Search string array for string subset containing special characters

[CarcS]

Dear community,

I have a data application that runs 24/7 front of multiple test-rigs. For one test-rig I want to copy the test-script that is used to the folder where the related measurement data is stored for traceability. Due to a lack of other options in the test-rig software from external supplier I need to detect in a activity_log.txt file when the action (substring) "Run script: [Channel: System][Script: C:\Users\Public\.... .... ...." was done and then copy that file.

Transferred the txt file into an array of strings. I want to have the last time this string was starting with the mentioned substring in that array.

I tried via forum and NI suggestions:

* search 1D array, also with a '*' behind the substring it only searches for exact matches.

* Match First String, which functions exactly the wrong way around

* Match pattern in a for loop, which had the proper results for searching for "Run script:" but stopped working due to the special characters [ ] I guess when searching for "Run script: [Channel: System][Script: C:\Users\Public\"

It is probably something easy since I expect not to be the first with this but stuck on this for way to long now.

Any ideas are appreciated.
(LV24/64bit on Windows 10)

[GerdW]

Hi Carc,

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@CarcS wrote:

Transferred the txt file into an array of strings. I want to have the last time this string was starting with the mentioned substring in that array.

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• Reverse the string array.
• Autoindex the strings at a FOR loop.
• Stop the loop when the first string containing your substring was found.
• Use the loop index to calculate the index in the original (non-reversed) array.

Done.

[altenbach]

If using a non-indexing conditional tunnel, you don't even need to reverse.. 😄

(...and yes, if there is no match, you'll get a zero and we just need to compare the first element with the search term to see if it is valid. Not shown) 

[billko]

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@altenbach wrote:

If using a non-indexing conditional tunnel, you don't even need to reverse.. 😄

(...and yes, if there is no match, you'll get a zero and we just need to compare the first element with the search term to see if it is valid. Not shown) 

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Would it be more efficient to compare the entire array then search for the index where the first TRUE happens?  (Asked as a question, not a statement.)

Edit: oops, last, not first.

[altenbach]

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@billko wrote:

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Would it be more efficient to compare the entire array then search for the index where the first TRUE happens?  (Asked as a question, not a statement.)

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Depending on the size of the problem, allocating a full size Boolean array adds to the cost and you also need to do N comparisons, even if the match is typically near the end (very few comparisons!).

However reversing the array first is most likely a NOOP, because the compiler will leave it untouched in-place and just mark it as reversed. Basically, it will just autoindex from the back, similar to the following explicit code that operates on the non-reversed array directly. (only detailed benchmarking will be able to tell if these optimizations are made, so I prefer this version).

[altenbach]

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@billko wrote:

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This can still get problematic. If no match is found, you would get N.

[billko]

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@altenbach wrote:

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@billko wrote:

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This can still get problematic. If no match is found, you would get N.

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True.  But like your algorithm, you would need an additional check to make sure that doesn't happen.  I was mainly asking because I didn't know whether looping through a FOR loop is better or worse than using the 1D array search.  And I forgot that Booleans aren't truly one bit; it actually takes 8 bits to represent each Boolean so thanks for reminding me about that.

[crossrulz]

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@billko wrote:
And I forgot that Booleans aren't truly one bit; it actually takes 8 bits to represent each Boolean so thanks for reminding me about that.

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https://forums.ni.com/t5/BreakPoint/LabTOONS-The-secret-life-of-LabVIEW-objects/m-p/715739#M5539 

[CarcS]

Thanks for this, this partially solved my problem and at least pushed my brain in the right direction for solving the complete thing. Only thing missing was cutting the strings from the input array to the length of the search term since the search term is just a subset of the strings in the array.
Thanks for thinking along!

[CarcS · Accepted solution]

Thanks all for spending time to think along. Looking at the suggestions I guess my issue was wrongly phrased. I am not able to search with any 'equal' function since the search input I want to detect in the activity log is only the subset of what I am trying to find there. The full string I want to detect is longer than the search term.

Using the code from @altenbach I just added using only a subset of the strings in the array that equal the length of the search term. In order to be able to compare them.

Thanks for thinking along!👍