awk-to-print-all-columns-from-the-nth-to-the-last

Question

https://www.gnu.org/software/gawk/manual/gawk.html based on section 1.1.2 1.1.2 Running awk Without Input Files I can understand awk '{print $0}' marks.txt it's just like echo. it will return

1)  Amit    Physics  80
2)  Rahul   Maths    90
3)  Shyam   Biology  87
4)  Kedar   English  85
5)  Hari    History  89

https://stackoverflow.com/questions/2961635/using-awk-to-print-all-columns-from-the-nth-to-the-last?answertab=votes#tab-top

The following code also work as expected.

awk '{print $0}' marks.txt  | awk '{print $2 "\t" $3 "\t"$4}'

I don't understand awk '{$1=""; print $0}' marks.txt Even though now intuitively make sense.

Answer 1

$1=""; print $0 clears the first field and recalculates the whole line before printing it. This is documented in the Changing Fields section of the GAWK manual:

When the value of a field is changed (as perceived by awk), the text of the input record is recalculated to contain the new field where the old one was. In other words, $0 changes to reflect the altered field.

This is true in all implementations of AWK, it’s not a GNU extension; The AWK Programming Language describes this behaviour as follows:

This is important: when $0 is changed by assignment or substitution, $1, $2, etc., and NF will be recomputed; likewise, when one of $1, $2, etc., is changed, $0 is reconstructed using OFS to separate fields.