Finding the position of a sub string within a strong

[Ray Parrish]

James Michael Fultz wrote:
> * Ray Parrish <crp at cmc.net> [2009-11-29 06:09 -0800]:
>   
>> I am starting to get a grasp on what can be done with regular 
>> expressions, and I now know how to extract a sub string from within 
>> another string if I know it's offset, and length.
>>     
>
> Using regular expressions allows for matching patterns where you may not
> know exact offset and length.
>
>   
>> The thing I haven't discovered during all of this reading is a way to 
>> return the position of a substring within another string.
>>
>> How would I return the position of the sub string "zat" in the string 
>> "abczat1256"?
>>     
>
> $ echo "abczat1256" | awk '{print index($0,"zat"}'
>
>   
>> I know how to get the length of a string now, but not how to search 
>> within it yet. I have thought of a cludge which involves stripping 
>> character at a time from the front of the string into an array, but why 
>> re-invent the wheel when I'm sure there is already a simpler way to do this.
>>     
>
> You can perform some basic string manipulations in the shell itself,
> particularly using Bash (or Ksh or Zsh).  You can perform more complex
> string manipulations with sed and AWK.
>
> sed is good for string replacements within a line.  It's not so good for
> multi-line string manipulations.  You can do more than string
> replacement with sed, but it gets complicated quickly.
>
> AWK can perform all sorts of text manipulations as well as arithematic
> and is preferable sed for multi-line operations.
>   
Hello,

While reading i found the following method, which seems reasonable to me.

Position=`expr index "$String" "$SubString"`

That returns the starting position of SubString within String, and it 
even works! I'm beginning to see the possibilities as I learn more about 
bash.

Thanks for the awk pointer, but this method assigns directly to a 
variable, which is what I was looking for.

Later, Ray Parrish


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