Overwriting Records

• Suppose we are replacing a record with another of exactly the same length

• Then we need not rewrite the entire file

• For example:

        sub uppercase_username {
          my ($fh, $username) = @_;
          seek $fh, 0, SEEK_SET;
          while (<$fh>) {
            my ($u, $rest) = split /:/, $_, 2;
            next unless $u eq $username;
            seek $fh, -length($_), SEEK_CUR;
            print $fh uc($u);
            return;
          }
        }

• We search the file as usual

• When we find the record we want, we back up and overwrite it in place

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Copyright © 2003 M. J. Dominus