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\"     @(#)fts.3        8.5 (Berkeley) 4/16/94
\"
Dd October 27, 2024
Dt FTS 3
Os
Sh NAME
Nm fts ,
Nm fts_open ,
Nm fts_read ,
Nm fts_children ,
Nm fts_set ,
Nm fts_close
Nd traverse a file hierarchy
Sh LIBRARY
Lb libc
Sh SYNOPSIS
In sys/types.h
In sys/stat.h
In fts.h
Ft FTS *
Fo fts_open
Fa "char * const *path_argv"
Fa "int options"
Fa "int (*compar)(const FTSENT **, const FTSENT **)"
Fc
Ft FTSENT *
Fn fts_read "FTS *ftsp"
Ft FTSENT *
Fn fts_children "FTS *ftsp" "int options"
Ft int
Fn fts_set "FTS *ftsp" "FTSENT *f" "int options"
Ft int
Fn fts_close "FTS *ftsp"
Sh DESCRIPTION
The
Nm
functions are provided for traversing
Ux
file hierarchies.
A simple overview is that the
Fn fts_open
function returns a
Dq handle
on a file hierarchy, which is then supplied to
the other
Nm
functions.
The function
Fn fts_read
returns a pointer to a structure describing one of the files in the file
hierarchy.
The function
Fn 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
Pq before any of their descendants are visited
and in post-order
Pq after all of their descendants have been visited .
Files are visited once.
It is possible to walk the hierarchy
Dq logically
Pq ignoring symbolic links
or physically
Pq visiting symbolic links ,
order the walk of the hierarchy or prune and/or re-visit portions of
the hierarchy.
Pp
Two structures are defined
Pq and Li typedef Ap ed
in the include file
In fts.h .
The first is
Vt FTS ,
the structure that represents the file hierarchy itself.
The second is
Vt FTSENT ,
the structure that represents a file in the file
hierarchy.
Normally, an
Vt FTSENT
structure is returned for every file in the file
hierarchy.
In this manual page,
Dq file
and
Dq Vt FTSENT No structure
are generally
interchangeable.
The
Vt FTSENT
structure contains at least the following fields, which are
described in greater detail below:
Bd -literal -offset indent
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;
Ed
Pp
These fields are defined as follows:
Bl -tag -width Fa
It Fa fts_info
One of the following flags describing the returned
Vt FTSENT
structure and
the file it represents.
With the exception of directories without errors
Pq Dv FTS_D ,
all of these
entries are terminal, that is, they will not be revisited, nor will any
of their descendants be visited.
Bl -tag -width Dv
It Dv FTS_D
A directory being visited in pre-order.
It Dv FTS_DC
A directory that causes a cycle in the tree.
The
Fa fts_cycle
field of the
Vt FTSENT
structure will be filled in as well.
It Dv FTS_DEFAULT
Any
Vt FTSENT
structure that represents a file type not explicitly described
by one of the other
Fa fts_info
values.
It Dv FTS_DNR
A directory which cannot be read.
This is an error return, and the
Fa fts_errno
field will be set to indicate what caused the error.
It Dv FTS_DOT
A file named
Ql \&.
or
Ql ..
which was not specified as a file name to
Fn fts_open
(see
Dv FTS_SEEDOT ) .
It Dv FTS_DP
A directory being visited in post-order.
The contents of the
Vt FTSENT
structure will be unchanged from when
it was returned in pre-order, i.e., with the
Fa fts_info
field set to
Dv FTS_D .
It Dv FTS_ERR
This is an error return, and the
Fa fts_errno
field will be set to indicate what caused the error.
It Dv FTS_F
A regular file.
It Dv FTS_NS
A file for which no
Xr stat 2
information was available.
The contents of the
Fa fts_statp
field are undefined.
This is an error return, and the
Fa fts_errno
field will be set to indicate what caused the error.
It Dv FTS_NSOK
A file for which no
Xr stat 2
information was requested.
The contents of the
Fa fts_statp
field are undefined.
It Dv FTS_SL
A symbolic link.
It Dv FTS_SLNONE
A symbolic link with a non-existent target.
The contents of the
Fa fts_statp
field reference the file characteristic information for the symbolic link
itself.
It Dv FTS_W
A whiteout object.
El
It Fa fts_accpath
A path for accessing the file from the current directory.
It Fa fts_path
The path for the file relative to the root of the traversal.
This path contains the path specified to
Fn fts_open
as a prefix.
It Fa fts_pathlen
The length of the string referenced by
Fa fts_path .
It Fa fts_name
The name of the file.
It Fa fts_namelen
The length of the string referenced by
Fa fts_name .
It Fa fts_level
The depth of the traversal, numbered from \-1 to N, where this file
was found.
The
Vt FTSENT
structure representing the parent of the starting point (or root)
of the traversal is numbered \-1, and the
Vt FTSENT
structure for the root
itself is numbered 0.
It Fa fts_errno
Upon return of a
Vt FTSENT
structure from the
Fn fts_children
or
Fn fts_read
functions, with its
Fa fts_info
field set to
Dv FTS_DNR ,
Dv FTS_ERR
or
Dv FTS_NS ,
the
Fa fts_errno
field contains the value of the external variable
Va errno
specifying the cause of the error.
Otherwise, the contents of the
Fa fts_errno
field are undefined.
It Fa fts_number
This field is provided for the use of the application program and is
not modified by the
Nm
functions.
It is initialized to 0.
It Fa fts_pointer
This field is provided for the use of the application program and is
not modified by the
Nm
functions.
It is initialized to
Dv NULL .
It Fa fts_parent
A pointer to the
Vt 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
Fa fts_level ,
Fa fts_number
and
Fa fts_pointer
fields are guaranteed to be initialized.
It Fa fts_link
Upon return from the
Fn fts_children
function, the
Fa fts_link
field points to the next structure in the
Dv NULL Ns -terminated
linked list of directory members.
Otherwise, the contents of the
Fa fts_link
field are undefined.
It Fa fts_cycle
If a directory causes a cycle in the hierarchy (see
Dv FTS_DC ) ,
either because
of a hard link between two directories, or a symbolic link pointing to a
directory, the
Fa fts_cycle
field of the structure will point to the
Vt FTSENT
structure in the hierarchy that references the same file as the current
Vt FTSENT
structure.
Otherwise, the contents of the
Fa fts_cycle
field are undefined.
It Fa fts_statp
A pointer to
Xr stat 2
information for the file.
El
Pp
A single buffer is used for all of the paths of all of the files in the
file hierarchy.
Therefore, the
Fa fts_path
and
Fa fts_accpath
fields are guaranteed to be
Tn NUL Ns -terminated
Em only
for the file most recently returned by
Fn fts_read .
To use these fields to reference any files represented by other
Vt FTSENT
structures will require that the path buffer be modified using the
information contained in that
Vt FTSENT
structure's
Fa fts_pathlen
field.
Any such modifications should be undone before further calls to
Fn fts_read
are attempted.
The
Fa fts_name
field is always
Tn NUL Ns -terminated .
Ss FTS_OPEN
The
Fn 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
Dv NULL
pointer.
Pp
There are
a number of options, at least one of which
Po
either
Dv FTS_LOGICAL
or
Dv FTS_PHYSICAL
Pc
must be specified.
The options are selected by
Em or Ns 'ing
the following values:
Bl -tag -width Dv
It Dv FTS_COMFOLLOW
This option causes any symbolic link specified as a root path to be
followed immediately whether or not
Dv FTS_LOGICAL
is also specified.
It Dv FTS_LOGICAL
This option causes the
Nm
routines to return
Vt 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
Vt FTSENT
structures
are returned to the application are those referencing non-existent files.
Either
Dv FTS_LOGICAL
or
Dv FTS_PHYSICAL
Em must
be provided to the
Fn fts_open
function.
It Dv FTS_NOCHDIR
As a performance optimization, the
Nm
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
Dv FTS_NOCHDIR
option turns off this optimization, and the
Nm
functions will not change the current directory.
Note that applications should not themselves change their current directory
and try to access files unless
Dv FTS_NOCHDIR
is specified and absolute
pathnames were provided as arguments to
Fn fts_open .
It Dv FTS_NOSTAT
By default, returned
Vt FTSENT
structures reference file characteristic information
Pq the Fa fts_statp No field
for each file visited.
This option relaxes that requirement as a performance optimization,
allowing the
Nm
functions to set the
Fa fts_info
field to
Dv FTS_NSOK
and leave the contents of the
Fa fts_statp
field undefined.
It Dv FTS_PHYSICAL
This option causes the
Nm
routines to return
Vt FTSENT
structures for symbolic links themselves instead
of the target files they point to.
If this option is set,
Vt FTSENT
structures for all symbolic links in the
hierarchy are returned to the application.
Either
Dv FTS_LOGICAL
or
Dv FTS_PHYSICAL
Em must
be provided to the
Fn fts_open
function.
It Dv FTS_SEEDOT
By default, unless they are specified as path arguments to
Fn fts_open ,
any files named
Ql \&.
or
Ql ..
encountered in the file hierarchy are ignored.
This option causes the
Nm
routines to return
Vt FTSENT
structures for them.
It Dv FTS_WHITEOUT
Return whiteout entries, which are normally hidden.
It Dv FTS_XDEV
This option prevents
Nm
from descending into directories that have a different device number
than the file from which the descent began.
El
Pp
The argument
Fn compar
specifies a user-defined function which may be used to order the traversal
of the hierarchy.
It
takes two pointers to pointers to
Vt 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
Fa fts_accpath ,
Fa fts_path
and
Fa fts_pathlen
fields of the
Vt FTSENT
structures may
Em never
be used in this comparison.
If the
Fa fts_info
field is set to
Dv FTS_NS
or
Dv FTS_NSOK ,
the
Fa fts_statp
field may not either.
If the
Fn compar
argument is
Dv NULL ,
the directory traversal order is in the order listed in
Fa path_argv
for the root paths, and in the order listed in the directory for
everything else.
Pp
If an error occurs,
Fn fts_open
returns
Dv NULL
and sets
Va errno
appropriately.
Ss FTS_READ
The
Fn fts_read
function returns a pointer to an
Vt FTSENT
structure describing a file in
the hierarchy.
Directories
Pq 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.
Po
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
Pc .
Pp
If all the members of the hierarchy have been returned,
Fn fts_read
returns
Dv NULL
and sets the external variable
Va errno
to 0.
If an error unrelated to a file in the hierarchy occurs,
Fn fts_read
returns
Dv NULL
and sets
Va errno
appropriately.
If an error related to a returned file occurs, a pointer to an
Vt FTSENT
structure is returned, and
Va errno
may or may not have been set (see
Fa fts_info ) .
Pp
The
Vt FTSENT
structures returned by
Fn fts_read
may be overwritten after a call to
Fn fts_close
on the same file hierarchy stream, or, after a call to
Fn 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
Fn fts_read
after the
Vt FTSENT
structure has been returned by the function
Fn fts_read
in post-order.
Ss FTS_CHILDREN
The
Fn fts_children
function returns a pointer to an
Vt FTSENT
structure describing the first entry in a
Dv NULL Ns -terminated
linked list of the files in the directory represented by the
Vt FTSENT
structure most recently returned by
Fn fts_read .
The list is linked through the
Fa fts_link
field of the
Vt FTSENT
structure, and is ordered by the user-specified comparison function, if any.
Repeated calls to
Fn fts_children
will recreate this linked list.
Pp
As a special case, if
Fn fts_read
has not yet been called for a hierarchy,
Fn fts_children
will return a pointer to the files in the logical directory specified to
Fn fts_open ,
i.e., the arguments specified to
Fn fts_open .
Otherwise, if the
Vt FTSENT
structure most recently returned by
Fn fts_read
is not a directory being visited in pre-order,
or the directory does not contain any files,
Fn fts_children
returns
Dv NULL
and sets
Va errno
to zero.
If an error occurs,
Fn fts_children
returns
Dv NULL
and sets
Va errno
appropriately.
Pp
The
Vt FTSENT
structures returned by
Fn fts_children
may be overwritten after a call to
Fn fts_children ,
Fn fts_close
or
Fn fts_read
on the same file hierarchy stream.
Pp
Em Option
may be set to the following value:
Bl -tag -width Dv
It Dv 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
Fa fts_name
and
Fa fts_namelen
fields.
El
Ss FTS_SET
The function
Fn fts_set
allows the user application to determine further processing for the
file
Fa f
of the stream
Fa ftsp .
The
Fn fts_set
function
returns 0 on success, and \-1 if an error occurs.
Em Option
must be set to one of the following values:
Bl -tag -width Dv
It Dv FTS_AGAIN
Re-visit the file; any file type may be re-visited.
The next call to
Fn fts_read
will return the referenced file.
The
Fa fts_stat
and
Fa 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
Fn fts_read .
Normal use is for post-order directory visits, where it causes the
directory to be re-visited
Pq in both pre- and post-order
as well as all of its descendants.
It Dv FTS_FOLLOW
The referenced file must be a symbolic link.
If the referenced file is the one most recently returned by
Fn fts_read ,
the next call to
Fn fts_read
returns the file with the
Fa fts_info
and
Fa 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
Fn fts_children ,
the
Fa fts_info
and
Fa fts_statp
fields of the structure, when returned by
Fn 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
Fa fts_info
field will be set to
Dv FTS_SLNONE .
Pp
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.
It Dv FTS_SKIP
No descendants of this file are visited.
The file may be one of those most recently returned by either
Fn fts_children
or
Fn fts_read .
El
Ss FTS_CLOSE
The
Fn fts_close
function closes a file hierarchy stream
Fa ftsp
and restores the current directory to the directory from which
Fn fts_open
was called to open
Fa ftsp .
The
Fn fts_close
function
returns 0 on success, and \-1 if an error occurs.
Sh ERRORS
The function
Fn fts_open
may fail and set
Va errno
for any of the errors specified for the library functions
Xr open 2
and
Xr malloc 3 .
Pp
The function
Fn fts_close
may fail and set
Va errno
for any of the errors specified for the library functions
Xr chdir 2
and
Xr close 2 .
Pp
The functions
Fn fts_read
and
Fn fts_children
may fail and set
Va errno
for any of the errors specified for the library functions
Xr chdir 2 ,
Xr malloc 3 ,
Xr opendir 3 ,
Xr readdir 3
and
Xr stat 2 .
Pp
In addition,
Fn fts_children ,
Fn fts_open
and
Fn fts_set
may fail and set
Va errno
as follows:
Bl -tag -width Er
It Bq Er EINVAL
The options were invalid.
El
Sh SEE ALSO
Xr find 1 ,
Xr chdir 2 ,
Xr stat 2 ,
Xr qsort 3 ,
Xr symlink 7
Sh STANDARDS
The
Nm
utility was expected to be included in the
St -p1003.1-88
revision.
But twenty years later, it still was not included in the
St -p1003.1-2008
revision.

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