Shell Programming and Scripting

ZZZZ
AAA
DDDD

open (FILE,"+>>C:\\Documents and Settings\\trial.txt\n")|| die "can't open file"; 
while(<FILE>) 
{         
    if(/AAA/) 
   { 
     print FILE "CCC\n";  
    } 
}#end while 
close(FILE);

ZZZZ
AAA
DDDD
ZZZZ
AAA
CCC

ZZZZ
AAA
CCC
DDDD

#!/usr/bin/perl
open(FILE,"foo.txt") || die "can't open file for read\n"; 
my @lines=<FILE>;
close(FILE);
open(FILE,">foo.txt")|| die "can't open file for write\n";
foreach $line (@lines) {
    if($line =~ /AAA/) {
        print FILE "CCC\n";
    } else {
        print FILE $line;
    }
}#end foreach
close(FILE);

#!/usr/bin/perl
open(FILE,"foo.txt") || die "can't open file for read\n"; 
my @lines=<FILE>;
close(FILE);
open(FILE,">foo.txt")|| die "can't open file for write\n";
foreach $line (@lines) {
    print FILE "CCC\n" if($line =~ /AAA/);
    print FILE $line;
}#end foreach
close(FILE);

    print FILE "CCC\n" if($line =~ /AAA/);
    print FILE $line;

#!/usr/bin/perl -w
open(IFILE,"<test.abc") || die "can't open file for read\n"; 
open(OFILE,">abc.out") || die "can't open file for writing\n"; 
while (<IFILE>){
     if(/AAA/) {
        print OFILE $_;
        print OFILE "CCC\n";
    }else {
        print OFILE $_;
}
}
close(IFILE);
close(OFILE);

$ cat test.abc 
ZZZZ
AAA
DDDD
$ cat abc.out 
ZZZZ
AAA
CCC
DDDD