NAME
fts, ftsopen, ftsread, ftschildren, ftsset, ftsclose - traverse a file hierarchy SYNOPSIS
#include
#include
#include
FTS *ftsopen(char * const *pathargv, int options, int (*compar)(const FTSENT **, const FTSENT **)); FTSENT *ftsread(FTS *ftsp); FTSENT *ftschildren(FTS *ftsp, int options); int ftsset(FTS *ftsp, FTSENT *f, int options); int ftsclose(FTS *ftsp); DESCRIPTION The fts functions are provided for traversing file hierarchies. A sim‐ ple overview is that the ftsopen() function returns a "handle" on a file hierarchy, which is then supplied to the other fts functions. The function ftsread() returns a pointer to a structure describing one of the files in the file hierarchy. The function ftschildren() 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 are defined (and typedef'd) in the include file . 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 { unsigned short ftsinfo; /* flags for FTSENT structure */ char *ftsaccpath; /* access path */ char *ftspath; /* root path */ short ftspathlen; /* strlen(ftspath) */ char *ftsname; /* filename */ short ftsnamelen; /* strlen(ftsname) */ short ftslevel; /* depth (-1 to N) */ int ftserrno; /* file errno */ long ftsnumber; /* local numeric value */ void *ftspointer; /* local address value */ struct ftsent *ftsparent; /* parent directory */ struct ftsent *ftslink; /* next file structure */ struct ftsent *ftscycle; /* cycle structure */ struct stat *ftsstatp; /* stat(2) information */ } FTSENT; These fields are defined as follows: ftsinfo One of the following flags describing the returned FTSENT structure and the file it represents. With the exception of directories without errors (FTSD), all of these entries are terminal, that is, they will not be revisited, nor will any of their descendants be visited. FTSD A directory being visited in preorder. FTSDC A directory that causes a cycle in the tree. (The ftscycle field of the FTSENT structure will be filled in as well.) FTSDEFAULT Any FTSENT structure that represents a file type not explicitly described by one of the other ftsinfo values. FTSDNR A directory which cannot be read. This is an error return, and the ftserrno field will be set to indicate what caused the error. FTSDOT A file named "." or ".." which was not speci‐ fied as a filename to ftsopen() (see FTSSEE‐ DOT). FTSDP A directory being visited in postorder. The contents of the FTSENT structure will be unchanged from when it was returned in pre‐ order, that is, with the ftsinfo field set to FTSD. FTSERR This is an error return, and the ftserrno field will be set to indicate what caused the error. FTSF A regular file. FTSNS A file for which no stat(2) information was available. The contents of the ftsstatp field are undefined. This is an error return, and the ftserrno field will be set to indicate what caused the error. FTSNSOK A file for which no stat(2) information was requested. The contents of the ftsstatp field are undefined. FTSSL A symbolic link. FTSSLNONE A symbolic link with a nonexistent target. The contents of the ftsstatp field reference the file characteristic information for the sym‐ bolic link itself. ftsaccpath A path for accessing the file from the current directory. ftspath The path for the file relative to the root of the traver‐ sal. This path contains the path specified to ftsopen() as a prefix. ftspathlen The length of the string referenced by ftspath. ftsname The name of the file. ftsnamelen The length of the string referenced by ftsname.
ftslevel 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. ftserrno Upon return of a FTSENT structure from the ftschildren() or ftsread() functions, with its ftsinfo field set to FTSDNR, FTSERR or FTSNS, the ftserrno field contains the value of the external variable errno specifying the cause of the error. Otherwise, the contents of the ftserrno field are undefined. ftsnumber This field is provided for the use of the application pro‐ gram and is not modified by the fts functions. It is ini‐ tialized to 0. ftspointer This field is provided for the use of the application pro‐ gram and is not modified by the fts functions. It is ini‐ tialized to NULL. ftsparent 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 ftslevel, ftsnumber and ftspointer fields are guaranteed to be initialized. ftslink Upon return from the ftschildren() function, the ftslink
field points to the next structure in the NULL-terminated linked list of directory members. Otherwise, the contents of the ftslink field are undefined. ftscycle If a directory causes a cycle in the hierarchy (see FTSDC), either because of a hard link between two directo‐ ries, or a symbolic link pointing to a directory, the ftscycle 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 ftscycle field are undefined. ftsstatp 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 ftspath and ftsaccpath fields are
guaranteed to be null-terminated only for the file most recently returned by ftsread(). To use these fields to reference any files represented by other FTSENT structures will require that the path buf‐ fer be modified using the information contained in that FTSENT struc‐ ture's ftspathlen field. Any such modifications should be undone before further calls to ftsread() are attempted. The ftsname field
is always null-terminated. ftsopen() The ftsopen() function takes a pointer to an array of character point‐ ers 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 FTSLOGI‐ CAL or FTSPHYSICAL) must be specified. The options are selected by ORing the following values: FTSCOMFOLLOW This option causes any symbolic link specified as a root path to be followed immediately whether or not FTSLOGICAL is also specified. FTSLOGICAL This option causes the fts routines to return FTSENT structures for the targets of symbolic links instead of the symbolic links themselves. If this option is set, the only symbolic links for which FTSENT structures are returned to the application are those referencing nonexis‐ tent files. Either FTSLOGICAL or FTSPHYSICAL must be provided to the ftsopen() function. FTSNOCHDIR 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. The FTSNOCHDIR option turns off this optimization, and the fts functions will not change the current directory. Note that applications should not themselves change their cur‐ rent directory and try to access files unless FTSNOCHDIR is specified and absolute pathnames were provided as argu‐ ments to ftsopen(). FTSNOSTAT By default, returned FTSENT structures reference file characteristic information (the statp field) for each file visited. This option relaxes that requirement as a per‐ formance optimization, allowing the fts functions to set the ftsinfo field to FTSNSOK and leave the contents of the statp field undefined. FTSPHYSICAL This option causes the fts routines to return FTSENT 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. Either FTSLOGICAL or FTSPHYSICAL must be provided to the ftsopen() function. FTSSEEDOT By default, unless they are specified as path arguments to ftsopen(), any files named "." or ".." encountered in the file hierarchy are ignored. This option causes the fts routines to return FTSENT structures for them. FTSXDEV 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 argument comes before, in any order with respect to, or after, the file referenced by its second argument. The ftsaccpath, ftspath and ftspathlen fields of the FTSENT structures may never be used in this comparison. If the ftsinfo field is set to FTSNS or FTSNSOK, the ftsstatp field may not either. If the compar() argument is NULL, the directory traversal order is in the order listed in pathargv for the root paths, and in the order listed in the directory for everything else. ftsread() The ftsread() 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 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 direc‐ tories more than twice.) If all the members of the hierarchy have been returned, ftsread() returns NULL and sets the external variable errno to 0. If an error unrelated to a file in the hierarchy occurs, ftsread() 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 ftsinfo). The FTSENT structures returned by ftsread() may be overwritten after a call to ftsclose() on the same file hierarchy stream, or, after a call to ftsread() 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 ftsread() after the FTSENT structure has been returned by the function ftsread() in postorder. ftschildren() The ftschildren() 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 ftsread(). The list is linked through the
ftslink field of the FTSENT structure, and is ordered by the user- specified comparison function, if any. Repeated calls to ftschil‐ dren() will recreate this linked list. As a special case, if ftsread() has not yet been called for a hierar‐ chy, ftschildren() will return a pointer to the files in the logical directory specified to ftsopen(), that is, the arguments specified to ftsopen(). Otherwise, if the FTSENT structure most recently returned by ftsread() is not a directory being visited in preorder, or the directory does not contain any files, ftschildren() returns NULL and sets errno to zero. If an error occurs, ftschildren() returns NULL and sets errno appropriately. The FTSENT structures returned by ftschildren() may be overwritten after a call to ftschildren(), ftsclose() or ftsread() on the same file hierarchy stream. Option may be set to the following value: FTSNAMEONLY 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 the ftsname and ftsnamelen fields. ftsset() The function ftsset() allows the user application to determine further processing for the file f of the stream ftsp. The ftsset() function
returns 0 on success, and -1 if an error occurs. Option must be set to one of the following values: FTSAGAIN Revisit the file; any file type may be revisited. The next call to ftsread() will return the referenced file. The ftsstat and ftsinfo 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 ftsread(). 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. FTSFOLLOW The referenced file must be a symbolic link. If the ref‐ erenced file is the one most recently returned by ftsread(), the next call to ftsread() returns the file with the ftsinfo and ftsstatp 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 ftschildren(), the ftsinfo and ftsstatp fields of the structure, when returned by ftsread(), 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 ftsinfo field will be set to FTSSLNONE. 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. FTSSKIP No descendants of this file are visited. The file may be one of those most recently returned by either ftschil‐ dren() or ftsread(). ftsclose() The ftsclose() function closes a file hierarchy stream ftsp and restores the current directory to the directory from which ftsopen() was called to open ftsp. The ftsclose() function returns 0 on suc‐
cess, and -1 if an error occurs. ERRORS The function ftsopen() may fail and set errno for any of the errors specified for open(2) and malloc(3). The function ftsclose() may fail and set errno for any of the errors specified for chdir(2) and close(2). The functions ftsread() and ftschildren() may fail and set errno for any of the errors specified for chdir(2), malloc(3), opendir(3), read‐ dir(3) and stat(2). In addition, ftschildren(), ftsopen() and ftsset() may fail and set errno as follows: EINVAL The options were invalid. VERSIONS These functions are available in Linux since glibc2. CONFORMING TO 4.4BSD. SEE ALSO find(1), chdir(2), stat(2), ftw(3), qsort(3) COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2012-10-25 FTS(3)