Reading a variable line by line with while loop

[Ray Parrish]

Smoot Carl-Mitchell wrote:
> On Tue, 2009-12-01 at 06:57 -0800, Ray Parrish wrote:
>   
>> Ray Parrish wrote:
>>     
>> Hello again,
>>
>> OK, I understand that the | is causing a sub shell to execute for the 
>> echo command, so the variable $History even 'though declared globally, 
>> is local to the loop with the pipe, and therefore not available after 
>> the loop exits.
>>
>>     
>
> Right.  subshells do not pass their environment back to their parent.
> The read command is pretty inefficient.  You might want to learn sed.
> It is well suited to this particular task.  Something like:
>
> History=`sed 's/ /__/g' ~/.bash_history`
>
> The substitution replaces all spaces in the Bash history with __.
> Output is interpolated inline and assigned to the History variable.
>   
Thank you! That worked great! Now I wonder is there is another great sed 
command that will remove redundancy in the bash history, so no command 
line is repeated in the final results in the $History variable?

I don't mean to get you to do my programming for me, and I will begin 
studying the sed manual right after I send this to see if I can figure 
it out myself. I just thought I'd pick your brain a bit more. 8-)

Later, Ray Parrish

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