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Re: Bash style of if-then-else?


From: Ken Irving
Subject: Re: Bash style of if-then-else?
Date: Thu, 23 Sep 2010 15:35:08 -0800
User-agent: Mutt/1.5.20 (2009-06-14)

On Thu, Sep 23, 2010 at 04:38:42PM -0500, Michael Witten wrote:
> On Mon, Aug 23, 2010 at 16:40, Eric Blake <address@hidden> wrote:
> > On 08/23/2010 03:29 PM, Peng Yu wrote:
> >>
> >> Hi,
> >>
> >> I'm wondering if there is a widely accepted coding style of bash scripts.
> >>
> >> lug.fh-swf.de/vim/vim-bash/StyleGuideShell.en.pdf
> >>
> >> I've seen the following style. Which is one is more widely accepted?
> >>
> >> if [ -f $file]; then
> >>    do something
> >> fi
> >>
> >> if [ -f $file];
> >> then
> >>    do something
> >> fi
> >
> > Neither.  You're missing adequate quoting in case $file contains spaces.
> >  More importantly, when using '[', the trailing ']' has to be its own
> > argument.  Personally, I tend to use the style with fewer lines:
> >
> > if [ -f "$file" ]; then
> >  do something
> > fi
> 
> This is also possible:
> 
>   [ -f "$file" ] && do_something
> 
> or perhaps:
> 
>   [ -f "$file" ] && {
>     do_something_0
>     do_something_1
>   }

While we're talking about style...  I prefer using 'test' rather than
'[..]' as it seems to me to be more readable.

    test -f "$file" && do_something

    test -f "$file" && {
        do_something_0
        do_something_1
        }

    if test -f $file; then
        do something
    else
        do something else
    fi

Are there actual advantages for [] over test?  I guess the former uses
one less byte than the latter.

Ken



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