1fileutil_traverse(n) file utilities fileutil_traverse(n)
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8 fileutil_traverse - Iterative directory traversal
9
11 package require Tcl 8.3
12 package require fileutil::traverse ?0.6?
14 package require fileutil
16 package require control
18 ::fileutil::traverse ?objectName? path ?option value...?
20 $traverser command ?arg arg ...?
22 $traverser files
24 $traverser foreach filevar script
26 $traverser next filevar
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30
32 This package provides objects for the programmable traversal of direc‐
33 tory hierarchies. The main command exported by the package is:
34 ::fileutil::traverse ?objectName? path ?option value...?
36 The command creates a new traversal object with an associated
37 global Tcl command whose name is objectName. This command may be
38 used to invoke various operations on the traverser. If the
39 string %AUTO% is used as the objectName then a unique name will
40 be generated by the package itself.
41 Regarding the recognized options see section OPTIONS. Note that
43 all these options can be set only during the creation of the
44 traversal object. Changing them later is not possible and causes
45 errors to be thrown if attempted.
46 The object command has the following general form:
48 $traverser command ?arg arg ...?
50 Command and its arguments determine the exact behavior of
51 the object.
52 The following commands are possible for traversal objects:
54 $traverser files
56 This method is the most highlevel one provided by traversal
57 objects. When invoked it returns a list containing the names of
58 all files and directories matching the current configuration of
59 the traverser.
60 $traverser foreach filevar script
62 The highlevel files method (see above) is based on this mid-
63 level method. When invoked it finds all files and directories
64 matching per the current configuration and executes the script
65 for each path. The current path under consideration is stored in
66 the variable named by filevar. Both variable and script live /
67 are executed in the context of the caller of the method. In the
68 method files the script simply saves the found paths into the
69 list to return.
70 $traverser next filevar
72 This is the lowest possible interface to the traverser, the core
73 all higher methods are built on. When invoked it returns a bool‐
74 ean value indicating whether it found a path matching the cur‐
75 rent configuration (True), or not (False). If a path was found
76 it is stored into the variable named by filevar, in the context
77 of the caller.
78 The foreach method simply calls this method in a loop until it
80 returned False. This method is exposed so that we are also able
81 to incrementally traverse a directory hierarchy in an event-
82 based manner.
83 Note that the traverser does follow symbolic links, except when
85 doing so would cause it to enter a link-cycle. In other words,
86 the command takes care to not lose itself in infinite loops upon
87 encountering circular link structures. Note that even links
88 which are not followed will still appear in the result.
89
91 -prefilter command_prefix
92 This callback is executed for directories. Its result determines
93 if the traverser recurses into the directory or not. The default
94 is to always recurse into all directories. The callback is
95 invoked with a single argument, the absolute path of the direc‐
96 tory, and has to return a boolean value, True when the directory
97 passes the filter, and False if not.
98 -filter command_prefix
100 This callback is executed for all paths. Its result determines
101 if the current path is a valid result, and returned by next. The
102 default is to accept all paths as valid. The callback is invoked
103 with a single argument, the absolute path to check, and has to
104 return a boolean value, True when the path passes the filter,
105 and False if not.
106 -errorcmd command_prefix
108 This callback is executed for all paths the traverser has trou‐
109 ble with. Like being unable to change into them, get their sta‐
110 tus, etc. The default is to ignore any such problems. The call‐
111 back is invoked with a two arguments, the absolute path for
112 which the error occured, and the error message. Errors thrown by
113 the filter callbacks are handled through this callback too.
114 Errors thrown by the error callback itself are not caught and
115 ignored, but allowed to pass to the caller, i.e. however invoked
116 the next. Any other results from the callback are ignored.
117
119 0.4.4 In this version the traverser's broken system for handling sym‐
120 links was replaced with one working correctly and properly enu‐
121 merating all the legal non-cyclic paths under a base directory.
122 While correct this means that certain pathological directory
124 hierarchies with cross-linked sym-links will now take about
125 O(n**2) time to enumerate whereas the original broken code man‐
126 aged O(n) due to its brokenness.
127 A concrete example and extreme case is the "/sys" hierarchy
129 under Linux where some hundred devices exist under both
130 "/sys/devices" and "/sys/class" with the two sub-hierarchies
131 linking to the other, generating millions of legal paths to enu‐
132 merate. The structure, reduced to three devices, roughly looks
133 like
134 /sys/class/tty/tty0 --> ../../dev/tty0
137 /sys/class/tty/tty1 --> ../../dev/tty1
138 /sys/class/tty/tty2 --> ../../dev/tty1
139 /sys/dev/tty0/bus
141 /sys/dev/tty0/subsystem --> ../../class/tty
142 /sys/dev/tty1/bus
143 /sys/dev/tty1/subsystem --> ../../class/tty
144 /sys/dev/tty2/bus
145 /sys/dev/tty2/subsystem --> ../../class/tty
146 When having to handle such a pathological hierarchy it is recommended
149 to use the -prefilter option to prevent the traverser from following
150 symbolic links, like so:
151 package require fileutil::traverse
154 proc NoLinks {fileName} {
156 if {[string equal [file type $fileName] link]} {
157 return 0
158 }
159 return 1
160 }
161 fileutil::traverse T /sys/devices -prefilter NoLinks
163 T foreach p {
164 puts $p
165 }
166 T destroy
167
170 This document, and the package it describes, will undoubtedly contain
171 bugs and other problems. Please report such in the category fileutil
172 of the Tcllib Trackers [http://core.tcl.tk/tcllib/reportlist]. Please
173 also report any ideas for enhancements you may have for either package
174 and/or documentation.
175 When proposing code changes, please provide unified diffs, i.e the out‐
177 put of diff -u.
178 Note further that attachments are strongly preferred over inlined
180 patches. Attachments can be made by going to the Edit form of the
181 ticket immediately after its creation, and then using the left-most
182 button in the secondary navigation bar.
183
185 directory traversal, traversal
186
188 Programming tools
189tcllib 0.6 fileutil_traverse(n)