[mdlug] Difference between ; and &&

[John Wiersba]

Good, except for the [ command ] part.  This is correct (and similarly for command5 & 6):

# command4 executes only if command3 returns an exit status of 0
if command3
then
     command4
fi

# command6 executes only if command5 returns an exit status other than 0
if ! command5
then
       command6
fi


Date: Thu, 10 May 2012 03:09:16 -0400
>From: Aaron Kulkis <akulkis00 at gmail.com>
>Subject: Re: [mdlug] Difference between ; and &&
>To: MDLUG's Main discussion list <mdlug at mdlug.org>
>Message-ID: <4FAB699C.3070709 at gmail.com>
>Content-Type: text/plain; charset=ISO-8859-1
>
>Mat Enders wrote:
>> Hello all,
>> 
>> When stringing commands together at the command line I always use the
>> semicolon ;  I however see && used frequently and was wondering what
>> the difference was.
>> 
>> For example what is the difference between these commands:
>> 
>> apt-get update;apt-get dist-upgrade
>> and
>> apt-get update && apt-get dist-upgrade
>> 
>
>
>there are three constructs here:
>
>(A) command1 ;  command2
>(B) command3 && command4
>(C) command5 || command6
>
>(A) is shorthand for this:
>
>command1
>command2
>
># Command2 executes in all circumstances.
>
>
>(B) is shorthand for
>
>if [ command3 ]
>then
>     command4
>fi
>
># command2 executes only if command1 returns an exit-code of 0
>
>(c)is shorthand for
>
>if [ ! command5 ]
>then
>       command6
>fi
>
># command2 executes only if command5 returns an exit-code other than 0
>