of the paths of all of the files in the file hierarchy. Therefore, the _f_t_s___p_a_t_h and _f_t_s___a_c_c_p_a_t_h fields are guar anteed to be NULLterminated _o_n_l_y for the file most recently returned by ffttss__rreeaadd(). To use these fields to reference any files represented by other _F_T_S_E_N_T structures will require that the path buffer be modified us ing the information contained in that _F_T_S_E_N_T structure's _f_t_s___p_a_t_h_l_e_n field. Any such modifications should be undone before further calls to ffttss__rreeaadd() are attempted. The _f_t_s___n_a_m_e field is always NULLterminated. FFTTSS__SSEETT The function ffttss__sseett() allows the user application to determine further processing for the file _f of the stream _f_t_s_p. The ffttss__sseett() function re turns 0 on success, and -1 if an error occurs. _O_p_t_i_o_n must be set to one of the following values: FTS_AGAIN Revisit the file; any file type may be revisited. The next call to ffttss__rreeaadd() will return the referenced file. The _f_t_s___s_t_a_t and _f_t_s___i_n_f_o fields of the structure will be reinitialized at that time, but no other fields will have been changed. This option is meaningful only for the most recently returned file from ffttss__rreeaadd(). Normal use is for postorder directory visits, where it causes the directory to be revisited (in both pre and postorder) 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 ffttss__rreeaadd(), the next call to ffttss__rreeaadd() returns the file with the _f_t_s___i_n_f_o and _f_t_s___s_t_a_t_b fields reinitialized to reflect the target of the symbolic link instead of the symbolic link itself. If the file is one of those most recently returned by ffttss__cchhiillddrreenn(), the _f_t_s___i_n_f_o and _f_t_s___s_t_a_t_b fields of the structure, when returned by ffttss__rreeaadd(), will reflect the target 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 _f_t_s___i_n_f_o field will be set to FTS_SLNONE. If the target of the link is a directory, the preorder re turn, followed by the return of all of its descendants, followed by a postorder return, is done. FTS_SKIP No descendants of this file are visited. The file may be one of those most recently returned by either ffttss__cchhiillddrreenn() or ffttss__rreeaadd(). FFTTSS__CCLLOOSSEE The ffttss__cclloossee() function closes a file hierarchy stream _f_t_s_p and restores the current directory to the directory from which ffttss__ooppeenn() was called to open _f_t_s_p. The ffttss__cclloossee() function returns 0 on success, and -1 if an error occurs. EERRRROORRSS The function ffttss__ooppeenn() may fail and set errno for any of the errors specified for the library functions open(2) and malloc(3). The function ffttss__cclloossee() may fail and set errno for any of the errors specified for the library functions chdir(2) and close(2). The functions FFttss__rreeaadd() and ffttss__cchhiillddrreenn() 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). SSEEEE AALLSSOO find(1), chdir(2), stat(2), qsort(3) SSTTAANNDDAARRDDSS The ffttss utility is expected to be a superset of the IEEE Std1003.11988 (``POSIX'') specification. BSD Experimental July 31, 1991 6