FTS(3)                         Library Routines                         FTS(3)




NAME

       fts - 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 (*com-
       par)(const FTSENT **, const FTSENT **));

       FTSENT *fts_read (FTS *ftsp);

       FTSENT *fts_children (FTS *ftsp, int options);

       int fts_set (FTS *ftsp, FTSENT *f, int options);

       int fts_close (FTS *ftsp);


DESCRIPTION

       The fts functions are provided for traversing UNIX file hierarchies.  A
       simple overview is that the fts_open function returns a ''handle'' on a
       file hierarchy, which 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 post-order (after  all  of
       their  descendants  have been visited).  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 hierar-
       chy or prune and/or re-visit portions of the hierarchy.

       Two structures are defined (and typedef'd) in the include file <fts.h>.
       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
       struct FTSENT are generally interchangeable.  The FTSENT structure con-
       tains at least the following fields, which  are  described  in  greater
       detail below:

       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) */
            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 pre-order.

                      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 specified as
                             a file name to fts_open (see FTS_SEEDOT).

                      FTS_DP A  directory  being  visited  in post-order.  The
                             contents  of  the  FTSENT   structure   will   be
                             unchanged from when it was returned in pre-order,
                             i.e. 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 non-existent 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 traver-
                     sal.  This path contains the path specified  to  fts_open
                     as a prefix.

              fts_pathlen
                     The length of the string referenced by (fts_path)

              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 traver-
                     sal is numbered -1, and the FTSENT structure for the root
                     itself is numbered 0.

              fts_errno
                     Upon  return  of a FTSENT structure from the fts_children
                     or fts_read functions, with its  fts_info  field  set  to
                     FTS_DNR,  FTS_ERR or FTS_NS, the fts_errno field contains
                     the value of the external variable errno  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
                     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, i.e.
                     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 con-
                     tents 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 direc-
                     tories, 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 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 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_LOGI-
       CAL  or  FTS_PHYSICAL)  must be specified.  The options are selected by
       or'ing 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  non-
                     existent  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 describ-
       ing a file in the hierarchy.  Directories (that are readable and do not
       cause cycles) are visited at least twice, once in pre-order and once in
       post-order.  All other files are visited at least  once.   (Hard  links
       between  directories that do not cause cycles or symbolic links to sym-
       bolic links may cause files to be visited more than once,  or  directo-
       ries 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 post-order.


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_children  will
       recreate this linked list.

       As a special case, if fts_read has not yet been called for a hierarchy,
       fts_children will return a pointer to the files in the  logical  direc-
       tory  specified  to fts_open, i.e. the arguments specified to fts_open.
       Otherwise, if the FTSENT structure most recently returned  by  fts_read
       is  not  a  directory being visited in pre-order, 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 hierar-
       chy stream.

       Option may be set to 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.  Option must be set to
       one of the following values:

              FTS_AGAIN
                     Re-visit the file; any file type may be re-visited.   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 post-order directory  visits,  where  it  causes  the
                     directory  to  be re-visited (in both pre and post-order)
                     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 pre-order  return,
              followed  by the return of all of its descendants, followed by a
              post-order 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 a file hierarchy stream 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 the library functions open(2) and malloc(3).

       The function fts_close may fail and set errno for  any  of  the  errors
       specified for the library functions chdir(2) and close(2).

       The  functions fts_read and fts_children 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).

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

              EINVAL The options were invalid.


SEE ALSO

       find(1), chdir(2), stat(2), qsort(3)


STANDARDS

       The fts utility is expected to be included in a future POSIX  1003.1-88
       revision.



GNO                             22 January 1997                         FTS(3)

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