what is the use of substr in my macro?

[pavanae]

I have defined a field extraction in a macro as below

my_search | eval field_A="EventCode: " + EventCode + "; EventType: " + EventType + "; Message: " + substr(Message,1,100)
iseval = 0

What is meant by that? could anyone explain please.

[cmerriman]

The substr command grabs a section of text beginning at the first indicated index number Until the number of characters is reached (second number indicated). In your example, it is grabbing the first 100 characters of the field Message.
http://docs.splunk.com/Documentation/SplunkCloud/latest/SearchReference/TextFunctions

[micahkemp · Accepted solution]

substr(X,Y,Z)   Returns a substring from X based on the starting position Y and the length Z.

In the search above substr returns the first 100 characters of the Message field.