[aur-general] Why /etc/issue starts with invisible chars?
roman.kyrylych at gmail.com
Fri Mar 21 05:50:49 EDT 2008
2008/3/21, Lyman <lymanrb at gmail.com>:
> Roman Kyrylych 写道:
> > 2008/3/21, Lyman <lymanrb at gmail.com>:
> >> Hi, all
> >> I found this issue when I was trying Sysmonitor in the package
> >> screenlets because Sysmonitor can not show my distribution name correctly.
> >> At the beginning I thought that it was a bug of screenlets, however,
> >> when I dug into its source code, I realized that it could be a "bug"
> >> introduced by Archlinux because the /etc/issue starts with some
> >> invisible chars.
> >> Here's the hexdump of /etc/issue in Archlinux. It is obviously that the
> >> first line in this file is not the distribution name.
> >> 00000000 1b 5b 48 1b 5b 32 4a 0a 41 72 63 68 20 4c 69 6e
> >> |.[H.[2J.Arch Lin|
> >> 00000010 75 78 20 28 43 6f 72 65 20 44 75 6d 70 29 20 20 |ux (Core
> >> Dump) |
> >> 00000020 5c 72 20 20 28 5c 6e 29 20 28 5c 6c 29 0a 0a |\r (\n)
> >> (\l)..|
> >> I've checked other two distribution, CentOS and Ubuntu (that's all I
> >> have at the moment), both of them presents the their name in the first line.
> >> I guess most of the applications just use the first line in /etc/issue
> >> as distribution name (so do screenlets). I think Archlinux should comply
> >> with "Rule of Least Surprise" on this issue. If the invisible chars are
> >> just for clearing screen, we can do that from the second line.
> > We already do. :-)
> > /etc/issue is *not* a way to check for distribution name. Apps that do
> > this are wrong.
> > Most distros have /etc/distroname-release files as well (that contain
> > the version, that's why it's empty in Arch).
> Things seem not that simple, though. On CentOS, I found
> /etc/redhat-release. On Ubuntu, there's no /etc/ubuntu-release but only
> /etc/lsb-release. Unfortunately, the latter one is a formatted text file
> and applications can not depend on it by a rule as simple as "the first
/etc/lsb-release is defined in LSB, maybe there are simpler ways to
get distro name on LSB compliant system, I don't know.
> Considering there's so many distributions in Linux world, it seems quite
> confusing for developers to do something absolutely "correct", right?
> I will forward these information to the developers of screenlets.
> However, I still insisted on suggesting changing /etc/issue to a
> "normal" one because I didn't see any advantages of inserting invisible
> chars in the first line. By doing just a little "favor", it will makes
> Archlinux more "compatible" && friendly to both developers and end
> users, I think.
Ok, I'll explain it in another way: /etc/issue is intended to be
customized by user,
thus software should *not* rely on it to get a distro name.
/etc/distroname-release was invented exactly to solve this issue.
If developers of screenlets wanted to make their life easier by
writing less lines of code and relying on /etc/issue to have a
distroname as first word/line - that's clearly a bug (or let's say
"wrong solution") in their code.
We will not "fix" it by changing our /etc/issue.
BTW, removing those "invisible" chars at the beginning makes the text
appear on screen without cleaning it first, so you'll see the rest of
daemons loading output.
> > Good written apps check for *existence* of /etc/arch-release file to
> > know whether they are on Arch Linux.
> > See virtualbox's installer for example how a check for distribution
> > should be made.
> Can you please point out which file is the installer? There's so many
> files in the package virtualbox-ose and I failed to find an "obvious"
> installer. Thanks.
Notice that all distros except Ubuntu use /etc/distroname-release even
those that are LSB-compliant (I believe at least Fedora is).
Roman Kyrylych (Роман Кирилич)
More information about the aur-general