[gentoo-user] Re: [OT] bash script advice/criticism wanted
Bo Ørsted Andresen [EMAIL PROTECTED] wrote: Also things like [[ $foo == ]] should rather be [[ -n $foo ]] but that's a minor. [[ -z $foo ]] seems to work much better. ;) -- [EMAIL PROTECTED] mailing list
Re: [gentoo-user] Re: [OT] bash script advice/criticism wanted
»Q« writes:
On Sun, 19 Aug 2007 07:10:30 +0200
Bo Ørsted Andresen [EMAIL PROTECTED] wrote:
On Sunday 19 August 2007 04:00:45 »Q« wrote:
It works as it is, but I'm interested in learning about any newbie
traps into which I might be falling or about any better practices I
should use. This is my first attempt at printing a usage message or
parsing arguments.
The script is at http://remarqs.net/misc/mids2urls.sh.txt. Feel
free to reply to me off-list (or just to flame me) if you think
this kind of non-Gentoo-specific stuff has no place here.
It's hardly the best place to ask this kind of question but
anyway.. :p
Right :) But a I like bash-scripting I also think I should start
learning python, but I need my scripts to work on old Solaris
installations, where I do not like to install perl, python and such. ANd
probably I am not allowed to so so anyway. That's why I chose bash for
them. Well, I was surprised how much I could accomplish with that. The
size of my application is now 250k and still growing.
Yeah. Thanks for having a look at it anyway. Is there a list or group
that welcomes this kind of stuff? I looked but couldn't find one.
There is comp.unix.shell.
And read the Advanced Bash Scripting Guide:
http://tldp.org/LDP/abs/html/
The most noticeable thing which is wrong with this script is the
quoting inside the brackets [ ]. Since you use bash you should just
use [[ ]] instead (which makes most of the quoting in them
unneeded..). Also things like [[ $foo == ]] should rather be [[ -n
$foo ]] but that's a minor.
I always use [[ $foo ]] only.
Also, instead of
if [ ! -f $1 ]
I like
if ! (( $# )) # $# is the number of arguments
better. BTW, shift $(($OPTIND - 1)) can also be written as shift
$((OPTIND-1)) - you do not need the $ inside (( )) contructions. They are
quite powerful, I did not expect bash to do C-like things like this:
for (( i=0; i 10*foo; i++ ))
Finally the number of calls to grep, sed and tr clearly shows that
you could improve your knowledge about sed.. ;)
Yeah, very true.
I also tend to avoid grep and sed, at least if I need performance.
Exampes:
if echo $var | grep bla
can be written as:
if [[ $var == *bla* ]]
I replace simple if-then statemens by :
if [ $QUIET == no ]
then
echo -e $URLLIST
fi
--
[[ $QUIET == no ]]
echo -e $URLLIST
Some more things:
THIS_SCRIPT=$(basename $0)
--
THIS_SCRIPT=${0##*/} (strip everything from $0 until the last / from
the
left).
Okay, there is basename and dirname, but they are external comands. If I
like to use them, I define them like this:
basename()
{
local basename=${1##*/}
echo ${basename%${2:-}}
}
dirname()
{
echo ${1%/*}
}
Have a look at all these {} constructions, they are very powerful.
In longer scripts, I define all variables I use, and with set -u I make
bash issue errors if it encounters undefined ones. This helps in case I
make a type (using $fooo instead of $foo), which otherwise would just
give an empty string.
One last thing is that I so not like the ; at the end of lines. I put the
thens, dos and such into the next, under their corrsponding ifs and
whiles. Looks better to me. Same goes for the starting { in functions.
BTW, after . || or |, a \ is not needed if the statement continues in
the next line. Also, foo=$( ) can always be written without
the .
Have fun with bash,
Wonko
--
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[gentoo-user] Re: [OT] bash script advice/criticism wanted
On Sun, 19 Aug 2007 10:43:18 +0200 Alex Schuster [EMAIL PROTECTED] wrote: There is comp.unix.shell. Thanks. I'll go there from now on. And read the Advanced Bash Scripting Guide: http://tldp.org/LDP/abs/html/ I had been reading the ABS doc, but parts of it made more sense after the input from you and Bo. I've digested most of it, and the script looks a lot different. Bo will be happy that sed is only called once (and no grep or tr), and you should be somewhat more happy with my conditionals and some other things. The updated version is at that same URL, http://remarqs.net/misc/mids2urls.sh.txt. -- [EMAIL PROTECTED] mailing list
[gentoo-user] Re: [OT] bash script advice/criticism wanted
[EMAIL PROTECTED] wrote: On Sat, Aug 18, 2007 at 09:00:45PM -0500, ?Q? wrote: The script is at http://remarqs.net/misc/mids2urls.sh.txt. Feel free to reply to me off-list (or just to flame me) if you think this kind of non-Gentoo-specific stuff has no place here. I took a quick look and about the only advice I'd give is ... use perl! or python or ruby, or whatever language rocks your boat. I learned perl because a small project I did involved text processing and it got uglier and uglier the more I tried to trick awk, sed, grep, sort, and all the usual suspects into doing the job. I finally decided to learn perl and did that and got the job done in half the time I had spent trying the usual suspects. Since then, I have gone straight to perl for any script which has to do anything as fancy as get options or parse text. I'm ok with grep and sed s, but not much more. I guess I'll (try to) learn perl if I have any serious text processing to do. But for now, I'm going to be stubborn and stick with bash. Bash makes scripting more powerful than the old bourne shell, but it doesn't make it any easier. I know it's not the advice you wanted :-) Heh, I can't always get what I want -- [EMAIL PROTECTED] mailing list
[gentoo-user] Re: [OT] bash script advice/criticism wanted
On Sun, 19 Aug 2007 07:10:30 +0200 Bo Ørsted Andresen [EMAIL PROTECTED] wrote: On Sunday 19 August 2007 04:00:45 »Q« wrote: It works as it is, but I'm interested in learning about any newbie traps into which I might be falling or about any better practices I should use. This is my first attempt at printing a usage message or parsing arguments. The script is at http://remarqs.net/misc/mids2urls.sh.txt. Feel free to reply to me off-list (or just to flame me) if you think this kind of non-Gentoo-specific stuff has no place here. It's hardly the best place to ask this kind of question but anyway.. :p Yeah. Thanks for having a look at it anyway. Is there a list or group that welcomes this kind of stuff? I looked but couldn't find one. The most noticeable thing which is wrong with this script is the quoting inside the brackets [ ]. Since you use bash you should just use [[ ]] instead (which makes most of the quoting in them unneeded..). Also things like [[ $foo == ]] should rather be [[ -n $foo ]] but that's a minor. Thanks much. And thanks for the link. Finally the number of calls to grep, sed and tr clearly shows that you could improve your knowledge about sed.. ;) Yeah, very true. http://wooledge.org/mywiki/BashFAQ#head-b1c292ce2f4fdfa6a7b5389da1892d65b6f37cda -- [EMAIL PROTECTED] mailing list
