Power Automate: Remove Characters From A String

Imported reference from Matthew Devaney's blog for learning purposes. Original: https://www.matthewdevaney.com/power-automate-remove-characters-from-a-string/. Author: Matthew Devaney.

Power Automate: Remove Characters From A String Posted by - Matthew Devaney on - March 17, 2024 22 Comments

A Power Automate flow can unexpectedly fail to due invalid characters in a file name. To solve this problem we can obtain the file name and use Power Automate to remove characters from a string . I will show you two approaches to do this: defining a list of non valid characters and removing them from a filename and creating a list of valid characters and keeping them in the file name. Table of Contents

Introduction: The File Name With Special Characters

Remove Characters From A String In Power Automate

Flow Expressions To Remove Characters From A String

Run The Flow To Remove Characters From A String

Understanding How The Flow To Remove Characters Works

Keep Only Valid Characters In A Text String

Flow Expressions To Keep Only Valid Characters In A Text String

Run The Flow To Keep Only Valid Characters In A String

Explaining The Flow To Keep Only Valid Characters In A String

Introduction: The File Name With Special Characters

A member of the Technology department uses a Power Automate flow to ensure filenames have only valid characters .

The flow removes any special characters from the filename. #1 Remove Invalid Characters Method

Remove Characters From A String In Power Automate

Open Power Automate and create a new instant flow to remove the non valid characters from a text string. Add all of the actions shown the image below to the flow. It will take the following steps:

Compose a string of the non valid characters to be removed from the text string Pass in the string value to be cleaned

Check each character in the string value one-by-one

Filter and remove any non-valid characters

Flow Expressions To Remove Characters From A String

Copy and paste these text values and flow expressions into the appropriate actions to quickly build the flow.

Compose: Non Valid Characters – Inputs field ~`!@#$%^&*()+|{}[] <> /?;:., Code language: HTML, XML ( xml )

Compose: Text String To Validate – Inputs field data$batch! -2024.03 .02 Code language: PHP ( php )

Select: Array Of Text String Chars To Validate – From field

range( 0 ,length(outputs( 'Compose:_Text_String_To_Validate' ))) Code language: JavaScript ( javascript )

Select: Array Of Text String Chars To Validate – Map field – Index value

indexOf(outputs( 'Compose:_Non_Valid_Characters' ), substring(outputs( 'Compose:_Text_String_To_Validate' ),item(), 1 )) Code language: JavaScript ( javascript )

Select: Array Of Text String Chars To Validate – Map field – Char value

substring(outputs( 'Compose:_Text_String_To_Validate' ),item(), 1 ) Code language: JavaScript ( javascript )

Filter array – Index Equals -1 (choose a value field) item () [ 'Index' ] Code language: CSS ( css )

Compose: Valid Text String – Inputs field

join(body( 'Select:_Array_Of_Valid_Characters' ), '' ) Code language: JavaScript ( javascript )

Run The Flow To Remove Characters From A String

After the flow is created give it a test to run ensure it works as expected. The text string in our example data$batch!-2024.03.02 is changed to databatch-20240302 .

Understanding How The Flow To Remove Characters Works

The flow successfully removes non valid characters from a string but how does it work? The flow action Select: Array Of Text String Chars To Validate builds an array of characters in the text string paired with an index number. An index of -1 means the character was not found in the string of non valid characters. Indexes with a value not equals to -1 have a non valid character.

Then we filter the array to show only valid characters in the action Filter array: Index Equals -1 .

The filtered array is transformed into a simple array of characters in Select: Array Of Valid Characters which are re-joined into a text string in the action Compose: Valid Text String . #2 Keep Only Valid Characters Method

Keep Only Valid Characters In A Text String

Compiling a list all of the non valid characters which can be found in a string is difficult. It is simpler to approach the problem by defining a list of valid characters instead. We will create another flow to illustrate this method.

Open Power Automate and create a new instant flow to remove the non valid characters from a text string. Add all of the actions shown the image below to the flow

Flow Expressions To Keep Only Valid Characters In A Text String

Copy and paste these text values and flow expressions into the appropriate actions to quickly build the flow.

Compose: Valid Characters – Inputs field

ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_-

Compose: Text String To Validate – Inputs field data$batch! -2024.03 .02 Code language: PHP ( php )

Select: Array Of Text String Chars To Validate – From field

range( 0 ,length(outputs( 'Compose:_Text_String_To_Validate' ))) Code language: JavaScript ( javascript )

Select: Array Of Text String Chars To Validate – Map field – Index value

indexOf(outputs( 'Compose:_Valid_Characters' ), substring(outputs( 'Compose:_Text_String_To_Validate' ),item(), 1 )) Code language: JavaScript ( javascript )

Select: Array Of Text String Chars To Validate – Map field – Char value

substring(outputs( 'Compose:_Text_String_To_Validate' ),item(), 1 ) Code language: JavaScript ( javascript )

Filter array: Index Does Not Equal -1 (choose a value field) item () [ 'Index' ] Code language: CSS ( css )

Compose: Valid Text String – Inputs field

join(body( 'Select:_Array_Of_Valid_Characters' ), '' ) Code language: JavaScript ( javascript )

Run The Flow To Keep Only Valid Characters In A String

Now that the flow is complete perform a test to run ensure it works properly. Once again, the text string in our example data$batch!-2024.03.02 is changed to databatch-20240302 .

Explaining The Flow To Keep Only Valid Characters In A String

Just as before, the flow action Select: Array Of Text String Chars To Validate builds an array of characters in the text string paired with an index number. An index of -1 means the character was not found in the string of non valid characters. Indexes with a value not equals to -1 have a non valid character.

But this time we filter the array differently to show only characters that do not equal -1 in the action Filter array: Index Does Not Equal -1 .

Finally we, reconstruct the simple array of characters in Select: Array Of Valid Characters are once again joined into a text string in the action Compose: Valid Text String . Did You Enjoy This Article? 😺

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