Shell Programming and Scripting

fileA
HEADER LINE A
CommentLine A
Content A
....
....
....
TAILER A

fileB
HEADER LINE B
CommentLine B
Content B
....
....
....
TAILER B

HEADER LINE A
CommentLine A
Content A
....
....
....
Content B
....
....
....
TAILER B

        open ( FA, "$fileA" ) || die("can't open fileA $!");
        open ( FB, "$fileB" ) || die("can't open fileB $!");
        open ( TMP, ">> tmp_file" ) || die("can't open tmp_file $!");

        #reading both files in array
        my @fileA = <FA>;
        my @fileB = <FB>;

        #getting rid of HEADER, Comment line, in fileB
        shift @fileB;
        shift @fileB;

        #getting rid of TAILER in fileA
        pop @fileA;

        my @tmp_file=(@fileA,@fileB);

        foreach ( @tmp_file ){
            print TMP $_;
        }

        close(FA);
        close(FB);
        close(TMP);
        
        rename tmp_file, fileA || die("can't rename tmp_file to fileA);

open ( FA, "$fileA" ) || die("can't open fileA $!");
open ( FB, "$fileB" ) || die("can't open fileB $!");
open ( TMP, ">> tmp_file" ) || die("can't open tmp_file $!");


my $line;
foreach  (<FA>)  {
    #getting rid of TAILER in fileA
    print TMP $line if $line;
    $line = $_;
    }

$count = 0; 
foreach  (<FB>)  {
    #getting rid of HEADER, Comment line, in fileB
    next if ($++counter < 2) ;
    print TMP $_;
    }
}

close(FA);
close(FB);
close(TMP);
rename tmp_file, fileA || die("can't rename tmp_file to fileA);

my $line; 
foreach  (<FA>)  
{     #getting rid of TAILER in fileA     
         print TMP $line if $line;
         $line = $_;
}