fts_close(3)



FTS(3)                     Linux Programmer's Manual                    FTS(3)

NAME
       fts,  fts_open, fts_read, fts_children, fts_set, fts_close - traverse a
       file hierarchy

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 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);

DESCRIPTION
       The fts functions are provided for traversing file hierarchies.  A sim-
       ple  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() re-
       turns 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 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 sym-
       bolic 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 repre-
       sents 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;    /* 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 di-
              rectories without errors (FTS_D), all of these entries are  ter-
              minal,  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  ex-
                     plicitly described by one of the other fts_info values.

              FTS_DNR
                     A  directory  which cannot be read.  This is an error re-
                     turn, 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 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 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  con-
              tents 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  di-
              rectory  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), ei-
              ther because of a hard link between two directories, or  a  sym-
              bolic  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 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  re-
       turned  by fts_read().  To use these fields to reference any files rep-
       resented 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 fur-
       ther  calls  to fts_read() are attempted.  The fts_name field is always
       null-terminated.

   fts_open()
       The fts_open() 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  FTS_LOGI-
       CAL  or  FTS_PHYSICAL)  must be specified.  The options are selected by
       ORing 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 spec-
              ified.

       FTS_LOGICAL
              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  nonexistent  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 directo-
              ries as they walk the file hierarchy.  This has the  side-effect
              that  an  application cannot rely on being in any particular di-
              rectory during the traversal.  The FTS_NOCHDIR 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 unless
              FTS_NOCHDIR is specified and absolute pathnames were provided as
              arguments to fts_open().

       FTS_NOSTAT
              By default, returned FTSENT structures reference file character-
              istic information (the statp field) for each file visited.  This
              option  relaxes  that requirement as a performance optimization,
              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 structures
              for symbolic links themselves instead of the target  files  they
              point to.  If this option is set, FTSENT structures for all sym-
              bolic 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 routines
              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  de-
              scent 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 af-
       ter, the file referenced 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  order  is  in  the  order  listed  in
       path_argv  for the root paths, and in the order listed in the directory
       for everything else.

   fts_read()
       The fts_read() function returns a pointer to an  FTSENT  structure  de-
       scribing  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, fts_read()  re-
       turns  NULL and sets the external variable errno to 0.  If an error un-
       related to a file in the hierarchy occurs, fts_read() returns NULL  and
       sets  errno  appropriately.  If an error related to a returned file oc-
       curs, 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  un-
       til  after a call to fts_read() after the FTSENT structure has been re-
       turned by the function fts_read() in postorder.

   fts_children()
       The fts_children() 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  re-
       cently 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 re-
       create this linked list.

       As a special case, if fts_read() has not yet been called for a  hierar-
       chy,  fts_children()  will return a pointer to the files in the logical
       directory specified to fts_open(), that is, the arguments specified  to
       fts_open().   Otherwise, if the FTSENT structure most recently returned
       by fts_read() is not a directory being visited in preorder, or the  di-
       rectory  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 af-
       ter a call to fts_children(), fts_close(), or fts_read()  on  the  same
       file hierarchy stream.

       The instr 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 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
       returns 0 on success, and -1 if an error occurs.

       The  instr  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
              to fts_read() will return the referenced file.  The fts_stat and
              fts_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  from
              fts_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 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 sym-
              bolic  link instead of the symbolic link itself.  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 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 fts_info field will be set
              to FTS_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  either  fts_children()  or
              fts_read().

   fts_close()
       The fts_close() function closes the file hierarchy stream  referred  to
       by  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 error occurs.

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

       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),  read-
       dir(3), and stat(2).

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

       EINVAL options or instr was invalid.

VERSIONS
       These functions are available in Linux since glibc2.

ATTRIBUTES
       For an  explanation  of  the  terms  used  in  this  section,  see  at-
       tributes(7).

       +-----------------------------------+---------------+-----------+
       |Interface                          | Attribute     | Value     |
       +-----------------------------------+---------------+-----------+
       |fts_open(), fts_set(), fts_close() | Thread safety | MT-Safe   |
       +-----------------------------------+---------------+-----------+
       |fts_read(), fts_children()         | Thread safety | MT-Unsafe |
       +-----------------------------------+---------------+-----------+

CONFORMING TO
       4.4BSD.

BUGS
       In versions of glibc before 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).

SEE ALSO
       find(1), chdir(2), stat(2), ftw(3), qsort(3)

COLOPHON
       This  page  is  part of release 5.07 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.

Linux                             2020-04-11                            FTS(3)

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