Date: Mon, 11 May 2015 15:44:53 -0400 From: Eric van Gyzen <vangyzen@FreeBSD.org> To: Devin Teske <dteske@FreeBSD.org>, Brooks Davis <brooks@freebsd.org> Cc: John Baldwin <jhb@FreeBSD.org>, Xin LI <delphij@FreeBSD.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: Re: svn commit: r282672 - head/etc/rc.d Message-ID: <555106B5.3010104@FreeBSD.org> In-Reply-To: <9FB76653-EF89-48E5-B4E8-A2006923B76A@FreeBSD.org> References: <201505082336.t48NaWRS080408@svn.freebsd.org> <C072FED2-FBED-4EF9-9D74-11B485594AD7@FreeBSD.org> <20150511191850.GC68045@spindle.one-eyed-alien.net> <9FB76653-EF89-48E5-B4E8-A2006923B76A@FreeBSD.org>
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On 05/11/2015 15:37, Devin Teske wrote: > >> On May 11, 2015, at 12:18 PM, Brooks Davis <brooks@freebsd.org <mailto:brooks@freebsd.org>> wrote: >> >> On Sun, May 10, 2015 at 03:45:48PM -0400, John Baldwin wrote: >>> >>>> On May 8, 2015, at 19:36, Xin LI <delphij@FreeBSD.org <mailto:delphij@FreeBSD.org>> wrote: >>>> >>>> Author: delphij >>>> Date: Fri May 8 23:36:31 2015 >>>> New Revision: 282672 >>>> URL: https://svnweb.freebsd.org/changeset/base/282672 >>>> >>>> Log: >>>> Always convert uuid to lower case. >>>> >>>> MFC after: 2 weeks >>>> >>>> Modified: >>>> head/etc/rc.d/hostid >>>> >>>> Modified: head/etc/rc.d/hostid >>>> ============================================================================== >>>> --- head/etc/rc.d/hostid Fri May 8 23:29:42 2015 (r282671) >>>> +++ head/etc/rc.d/hostid Fri May 8 23:36:31 2015 (r282672) >>>> @@ -58,7 +58,7 @@ hostid_set() >>>> >>>> valid_hostid() >>>> { >>>> - uuid=$1 >>>> + uuid=$(echo $1 | tr '[:upper:]' '[:lower:]') >>> >>> tr is in /usr/bin so this breaks systems with a separate /usr. Perhaps you could use dd with conv=lcase instead? >> >> Alterntively, a shell function "ltr" exists in rc.subr for this purpose. >> > > ltr would not work in this situation, for multiple reasons. > > 1. ltr doesn’t support character classes > 2. ltr is for replacing one or more characters (cannot be a class) with a single string (of variable length, 0+). > > In /etc/networks.subr you can see an example usage of ltr: > > 287 <https://svnweb.freebsd.org/base/head/etc/network.subr?view=markup#l287>; _punct=".-/+" > 288 <https://svnweb.freebsd.org/base/head/etc/network.subr?view=markup#l288>; ltr ${_if} "${_punct}" '_' _if > > > The result of this is to take a value of (for example) foo.bar and replace > any occurrences of period, minus, forward slash, or plus with instead > a single underscore. The result is stuffed into the variable “_if” (over- > writing previous contents which may have contained aforementioned > characters replaced with underscore). > > An attempt to use ltr in the below fashion: > > ltr $string ‘[:lower:]’ ‘[:upper:]’ somevar > > would surely fail. > > While it is indeed *possible* to write a find/replace function in native- > shell that supports character classes, it would not be a small function. > The primary issue is that you need to know what the character that > matched the class and there aren’t any built-ins that provide this info. > > For example: > > case “$src” in *[[:lower:]]*) > > will trigger when you have a lower-case character that needs conversion > to upper-case (or opposite if using *[[:upper:]]*) BUT you won’t know > what the character was that you matched (so how can you know which > upper-case character to supplant)? > > The function will have to resort to complicated substring mechanics or > any other seldom known procedure. > > I’ll have a noodle on it and see what I can come up with. It’s not exactly > immediately coming to me how to do this in any simple fashion while > maintaining efficiency (read: by not iterating over every single character > and also by not having a giant massive case statement with every letter > spelled out — coming up with a solution that embraces the use of the > character class I would believe to be more efficient). John Baldwin suggested "dd conv=lcase", since dd is in /bin. $ echo MixedCaseLetters | dd conv=lcase 2>/dev/null mixedcaseletters $ type dd dd is /bin/dd Eric
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