On Mon, 11 Oct 2004, Ramprasad A Padmanabhan wrote:
> On Mon, 2004-10-11 at 16:23, Urs Wagner wrote:
> >
> > I should comment out lines in a text file. I have a lot of troubles
> > to realize this.
> >
> > The lines
> > Alpha(a, b, c)
> > should be changed to
> > # Alpha(a, b, c)
>
> perl -pli.BAK -e 's/(?=.*Alpha\(a, b ,c\))/#/' FILENAME
Knowing how to do this in Perl is, of course, a very useful thing.
In this case though, it would also be useful to know how to do this in
your text editor. In vi/Vim, for example, you can do a --
:%s/\(Alpha(a, b, c)\)/# \1/gc
-- and this will find every instance of the string [1], show you each
instance as it is found, and ask for you to confirm the change. If it
looks right when the command finishes, save the file as normal.
I know Emacs can do this about as efficiently, but I'm not an Emacs user
so I'm not sure how to go about it.
Editors like BBEdit, UltraEdit, and even Microsoft Write / WordPad have
ways to get similar results, though it may be by way of simple replace
rather than a full regular expression match & substitution. In this
case, that's okay -- you can work with literal strings here -- but using
an editor that can do full regex search & replace is very useful. It's
worth using such an editor and getting comfortable with how it works.
[1] "Every instance" includes multiple instances on the same line,
which may or may not be what you want; take out the 'g' at the
end of the command if you only want to match the first one.
--
Chris Devers
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