fts.3

早期freebsd实现

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.Dd April 16, 1994
.Dt FTS 3
.Os
.Sh NAME
.Nm fts
.Nd traverse a file hierarchy
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/stat.h>
.Fd #include <fts.h>
.Ft FTS *
.Fn fts_open "char * const *path_argv" "int options" "int *compar(const FTSENT **, const FTSENT **)"
.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 fts
functions are provided for traversing
.Tn UNIX
file hierarchies.
A simple overview is that the
.Fn fts_open
function returns a ``handle'' on a file hierarchy, which is then supplied to
the other
.Nm fts
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
(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 hierarchy or
prune and/or re-visit portions of the hierarchy.
.Pp
Two structures are defined (and typedef'd) in the include file
.Aq Pa fts.h .
The first is
.Fa FTS ,
the structure that represents the file hierarchy itself.
The second is
.Fa FTSENT ,
the structure that represents a file in the file
hierarchy.
Normally, an
.Fa FTSENT
structure is returned for every file in the file
hierarchy.
In this manual page, ``file'' and
.Dq Fa FTSENT No structure
are generally
interchangeable.
The
.Fa FTSENT
structure contains at least the following fields, which are
described in greater detail below:
.Bd -literal
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 "fts_namelen"
.It Fa fts_info
One of the following flags describing the returned
.Fa 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 FTS_DEFAULT
.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
.Fa FTSENT
structure will be filled in as well.)
.It Dv FTS_DEFAULT
Any
.Fa 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
.Fa 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.
.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
.Fa FTSENT
structure representing the parent of the starting point (or root)
of the traversal is numbered \-1, and the
.Fa FTSENT
structure for the root
itself is numbered 0.
.It Fa fts_errno
Upon return of a
.Fa 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 fts
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 fts
functions.
It is initialized to
.Dv NULL .
.It Fa fts_parent
A pointer to the
.Fa 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 NULL-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
.Fa FTSENT
structure in the hierarchy that references the same file as the current
.Fa 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
.Dv NULL 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
.Fa FTSENT
structures will require that the path buffer be modified using the
information contained in that
.Fa 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
.Dv NULL Ns -terminated.
.Sh 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 (either
.Dv FTS_LOGICAL
or
.Dv FTS_PHYSICAL )
must be specified.
The options are selected by
.Em or Ns 'ing
the following values:
.Bl -tag -width "FTS_PHYSICAL"
.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 fts
routines to return
.Fa 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
.Fa FTSENT
structures
are returned to the application are those referencing non-existent files.
Either
.Dv FTS_LOGICAL
or
.Dv FTS_PHYSICAL
.Em must