bash vs dash (was: Re: How can I display a list of current environment variables and also recognized regular expressions....)

Karl Auer kauer at biplane.com.au
Thu May 1 23:11:30 UTC 2008


On Thu, 2008-05-01 at 18:51 -0400, John Toliver wrote:
> Thanks all.  Found exactly what I'm looking for.  It's a .pdf:
> "Bash-Beginners-Guide" which has a table of these.  I was right, they
> are called regular expressions.

There is a very useful document here called the "Advanced Bash-Scripting
Guide".

   http://tldp.org/LDP/abs/html/

You should always be aware of two things when scripting in Ubuntu:

The first is that Ubuntu does NOT use bash for system scripting, it uses
dash, which is missing some of bash's more esoteric features. If you
look at /bin/sh you will see that it is a link to /bin/dash, so you will
get dash, NOT bash, if you put "#!/bin/sh" at the top of your scripts.

The second is that bash does have quite a few extensions ("bashisms")
which will not work except with bash.

See:

   https://wiki.ubuntu.com/DashAsBinSh

Googling for "ubunto bash dash" will get you lots of other information
and comment on this Ubuntu design choice.

Regards, K.


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Karl Auer (kauer at biplane.com.au)                   +61-2-64957160 (h)
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