changing the first occurrence only of a string in a line
alex at tweedly.net
Fri Jun 19 06:04:24 CDT 2009
I'm not going toanswer your direct question (replace first occurrence)
because that is a subset of the whole question, which I think is more
How would I remove the duplicates as described below ?
(I have assumed that in each field the tag is separated from
the content by a space, so used 'word' to extract the tag)
[I tested this in the msg box]
> put "A aaa" & tab & "B bbb" & tab & "B bb2" & "C ccc" &cr into tData
> put "A a2a" & tab & "B b2b" & tab & "B 2b2" & "C ccc" &tab& "C cc2"
> &cr after tData
> set the itemDel to tab
> repeat for each line L in tData
> put empty into lastTag
> put empty into tLine
> repeat for each item itm in L
> if word 1 of itm <> lastTag then
> put itm & tab after tLine
> put word 1 of itm into lastTag
> end if
> end repeat
> delete the last char of tLine -- trailing tab character
> put tLine & cr afer tOutput
> end repeat
> put tOutput
Peter Alcibiades wrote:
> How would you do the following in Rev?
> We have a file consisting of records with tab separated fields. Each field
> has a tag followed by contents. Some tags occur more than once in some
> records which thus have varying numbers of fields. Duplicates are always
> consecutive. I want to eliminate all the occurrences of any tag except
> the first one. The duplicate tags can occur any place in the record, but
> if they are duplicated, will always be consecutive.
> Doing this in SED is not particularly difficult, but it does require going
> out to shell, and so its not cross platform. You just change the tag
> using the local scope to something else. SED then only changes the first
> occurrence in a record. Then you use the global scope and change all of
> them. Then you go back and change the first one back to what it was. In
> fact, if using SED like this, the only thing you need it for is to do the
> local, first tag, change - once this is done, the rest can be done in Rev.
> But it would be nice to stay in Rev for the whole thing.
> Is there a way in Rev to pick the first occurence of a string in a record,
> change it and not subsequent occurences, and then move on to the next
> record and do the same thing?
> That is, mimic the 'local' editing mode of SED?
> Bet you all thought them dinosaurs like SED had to be extinct by now! But
> no, they are still trampling around in the swamps of text manipulation....
> For the sake of clarity, a record might look like this:
> A aa TAB B bb TAB B bb TAB B bb TAB C cc TAB D dd TAB D dd
> and what is wanted is to change the first occurrence of B to, for
> example !1, and the first occurence of D to, for example !2, or anyway
> something that will not occur by chance, to allow the subsequent editing
> to work globally on the file. This is what SED does in local mode.
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