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SYNOPSIS top

#include <sys/types.h>#include <sys/stat.h>#include <fts.h>FTS *fts_open(char *const *path_argv, intoptions,typeof(int (const FTSENT **, const FTSENT **))*_Nullablecompar);FTSENT *fts_read(FTS *ftsp);FTSENT *fts_children(FTS *ftsp, intinstr);int fts_set(FTS *ftsp, FTSENT *f, intinstr);int fts_close(FTS *ftsp);

DESCRIPTION top

The fts functions are provided for traversing file hierarchies. A simple overview is that thefts_open() function returns a "handle" (of typeFTS *) that refers to a file hierarchy "stream". This handle is then supplied to the other fts functions. The functionfts_read() returns a pointer to a structure describing one of the files in the file hierarchy. The functionfts_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 isFTS, the structure that represents the file hierarchy itself. The second type isFTSENT, the structure that represents a file in the file hierarchy. Normally, anFTSENT structure is returned for every file in the file hierarchy. In this manual page, "file" and "FTSENT structure" are generally interchangeable. TheFTSENT 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 returnedFTSENT 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_DA directory being visited in preorder.FTS_DCA directory that causes a cycle in the tree. (Thefts_cycle field of theFTSENT structure will be filled in as well.)FTS_DEFAULT AnyFTSENT structure that represents a file type not explicitly described by one of the otherfts_info values.FTS_DNR A directory which cannot be read. This is an error return, and thefts_errno field will be set to indicate what caused the error.FTS_DOT A file named "." or ".." which was not specified as a filename tofts_open() (seeFTS_SEEDOT).FTS_DPA directory being visited in postorder. The contents of theFTSENT structure will be unchanged from when it was returned in preorder, that is, with thefts_info field set toFTS_D.FTS_ERR This is an error return, and thefts_errno field will be set to indicate what caused the error.FTS_FA regular file.FTS_NSA file for which no [l]stat(2) information was available. The contents of thefts_statp field are undefined. This is an error return, and thefts_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 thefts_statp field are undefined.FTS_SLA symbolic link.FTS_SLNONE A symbolic link with a nonexistent target. The contents of thefts_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 tofts_open() as a prefix.fts_pathlen The sum of the lengths of the strings referenced byfts_path andfts_name.fts_name The name of the file.fts_namelen The length of the string referenced byfts_name.fts_level The depth of the traversal, numbered from -1 to N, where this file was found. TheFTSENT structure representing the parent of the starting point (or root) of the traversal is numbered -1, and theFTSENT structure for the root itself is numbered 0.fts_errno Iffts_children() orfts_read() returns anFTSENT structure whosefts_info field is set toFTS_DNR,FTS_ERR, orFTS_NS, thefts_errno field contains the error number (i.e., theerrno value) specifying the error. Otherwise, the contents of thefts_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 theFTSENT 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 thefts_level,fts_number, andfts_pointer fields are guaranteed to be initialized.fts_link Upon return from thefts_children() function, thefts_link field points to the next structure in the NULL-terminated linked list of directory members. Otherwise, the contents of thefts_link field are undefined.fts_cycle If a directory causes a cycle in the hierarchy (seeFTS_DC), either because of a hard link between two directories, or a symbolic link pointing to a directory, thefts_cycle field of the structure will point to theFTSENT structure in the hierarchy that references the same file as the currentFTSENT structure. Otherwise, the contents of thefts_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, thefts_path andfts_accpath fields are guaranteed to be null-terminatedonly for the file most recently returned byfts_read(). To use these fields to reference any files represented by otherFTSENT structures will require that the path buffer be modified using the information contained in thatFTSENT structure'sfts_pathlen field. Any such modifications should be undone before further calls tofts_read() are attempted. Thefts_name field is always null-terminated.fts_open() Thefts_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 traversed. The array must be terminated by a null pointer. There are a number of options, at least one of which (eitherFTS_LOGICALorFTS_PHYSICAL) must be specified. The options are selected by ORing the following values:FTS_LOGICAL This option causes the fts routines to returnFTSENT structures for the targets of symbolic links instead of the symbolic links themselves. If this option is set, the only symbolic links for whichFTSENT structures are returned to the application are those referencing nonexistent files: thefts_statp field is obtained viastat(2) with a fallback tolstat(2).FTS_PHYSICAL This option causes the fts routines to returnFTSENT structures for symbolic links themselves instead of the target files they point to. If this option is set,FTSENT structures for all symbolic links in the hierarchy are returned to the application: thefts_statp field is obtained vialstat(2).FTS_COMFOLLOW This option causes any symbolic link specified as a root path to be followed immediately, as if viaFTS_LOGICAL, regardless of the primary mode.FTS_NOCHDIR As a performance optimization, the fts functions change directories 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. This option turns off this optimization, and the fts functions will not change the current directory. Note that applications should not themselves change their current directory and try to access files unlessFTS_NOCHDIRis specified and absolute pathnames were provided as arguments tofts_open().FTS_NOSTAT By default, returnedFTSENT structures reference file characteristic information (thefts_statp field) for each file visited. This option relaxes that requirement as a performance optimization, allowing the fts functions to set thefts_info field toFTS_NSOKand leave the contents of thefts_statp field undefined.FTS_SEEDOT By default, unless they are specified as path arguments tofts_open(), any files named "." or ".." encountered in the file hierarchy are ignored. This option causes the fts routines to returnFTSENT 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 argumentcompar() specifies a user-defined function which may be used to order the traversal of the hierarchy. It takes two pointers to pointers toFTSENT 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. Thefts_accpath,fts_path, andfts_pathlen fields of theFTSENT structures maynever be used in this comparison. If thefts_info field is set toFTS_NSorFTS_NSOK, thefts_statp field may not either. If thecompar() argument is NULL, the directory traversal order is in the order listed inpath_argv for the root paths, and in the order listed in the directory for everything else.fts_read() Thefts_read() function returns a pointer to anFTSENT structure describing 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 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() returns NULL and setserrno to 0. If an error unrelated to a file in the hierarchy occurs,fts_read() returns NULL and setserrno to indicate the error. If an error related to a returned file occurs, a pointer to anFTSENT structure is returned, anderrno may or may not have been set (seefts_info). TheFTSENT structures returned byfts_read() may be overwritten after a call tofts_close() on the same file hierarchy stream, or, after a call tofts_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 tofts_read() after theFTSENT structure has been returned by the functionfts_read() in postorder.fts_children() Thefts_children() function returns a pointer to anFTSENT structure describing the first entry in a NULL-terminated linked list of the files in the directory represented by theFTSENT structure most recently returned byfts_read(). The list is linked through thefts_link field of theFTSENT structure, and is ordered by the user-specified comparison function, if any. Repeated calls tofts_children() will re-create this linked list. As a special case, iffts_read() has not yet been called for a hierarchy,fts_children() will return a pointer to the files in the logical directory specified tofts_open(), that is, the arguments specified tofts_open(). Otherwise, if theFTSENT structure most recently returned byfts_read() is not a directory being visited in preorder, or the directory does not contain any files,fts_children() returns NULL and setserrno to zero. If an error occurs,fts_children() returns NULL and setserrno to indicate the error. TheFTSENT structures returned byfts_children() may be overwritten after a call tofts_children(),fts_close(), orfts_read() on the same file hierarchy stream. Theinstr argument is either zero or 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 undefined with the exception of thefts_name andfts_namelen fields.fts_set() The functionfts_set() allows the user application to determine further processing for the filef of the streamftsp. Thefts_set() function returns 0 on success, and -1 if an error occurs. Theinstr argument is either 0 (meaning "do nothing") or one of the following values:FTS_AGAIN Revisit the file; any file type may be revisited. The next call tofts_read() will return the referenced file. Thefts_stat andfts_info 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 fromfts_read(). Normal use is for postorder directory visits, where it causes the directory to be revisited (in both preorder and postorder) as well as all of its descendants.FTS_FOLLOW The referenced file must be a symbolic link. If the referenced file is the one most recently returned byfts_read(), the next call tofts_read() returns the file with thefts_info andfts_statp 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 byfts_children(), thefts_info andfts_statp fields of the structure, when returned byfts_read(), 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 thefts_info field will be set toFTS_SLNONE. If the target of the link is a directory, the preorder return, 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 eitherfts_children() orfts_read().fts_close() Thefts_close() function closes the file hierarchy stream referred to byftsp and restores the current directory to the directory from whichfts_open() was called to openftsp. Thefts_close() function returns 0 on success, and -1 if an error occurs.

ERRORS top

The functionfts_open() may fail and seterrno for any of the errors specified foropen(2) andmalloc(3). In addition,fts_open() may fail and seterrno as follows:ENOENTAny element ofpath_argv was an empty string. The functionfts_close() may fail and seterrno for any of the errors specified forchdir(2) andclose(2). The functionsfts_read() andfts_children() may fail and seterrno for any of the errors specified forchdir(2),malloc(3),opendir(3),readdir(3), and [l]stat(2). In addition,fts_children(),fts_open(), andfts_set() may fail and seterrno as follows:EINVALoptions orinstr was invalid.

ATTRIBUTES top

For an explanation of the terms used in this section, seeattributes(7). ┌────────────────────────────────────┬───────────────┬───────────┐ │Interface│Attribute│Value│ ├────────────────────────────────────┼───────────────┼───────────┤ │fts_open(),fts_set(),fts_close() │ Thread safety │ MT-Safe │ ├────────────────────────────────────┼───────────────┼───────────┤ │fts_read(),fts_children() │ Thread safety │ MT-Unsafe │ └────────────────────────────────────┴───────────────┴───────────┘

COLOPHON top

This page is part of theman-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17fts(3)

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