awk substr several times in a row

Question

I am using awk substr() to extract a sub string from the string.

For example if my string looks like this:

qwertyuiop

And I want to extract (1-3) & (6-9) characters I use this:

awk '{print (substr($1, 1, 3) substr($1, 6, 4))}'  
qweyui

How can I repeat a specific subtraction several times?

For example, I want to extract (1-3) & (6-9)(6-9)(6-9) characters to get the result like ths:

qweyuioyuioyuio

Of course I can use a command like this:

awk '{print (substr($1, 1, 3) substr($1, 6, 4) substr($1, 6, 4) substr($1, 6, 4))}'

Is there a simpler way?

Solution 1

This is one of the solutions to such a problem (messy but works).

 echo qwertyuiop | awk '{m=substr($1, 6, 4); {while (count++<3) string=string m; 
 print substr($1, 1, 3) string}}' 

 qweyuioyuioyuio

Solution 2

Yes. You can simply save the substring to a variable, then re-print it as needed. Don't forget to set a null OFS:

awk '{ print substr($1, 1, 3), x = (substr($1, 6, 4)), x, x }' OFS=

Testing:

echo "qwertyuiop" | awk '{ print substr($1, 1, 3), x = (substr($1, 6, 4)), x, x }' OFS=

Results:

qweyuioyuioyuio

---

If you need to print something more than three or four times, it may be worthwhile using a for loop:

echo "qwertyuiop" | awk '{ for(i=1;i<=5;i++) x = x substr($1, 6, 4); print substr($1, 1, 3), x }' OFS=

Results:

qweyuioyuioyuioyuioyuio

Solution 3

There is a delightful post explaining various ways of repeating string in awk.

I'll quote the most obvious:

function rep1(s,n,      r) {
# O(n) allocate/appends
# 2 lines of code
# This is the simplest possible solution that will work:
# just repeatedly append the input string onto the value
# that will be passed back, decrementing the input count
# until it reaches zero.
        while (n-->0) r = r s;
        return r;
}

PS: The large amount of space before function parameter in awk indicates that this parameter is used as temporary local variable.