Shell Programming and Scripting

Code:

# awk 'NR<6{a=sprintf("%0"NR"s","*");gsub("0","*",a); print a}' /etc/services
*
**
***
****
*****

Code:

>awk 'BEGIN{    
               while ( i < 5 )
               {
               i++
               $i=OFS="*"
               print
               $i=""
               }
               }'

Hi , you don´t need a input file , this awk has only a begin part (execuded once before any input is read).

Then we can change dinamically the number of fields ($i), and assign value to it.

Ex:

Code:

> awk 'BEGIN{$5="x";print}'
    x

As you see , with this litle trick we order awk to print the 5th field with value "x".
OFS is the Output Field Splitting ,by default its value is a blank space, we didn't change it so the output of the previous statement is four blanks (because in five fields we have 4 field separators).

Next step:

Code:

> awk 'BEGIN{$5=OFS="x";print}'
xxxxx

Here we changed the OFS to "x" so the awk prints four OFS "xxxx" and the 5th field "x".

Finally we have to set the $i variable to null cause ,if we don't do that , the variable $i will have value "*" at i postion , like in this example:

Code:

> awk 'BEGIN{ while ( i < 5 )
               {
               i++
               OFS="*"
               $i="o"
               print
               }
             }'
o
o*o
o*o*o
o*o*o*o
o*o*o*o*o

Regards

Code:

$ echo "*
> **
> ***
> ****
> *****"
*
**
***
****
*****
$

sometimes is funny how we make things complicated

what if number of * doesn't stop at 5?

But, it does. I counted. What if we were supposed to display pentagon?