Dave S. wrote:
> Synopsis: I need to delete just the first line matching an expression
> in a range of lines in which multiple lines match the expression.
>
> A little background: I'm working on a project in which we are
> converting a huge amount of Pascal code to C++. We have reasons for not
> using an off-the-shelf Pas-to-C translator, one of which is that much
> of the code we have to translate is Pascal code found in snippets in a
> diff file. A regular translator would not be able to make sense of such
> excerpts of code that are completely out of context. I've had some
> success using sed to create my own partial translator to with the
> task. Actually, I can get about three fourths of the translation done
> that way.
>
> Right now I'm working on a sed script to convert a Pascal case
> construct to a C++ switch construct. As part of this task, I
> automatically insert a break; statement just before every case in the
> construct and one break statement just before the default statement.
> That would be great, except that I end up with a break statement before
> the very first case in the switch, and I need to remove that one break
> statement, but leave the other break statements in the switch.
>
> Example:
> switch ( blah ) {
> break; <-- THIS break; HAS TO GO!
> case 1 :
> foobar();
> break;
>
> case 2 :
> foobar2();
> break;
>
> default :
> whatever();
> }
>
> So far I have this in the sed script for the purpose of deleting the
> first break:
>
> /^[ ]*switch/,/^[ ]*break;/ {
> s/^[ ]*break;\n//
> }
>
> By the way, the break; really is followed by a newline as the result of
> replacing a case statement with something like "break;\ncase".
>
> Evidently, the address range matches from switch through some break
> statement other than the first one.
>
> How can I delete just the first break statement after the switch?

seems you can use:

sed '/switch/{n; /break/d;}'

if there are some empty lines between the 'switch' and the first
'break' statement, then you may want to add

/^$/n;

right after the above 'n' sed command to skip them.

Xicheng