Yeah its is printing as "Highest number:2", but, its not printing to new file.The following is the input file.

High fanout nets in the post compile netlist:
    Fanout  Type          Name
    --------------------------
    2       INT_NET       Net   : c_c
                          Driver: c_pad
    2       INT_NET       Net   : b_c
                          Driver: b_pad
    2       INT_NET       Net   : a_c
                          Driver: a_pad
    1       INT_NET       Net   : sum_c
                          Driver: sum_1_SUM0_0
    1       INT_NET       Net   : N_5
                          Driver: sum_1_CO0_i
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kcott's version works as you expect. Your modified version (writing lines in a loop to another file) does work here, though output is not what you want.

Read more... Code repeated; output as expected (3 kB)