[Tcl-bugs] [ tcl-Bugs-2511011 ] [glob] can return non-existing filenames

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Bugs item #2511011, was opened at 2009-01-15 14:31
Message generated for change (Comment added) made by dgp
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Category: 36. Pathname Management
Group: obsolete: 8.5.4
Status: Open
Resolution: None
Priority: 8
Private: No
Submitted By: Mark Janssen (mpc_janssen)
Assigned to: Don Porter (dgp)
Summary: [glob] can return non-existing filenames

Initial Comment:
glob doesn't escape filenames starting with ~. This means glob by default can return filenames that 1) don't exists (annoying) or even point to a different spot all together (a user directory for instance, which is outright dangerous). 

For example:
create a file name "~test"

% foreach file [glob *] { if {![file exists $file]} {puts "huh $file doesn't exists"}}
huh ~test doesn't exists
% info pa
8.5.4

Interactive session above was with Tcl 8.5.4.
Dangerous situations can occur if a filename matches a valid user directory (~ for instance) and results of glob are used in recursive delete operations (which would lead to removal of the users home dir in this case)

It seems that me that glob should properly escape ~ as "./~test".



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>Comment By: Don Porter (dgp)
Date: 2009-08-13 13:37

Message:

Note that with VFS, this problem can be more
general than ~ expansion.  Any time the tail of
an absolute filename is recognized on its own
also as a different absolute filename, there's going
to be confusion that the pathnames returned by
[glob] do not point back the the same files whose
existence [glob] is acting upon.

Need to dig in to be sure, but it seems the right
solution is some checking within [glob] that
the paths it returns that it expects to be relative
are in fact relative, and applying some fix
(following the ./ prefixing example) to correct
any that are not.

Even that will leave some difficulties, if a 
relative path is retrieved from [glob] and
stored, and then a later mount of a filesystem
converts that stored path from relative to
absolute.  I think that level of difficulty cannot
be avoided given the dynamic view of the
filesystem Tcl exposes.  Any paths meant
to be kept around for any length of time at
all need to be in absolute form.


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Comment By: Don Porter (dgp)
Date: 2009-08-12 17:40

Message:

Reported again within 2834453.

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Comment By: Donal K. Fellows (dkf)
Date: 2009-02-24 05:40

Message:
The backslashes will have no effect; they're processed at an entirely
different level of Tcl.

The only question is what the contract for [glob] in this situation should
actually be. (Note that it is pretty clear what [glob -tails] should be
doing; it's when that option is not specified that I'm not sure what should
be happening.) Also, if things are changed then are we going to be
adversely impacting uses of [glob]? That's also important.

(Well, there's also the bizarre bugs in [file tail], but they probably
should be their own Bug...)

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Comment By: Nobody/Anonymous (nobody)
Date: 2009-02-23 18:20

Message:
Yes expansion of ~ is the culprit in this scenario. (most of?) Tcl's file
commands interpret ~ as a home directory. If [glob] does not escape ~ in a
filename it returns it is a bug in [glob]. Rewriting glob results to escape
~ is not an option. The contract of [glob] specifies it returns filenames.
If you try to argue that automatic ~ expansion is a bad thing, I am likely
to agree (it's a UNIX-ism for one) but that's unfixable without breaking
backward compatibility. 

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Comment By: Don Porter (dgp)
Date: 2009-02-04 17:42

Message:

There's a related regression
in [file tail]:

% set files [glob *oo]
~boo ~foo
% set files2 [glob -directory [pwd] *oo]
/home/dgp/cvs/tcl8.4/unix/~boo /home/dgp/cvs/tcl8.4/unix/~foo
% file tail [lindex $files2 0]
./~boo
% info patch
8.4.19


% set files [glob *oo]
~foo ~boo
% set files2 [glob -directory [pwd] *oo]
/home/dgp/cvs/tcl8.5/unix/~foo /home/dgp/cvs/tcl8.5/unix/~boo
% file tail [lindex $files2 0]
~foo
% file tail /home/dgp/cvs/tcl8.5/unix/~foo
./~foo
% info patch
8.5.6


The symptoms point to inconsistent
handling of values of the "path"
Tcl_ObjType depending on the details
of the intrep.  Same string ought
to produce same results, but do not.


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