Add automatic header comments for all source files - bash

Question

I have a standardized way of writing comments before and after a function.
For example before declaring any function I write,
!---------------------------
! NAME_OF_FUNC (no)
!---------------------------
where no is the nth function in a given file containing multiple functions.
I know that a function e.g begins with (Fortran convention) either subroutine NAME_OF_SUB or function NAME_OF_FUNC. Hence, my end result would be
!---------------------------
! NAME_OF_FUNC (no)
!---------------------------
function NAME_OF_FUNC(...)
end function
!---------------------------
Can somebody show an example of how to write a bash script or in any other scripting language a code that can go through all my source files and the standard convention I just showed an example of?

Answer 1

Here is an example in Perl. It does not take backup before overwriting (I would recommend that you try to improve this script and add backup functionality). It also does not add the end of subroutine marker. But it would easy to add that functionality, please try. It also assumes that you want to modify all *.f95 files in the current directory and all its sub directories:
use feature qw(say state);
use strict;
use warnings;
use File::Find::Rule;
my #files = File::Find::Rule->new->name('*.f95')->in('.');
for my $fn (#files) {
open ( my $fh, '<', $fn ) or die "Could not open file '$fn': $!";
my $txt = do {local $/; <$fh>};
close $fh;
process_txt( \$txt );
save_txt( $fn, \$txt );
}
sub save_txt {
my ( $fn, $txt ) = #_;
open ( my $fh, '>', $fn ) or die "Could not open file '$fn': $!";
print $fh $$txt;
close $fh;
}
sub process_txt {
my ( $txt ) = #_;
my $i = 1;
$$txt =~ s/^(.*(?i:function|subroutine)\s+)([a-zA-Z_]+)(\s*\(.*$)/
do_substitution($1, $2, $3, $i++)/egmx;
}
sub do_substitution {
my ( $head, $name, $end, $i ) = #_;
my $line = $head . $name . $end;
$line =~ s/\s+$//;
my $N = length $line;
my $cline = '!' . '-' x $N;
my $mline = '! ' . $name;
my $snum = "($i)";
my $M = (length $mline) + (length $snum);
my $mspc = ($N > $M) ? (' ' x ($N-$M)) : ' ';
$mline = $mline . $mspc . $snum;
my $new_txt = join "\n", $cline, $mline, $cline, $line;
return $new_txt;
}