Re: Execute all processes in the background from bash.

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• In reply to: Kevin Collins: "Re: Execute all processes in the background from bash."
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Date: 21 May 2004 21:49:18 GMT

On 2004-05-21, Kevin Collins wrote:
> In article <2h4lflF8vjh8U1@uni-berlin.de>, Chris F.A. Johnson wrote:
>> On 2004-05-20, Kevin Collins wrote:
>>> In article <7960d3ee.0405200757.2b49b50f@posting.google.com>, Doug Freyburger
>>> wrote:
>>>> Ed Morton wrote:
>>>>> Doug Freyburger wrote:
>>>>>
>>>>> > When I intend to run a command very often, I write a small script
>>>>> > and name it "x" somewhere in my path. It would be something like:
>>>>>
>>>>> > #! /bin/bash
>>>>> > time ${1} &
>>>>>
>>>>> You might want to make the above:
>>>>> time "$@" &
>>>>> so you capture arguments.
>>>>
>>>> Good point.
>>>>
>>>>> > exit
>>>>>
>>>>> No need for the exit.
>>>>
>>>> True but there isn't necessarily need for the magic number in the first
>>>> line, either. I put them into all of my scripts for cleanliness reasons.
>>>
>>> I assume you mean the "shebang" entry (#!/bin/bash)? If so, there is a need for
>>> it, unless you want all your scripts to run as /bin/sh, which you probably
>>> don't. :)
>>
>> Depending which shell you are running, scripts without a shebang
>> may be run by that shell, or by /bin/sh. For example, bash itself
>> will execute a script without a shebang, but pdksh will use
>> /bin/sh (or is it $SHELL?).
>
> Per a quick glance at the pdksh manpage, its $EXECSHELL

    Which is undefined in the instance of pdksh I'm running.

>> There are systems (probably few left now) which do not understand the
>> shebang line at all.
>>
>> And I use systems with three different locations for bash, so #!/bin/bash
>> will not work on all of them. But they usually will work on all of them
>> if there is no shebang.
>
> I was not aware of that - I stand corrected. I guess I'm just thinking of ksh
> and csh. However, what happens when someone running csh or ksh or some such
> then runs one of your scripts with no shebang?

    That depends on what system it's running on and how it's run.

    If the person is calling the script from csh, it'll use /bin/sh;
    on most Linux and *BSD systems the chances are that it will run
    without any problems.

    If called from ksh, it will run in ksh, and again, chances are
    there will not be any problems.

    Often the script will run even under a Bourne shell; that's the
    point of writing in as portable a manner as possible, saving
    POSIX, ksh or bash extensions for when they make a significant
    difference.

    Most of my scripts will run in any POSIX shell, and many in a
    Bourne shell. Otherwise, they have to be properly installed or run
    as an argument to a shell command (bash path_to_script).

> It won't be running under bash...

-- 
    Chris F.A. Johnson                  http://cfaj.freeshell.org/shell
    ===================================================================
    My code (if any) in this post is copyright 2004, Chris F.A. Johnson
    and may be copied under the terms of the GNU General Public License

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• In reply to: Kevin Collins: "Re: Execute all processes in the background from bash."
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