Re: Bash style of if-then-else?

[Eric Blake]

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

There is nothing wrong with the other style; however, in the style where 
'then' is on a separate line, the newline alone serves as a line 
terminator and you don't need the ';', as in:

if [ -f "$file" ]
then
  do something
fi

[On a related note, if you are talking in the context of 
autoconf-related scripts, the preference is to use 'test -f "$file"' 
rather than '[ -f "$file" ]', so as not to mix up [] with autoconf's use 
of m4 quotation characters.]

--
Eric Blake   eblake@redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org