exec sed with special arguments - comp.lang.tcl

Message from discussion exec sed with special arguments

Alexandre Ferrieux

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More options Sep 22 2008, 12:06 pm

Newsgroups: comp.lang.tcl

From: Alexandre Ferrieux <alexandre.ferri...@gmail.com>

Date: Mon, 22 Sep 2008 09:06:17 -0700 (PDT)

Local: Mon, Sep 22 2008 12:06 pm

Subject: Re: exec sed with special arguments

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On Sep 22, 5:25 pm, trighole <fabrice.bernardgran...@gmail.com> wrote:

> Hello,

> I try to use sed command with special arguments and it fails.
> 1- In deed I want to add 'TITI' before a '{' and add 'TOTO' after the
> '{' so I write
> exec sed -e '/{/aTITI' -e '/{/iTOTO' inFile > outFile
> TCL error is: missing close-brace: possible unbalanced brace in
> comment.

Beware single quote is not a metacharacter in Tcl. You want:

exec sed -e "/\{/aTITI" -e "/\{/iTOTO"

> To solve it I use \ to 'protect' the curly brace
> exec sed -e '\/{/aTITI' -e '/\{/iTOTO' inFile > outFile
> and TCL error is sed: -e expression #1, char 1: Unknown command: `''

First I think the first expression started with '/\{' and not '\/
{' (otherwise you'd have received the same punition as before).
Second, this shows you that the single quotes are passed to the
underlying program (sed) as normal characters, as explained above.
Of course usually you type all this in one of the sh or csh families,
where single quotes play a different role ;-)

> 2- I also want to replace
> //BLABLA by //BLOBLO
> exec sed -e "s//BLABLA///BLOBLO" inFile > outFile
> TCL error: sed: -e expression #1, char 0: No previous regular
> expression

After visiting sh's and (a bit of) Tcl's Quoting Hells, welcome to
sed's :-)
Though you can escape slashes this way:

exec sed -e "s/\\/\\/BLABLA/\\/\\/BLOBLO/"

or (only Tcl-quoting differs):

exec sed -e {s/\/\/BLABLA/\/\/BLOBLO/}

sed has a much nicer tool: you can use any character instead of "/" as
the s-command arg separator. So choose one that doesn't collide with
your own regexp and you're saved:

exec sed -e s@//BLABLA@//BLOBLO@

-Alex

> To solve it I use \ to 'protect' /
> I still got the same error.

> Can U help me

> thanks

> fab

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