RE: [Tcllib-devel] More file utilities ?

[Andreas K. <and...@Ac...>]

> Andreas Kupries wrote:
>
> > 	touch PATH
> > 		Creates empty file at PATH. Deletes any pre-existing
> > 		file in this location.
>
> For Unix users, "touch" would be a _very bad_ name for this operation --
> the shell command `touch` only updates the modification time
> of existing files, it doesn't truncate them.

See the recent discussion. clearf/truncate, etc. And arguments that we do
not need this command at all.


> > 	getfile PATH
> > 		Returns contents of file. Assumes that file is text,
> > 		and in system encoding.
> > 	putfile PATH TEXT
> > 		Writes text as the new content of the file.
> > 		Note: Does _not_ add a traling \n to the data.
>
> I usually call these "readFile" and "writeFile", after
> the analogous Haskell Standard Prelude functions.

Ok, and another proposal for the names :)

> > 	insertat PATH AT DATA
> > 		Inserts data at offset AT into the file.
> >
> > 	removeat PATH AT N
> > 		Removes N characters from the file, starting at
> > 		offset AT.
>
> No comment on the names

My latest thoughts are to name them 'insert', 'remove', 'replace'.

>, but these operations would be
> very useful to have in tcllib just so we'd have a short
> answer when newbies ask how to do this (which seems to
> come up once a month or so on c.l.t. :-)

:)

> > 	hack_file PATH KEY VAL ...
> > 		Takes the list of keys and values and applies them to
> > 		the contents of the file, via [string map].

> > 	hack_file_copy PATHin PATHout KEY VAL ...
> > 		Like hack_file, but writes the result to a different
> > 		file.

> These seem rather special-purpose.  A useful factor of the
> first one might be:

> 	updateInPlace $filename $cmdPrefix --
> 	    Reads the contents of file $filename and passes it
> 	    as an additional argument to $cmdPrefix.  Overwrites
> 	    the original file with the return value of the command.
> 	    If the command raises an error, the original file
> 	    is not modified.
>
> Then 'hack_file' could be expressed as:
>
> 	updateInPlace PATH [list string map [list KEY VAL...]]

The current implementation of hack_file is, in essence:

	proc hack_file {path args} {
	    putfile $path [string map $args [getfile $path]]
	}

Your proposal strikes me as a nice generalization of this. Thanks.

hack_file_copy is a bit redundant anyway. It can be expressed as 'file copy
+ hack_file', although writing it directly as get/map/put with different
paths might be more efficient.

Hm. updateInPlace, I was putting some 'patch' commands into the collection,
similar to the hack_file, but not quite (only one key to replace, but
multiple values, for each occurence of the key). Bianry patching anyone ?
Well, your proposal covers this as well, just a different update command ...
Yes, this seems to be the generally useful core.

Note: slightly OT, because this is not about the new commands, but an
existing one ... We have some proposals for extending fileutil::find in the
tracker (see RFEs). I thought yesterday that we can handle that by exposing
the core of going through a dir-hierarchy via a 'traversal' command taking
options.


--
	Andreas Kupries <and...@Ac...>
	Developer @ http://www.ActiveState.com, a division of Sophos
	Tel: +1 604 484 6491