FAQ 4.33 How do I pad a string with blanks or pad a number with zeroes?

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4.33: How do I pad a string with blanks or pad a number with zeroes?

    In the following examples, $pad_len is the length to which you wish to
    pad the string, $text or $num contains the string to be padded, and
    $pad_char contains the padding character. You can use a single character
    string constant instead of the $pad_char variable if you know what it is
    in advance. And in the same way you can use an integer in place of
    $pad_len if you know the pad length in advance.

    The simplest method uses the "sprintf" function. It can pad on the left
    or right with blanks and on the left with zeroes and it will not
    truncate the result. The "pack" function can only pad strings on the
    right with blanks and it will truncate the result to a maximum length of

        # Left padding a string with blanks (no truncation):
            $padded = sprintf("%$s", $text);
            $padded = sprintf("%*s", $pad_len, $text);  # same thing

        # Right padding a string with blanks (no truncation):
            $padded = sprintf("%-$s", $text);
            $padded = sprintf("%-*s", $pad_len, $text); # same thing

        # Left padding a number with 0 (no truncation):
            $padded = sprintf("%0$d", $num);
            $padded = sprintf("%0*d", $pad_len, $num); # same thing

        # Right padding a string with blanks using pack (will truncate):
        $padded = pack("A$pad_len",$text);

    If you need to pad with a character other than blank or zero you can use
    one of the following methods. They all generate a pad string with the
    "x" operator and combine that with $text. These methods do not truncate

    Left and right padding with any character, creating a new string:

        $padded = $pad_char x ( $pad_len - length( $text ) ) . $text;
        $padded = $text . $pad_char x ( $pad_len - length( $text ) );

    Left and right padding with any character, modifying $text directly:

        substr( $text, 0, 0 ) = $pad_char x ( $pad_len - length( $text ) );
        $text .= $pad_char x ( $pad_len - length( $text ) );


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