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man:fts_open

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()
     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 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 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 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
                             error return, and the fts_errno field  will  be
                             set to indicate what caused the error.
                 FTS_DOT     A file named "."  or ".."  which was not speci-
                             fied as a filename to fts_open() (see  FTS_SEE-
                             DOT).
                 FTS_DP      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 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 sym-
                             bolic 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  traver-
                 sal.   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 contents of the fts_errno field are undefined.
     fts_number  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.
     fts_pointer 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.
     fts_parent  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  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 directo-
                 ries,  or  a  symbolic  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
     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 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_LOGI-
                   CAL is also specified.
     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 nonex-
                   istent 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
                   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
                   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 pro-
                   vided as arguments to fts_open().
     FTS_NOSTAT    By default, returned  FTSENT  structures  reference  file
                   characteristic  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 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 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 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 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
     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, 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 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 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 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
     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_chil-
     dren() 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
     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 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  ref-
                  erenced   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  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_chil-
                  dren() 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
     attributes(7).
     allbox;  lbw34  lb  lb l l l.  Interface Attribute Value T{ fts_open(),
     fts_set(),  fts_close()  T}   Thread  safety  MT-Safe  T{   fts_read(),
     fts_children() T}   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 4.16 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 2018-02-02 FTS(3)

/data/webs/external/dokuwiki/data/pages/man/fts_open.txt · Last modified: 2019/05/17 09:32 by 127.0.0.1

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