Reading a variable line by line with while loop

[Ray Parrish]

James Michael Fultz wrote:
> * Ray Parrish <crp at cmc.net> [2009-12-01 16:45 -0800]:
>   
>> I have found an if statement that reduces the duplicates to only two 
>> pairs for the entire file. That's pretty good considering the number of 
>> actual duplicates there were in the file to begin with. Here is the code 
>> for that one -
>>
>> function CompressHistory {
>>      BashHistory=`cat ~/.bash_history`
>>      while read ThisCommand; do
>>            ThisCommand=${ThisCommand// /__};
>>            if  [[ "$History" =~ "$ThisCommand" ]]
>>                then
>>                    echo "nothing" >/dev/null
>>                else
>>                    History="$History $ThisCommand";
>>            fi
>>      done <<< "$BashHistory"
>>      echo "$History"
>> }
>>
>> This next bit of code has me frazzled trying to figure out the proper 
>> regular expression to say "if this string exists within the larger 
>> string". Nothing I have tried so far has worked, so here is the code, 
>> and maybe someone can correct my regular expression so it works to weed 
>> out duplicates as well.
>>
>>      BashHistory=`cat ~/.bash_history`
>>      while read ThisCommand; do
>>            ThisCommand=${ThisCommand// /__};
>>            if  [[ "$History" == [.]*$ThisCommand[.]* ]]
>>     
>
> I think you may want this.
>
> if [[ "$History" =~ .*"$ThisCommand".* ]]
>
> Also, placing '.' inside of brackets treats it as a literal character
> when used in a regex.
>
>   
>>                then
>>                    echo "nothing" >/dev/null
>>                else
>>                    History="$History $ThisCommand";
>>            fi
>>      done <<< "$BashHistory"
>>
>>  From what I have read the dot is supposed to match any character, and 
>> then the * specifies that any number of characters can appear in that 
>> position. I'm just realizing that would specify perhaps one character 
>> only, repeated to the ends of the large string before it would match.
>>     
>
> Your description of the dot and asterisk regex metacharacters is
> correct, but I think that you are confused on regular expressions and
> glob characters.
>
> Bash uses regular expressions in a [[ ... =~ ... ]] expression.
> Whereas, glob expansion could be used in a [[ ... == ... ]]  expression.
>
>   
>> I do not know how to specify that the whole front, and the whole back of 
>> the variable should be the same with the matching string in the middle 
>> of them.
>>     
OK, thanks for the tips. I did find a way to make the glob expansion 
work. [not that I know a glob expansion from anything else, just 
identifying it by the == you mentioned] Here is working code that now 
only misses one pair of duplicates in the entire file. I do not know 
what it is about that particular line that makes it not match, but it's 
kinda frustrating.

Note the curly braces around the ThisCommand variable in the if 
statement. Without them this expression would not catch any matches at all.

function CompressBashHistory {
     BashHistory=`cat ~/.bash_history`
     while read ThisCommand; do
           ThisCommand=${ThisCommand// /__};
           if  [[ "$History" == *${ThisCommand}* ]]
               then
                   echo "nothing" >/dev/null
               else
                   History="$History $ThisCommand";
           fi
     done <<< "$BashHistory"
     Command=`Xdialog --stdout --title "Ray's Bash Manager - Select 
Command to Copy" --cancel-label "Exit" --combobox "Select a Command to 
Copy to the Clipboard." 0 60 $History`
echo "$Command"
}

Here is the line that always gets repeated just once in the results -

SearchTerm="<div><a__href="index.html">Ray's__Links__Home</a>{A-Za-z0-9/<>]*</div>"

Is there something in that line that prevents it from matching itself 
when tested?

Thanks again, Ray Parrish

-- 
The Future of Technology.
http://www.rayslinks.com/The%20Future%20of%20Technology.html
Ray's Links, a variety of links to usefull things, and articles by Ray.
http://www.rayslinks.com
Writings of "The" Schizophrenic, what it's like to be a schizo, and other
things, including my poetry.
http://www.writingsoftheschizophrenic.com