Can anyone please explain this perl behavior that i came across?
printf("%what_the\n");
printf("\%what_the\n");
Prints:
%what_the
%what_the
WHILE...
printf("%tomorrow\n");
printf("\%tomorrow\n");
Prints:
0morrow
0morrow
...EVEN WITH warnings and strict:
use strict;
use warnings;
printf("\%tomorrow\n");
Prints:
Missing argument in printf at - line 3.
0morrow
printf is different from regular print. You might be thinking it is the same, it is not. printf takes a pattern, which includes %. For example:
printf "%s\n", "tomorrow"; # prints "tomorrow\n"
%s is a placeholder for a string, which should be the second argument to printf.
The warning you get shows you the problem
Missing argument in printf at - line 3.
printf expects a second argument, because you have supplied a placeholder.
Not all letters following a percent sign is a valid combination, here's a few from the documentation from sprintf
%% a percent sign
%c a character with the given number
%s a string
%d a signed integer, in decimal
%u an unsigned integer, in decimal
%o an unsigned integer, in octal
%x an unsigned integer, in hexadecimal
%e a floating-point number, in scientific notation
%f a floating-point number, in fixed decimal notation
%g a floating-point number, in %e or %f notation
.... more
I do not see %to in there, but it seems to be what is being triggered. It prints a 0 because it casts the empty string (missing argument) to 0.
Documentation here.
The way to escape a % sign is to double it, not by a backslash. %o is the format for printing an octal number. Try doing printf "%tomorrow", 255;. The t is a modifier flag on %o to set the integer type.
https://perldoc.perl.org/functions/sprintf#size
HTH