Date: Sat, 06 Nov 2010 02:32:48 +0100 From: Cyrille Lefevre <cyrille.lefevre-lists@laposte.net> To: Devin Teske <dteske@vicor.com> Cc: freebsd-rc@freebsd.org Subject: Re: sysrc(8) -- a sysctl(8)-like utility for managing rc.conf(5) Message-ID: <4CD4B040.1000804@laposte.net> In-Reply-To: <1288978858.7362.154.camel@localhost.localdomain> References: <1286925182.32724.18.camel@localhost.localdomain> <1286996709.32724.60.camel@localhost.localdomain> <1287448781.5713.3.camel@localhost.localdomain> <1287510629.25599.2.camel@localhost.localdomain> <D763F474-8F19-4C65-B23F-78C9B137A8FE@vicor.com> <1288746388.7362.4.camel@localhost.localdomain> <17B64023-A64A-40DA-9CBC-A601710AB5BB@vicor.com> <1288919368.7362.35.camel@localhost.localdomain> <4CD3731C.6020501@laposte.net> <1288978858.7362.154.camel@localhost.localdomain>
next in thread | previous in thread | raw e-mail | index | archive | help
Le 05/11/2010 18:40, Devin Teske a =E9crit :
> On Fri, 2010-11-05 at 03:59 +0100, Cyrille Lefevre wrote:
>> Le 05/11/2010 02:09, Devin Teske a =E9crit :
you don't have to comment every line w/ 10+ lines of comments.
I don't agress you, it was just a proposal which is IMHO more
readable. however, it's your code and you make whatever you want
w/ it. the more important thing is that you understand it, well,
except if someone else have to maintain it also :-)
>> awkscript=3D'
>> # %s/\\$0/$0/;s/\\\\/\\/g
>> BEGIN { ...; regex=3D"^[[:space:]]*" varname "=3D" }
>=20
> Won't work.
>=20
> The point of failure here is that you've taken $varname (which is a
> positional parameter passed to the shell script function) and turned it=
> into an awk variable (which is never assigned).
you're wrong, the assignment is done later in :
awk -v varname=3D"$varname" ... "$awkscript"
> So right off the bat, your awk script will fail because regex will be
> assigned a value of:
>=20
> ^[[:space:]]*=3D
wrong too,
$ v=3D123; awk -v v=3D"$v" 'BEGIN{ r=3D"^[[:space:]]*"v"=3D"; print r; ex=
it}'
^[[:space:]]*123=3D
>> ...
>> if ( t1 ~ /[\'\$\\]/ )
>=20
> Since we're picking nits:
> - the backslash before the apostrophe is not needed.
right :-)
>> ...
>> else if ( t1 =3D=3D apos ) {
>=20
> apos needs to be a shell-expanded parameter/variable, otherwise you'll
> be forced to declare apos in the awkscript, which itself (without using=
> compound strings) will force vim syntax highlighting to break (somethin=
g
> that's not really important for the awkscript itself, but it's rather
> disconcerting to see entire oceans of miscolored text AFTER the embedde=
d
> here-document).
done in awk -v apos=3D"'" ... "$awkscript" below
>> ...
>> else if ( t1 ~ /[[:space:]];#]/ )
>> # parentheses aren't needed here, or wrap them as before
>> t1 =3D t2 =3D "\""
bad copy/paste, I was talking about the later one (null assignment)
# Null-assignment
else if ( t1 ~ /[[:space:]];#]/ )
{ t1 =3D t2 =3D "$bquot" }
should be
# Null-assignment
else if ( t1 ~ /[[:space:]];#]/ ) {
t1 =3D t2 =3D "$bquot"
}
to look like above syntax.
>> ...
>> printf "%s%c%s%c%s\n", substr(\$0, 0, matchlen), \
>> t1, awk_new_value, t2, value
>> '
>=20
> Just as before with $regex (which had $varname which is $1 which is the=
> positional parameter passed to the shell function), this will fail
> because awk_new_value is not defined by awk.
see below too ;^)
> Further, you've forgotten to conver \$0 to $0 (considering that you've
no, look at the # %s/\\$0/$0/;s/\\\\/\\/g abobe
>> # ... | ... doesn't need a final \ when wrapped after the |
>> local awk_new_value=3D"$( echo "$new_value" |
>> awk '{ gsub(/\\/, "\\\\"); gsub(/"/, "\\\""); print }' )"
>=20
> Wrong. Fail. And here's why...
>=20
> You are correct that a $( ... ) block can traverse newlines.
>=20
> However, what $( ... ) functional performs is a sub-shell. Each line
> within the $( ... ) syntax is taken as a single-line of shell to be
> executed.
>=20
> Therefore, by deleting the back-slash at the end of the line, you've
> turned one statement into two.
no, no, no, did you tried it ?
your syntax :
x=3D$(echo x \
| sed s,x,y,)
echo $x
the usual syntax :
x=3D$(echo x |
sed s,x,y,)
echo $x
both should print y or the shell is buggy ?
so, as I told you, the \ isn't needed after a |.
>> # you missed the " here
>> new_contents=3D$( tail -r "$file" 2> /dev/null )
>=20
> No, I did not. And here's why...
I was talking about the ones around $file, not the ones around $()
>> # you may want to use printf "%s" "$new_contents" instead of echo
>> # to avoid \ sequences interpretation if any
>> new_contents=3D$( echo "$new_contents" |
>> awk -v varname=3D"$varname" -v apos=3D"'" \
>> -v new_value=3D"$new_value" "$awkscript")
when I'll have time, I'll try my code against your code to see the
differences and if there is so many bad effects ?
>> also, %s|/bin/sh|$_PATH_BSHELL| && _PATH_BSHELL=3D/bin/sh
it's just an habit to hardcode path within variables and a proposal.
> Not sure where you got the bquotquot (not in my code).
in my example, the %s/quot/dquot/ statment turns bquot to bquotquot :-)
> perl(1)). You cannot perform multiple '%s///' operators separated by a
> semi-colon. You would get the error "E488: Trailing characters" in vim
it was just a synthetic form of writing, no more.
Regards,
Cyrille Lefevre
--=20
mailto:Cyrille.Lefevre-lists@laposte.net
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4CD4B040.1000804>