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Applies to: ✅ Azure Data Explorer ✅ Azure Monitor ✅ Microsoft Sentinel
Removes leading match of the specified regular expression.
Syntax
trim_start(regex, source)
Learn more about syntax conventions.
Parameters
| Name | Type | Required | Description | 
|---|---|---|---|
| regex | string | ✔️ | The string or regular expression to be trimmed from the beginning of source. | 
| source | string | ✔️ | The source string from which to trim regex. | 
Returns
source after trimming match of regex found in the beginning of source.
Examples
Trim specific substring
The following example trims substring from the start of string_to_trim.
let string_to_trim = @"https://bing.com";
let substring = "https://";
print string_to_trim = string_to_trim,trimmed_string = trim_start(substring,string_to_trim)
Output
| string_to_trim | trimmed_string | 
|---|---|
| https://bing.com | bing.com | 
Trim non-alphanumeric characters
The following example trims all non-word characters from the beginning of the string.
range x from 1 to 5 step 1
| project str = strcat("-  ","Te st",x,@"// $")
| extend trimmed_str = trim_start(@"[^\w]+",str)
Output
| str | trimmed_str | 
|---|---|
| - Te st1// $ | Te st1// $ | 
| - Te st2// $ | Te st2// $ | 
| - Te st3// $ | Te st3// $ | 
| - Te st4// $ | Te st4// $ | 
| - Te st5// $ | Te st5// $ | 
Trim whitespace
The following example trims all spaces from the start of the string.
let string_to_trim = @"    Hello, world!    ";
let substring = @"\s+";
print
    string_to_trim = string_to_trim,
    trimmed_start = trim_start(substring, string_to_trim)
Output
| string_to_trim | trimmed_start | 
|---|---|
| Hello, world! | Hello, world! |