On Wed, Mar 26, 2025 at 02:07:10PM -0400, Eric Sunshine wrote:
> On Wed, Mar 26, 2025 at 1:44 PM Jeff King <peff@xxxxxxxx> wrote:
> > On Tue, Mar 25, 2025 at 11:32:14PM +0000, Johannes Schindelin via GitGitGadget wrote:
> > > Let's unconfuse the script by letting it parse the first matching line
> > > and ignore the rest.
> >
> > Makes sense. I wondered if this:
> >
> > > get_version_line() {
> > > - LANG=C LC_ALL=C $CC -v 2>&1 | grep ' version '
> > > + LANG=C LC_ALL=C $CC -v 2>&1 | sed -n '/ version /{p;q}'
> >
> > might be more readable with "grep -m1", but it looks like "-m" is not in
> > POSIX. So what you wrote is probably safer.
>
> It's probably an indication that I've done too much `sed` programming,
> but I find Dscho's version more obvious. That aside, your response
> made me take a closer look at what Dscho wrote and I noticed that it
> is syntactically flawed, at least for BSD-lineage `sed`. Testing on
> macOS reveals that this is indeed so:
>
> % LANG=C LC_ALL=C cc -v 2>&1 | sed -n '/ version /{p;q}'
> sed: 1: "/ version /{p;q}": extra characters at the end of q command
>
> The problem is that the `q` function takes no arguments, but
> BSD-lineage `sed` thinks that the closing `}` is an argument rather
> than a terminator. Fixing this requires inserting a terminator after
> `q`, which will be either a newline character or a semicolon. So, the
> correct form is:
>
> sed -n '/ version /{p;q;}
Heh, I think it was the braces and semicolons that made my spider-sense
tingle, probably because I've been bitten by those subtleties in the
past.
I think just "/foo/p;q" works on GNU sed, but no idea if it does
elsewhere. What you wrote seems the safest.
-Peff
