Editing Printf (section)

===Width field===

The width field specifies the {{em|minimum}} number of characters to output. If the value can be represented in fewer characters, then the value is left-padded with spaces so that output is the number of characters specified. If the value requires more characters, then the output is longer than the specified width. A value is never truncated.

For example, {{code|printf("%3d", 12);|c}} specifies a width of 3 and outputs {{samp|12}} with a space on the left to output 3 characters. The call {{code|printf("%3d", 1234);|c}} outputs {{samp|1234}} which is 4 characters long since that is the minimum width for that value even though the width specified is 3.

If the width field is omitted, the output is the minimum number of characters for the value.

If the field is specified as {{code|*}}, then the width value is read from the list of values in the call.<ref>{{cite web |title=printf |url=http://www.cplusplus.com/reference/cstdio/printf/ |access-date=2020-06-10 |website=cplusplus.com}}</ref> For example, {{code|printf("%*d", 3, 10);|c}} outputs <samp style="white-space:pre"> 10</samp> where the second parameter, {{code|3|c}}, is the width (matches with {{code|*}}) and {{code|10|c}} is the value to [[serialization|serialize]] (matches with {{code|d}}).

Though not part of the width field, a leading zero is interpreted as the zero-padding flag mentioned above, and a negative value is treated as the positive value in conjunction with the left-alignment {{code|-}} flag also mentioned above.

The width field can be used to format values as a table (tabulated output). But, columns do not align if any value is larger than fits in the width specified. For example, notice that the last line value ({{samp|1234}}) does not fit in the first column of width 3 and therefore the column is not aligned.

<syntaxhighlight lang="output">
  1   1
 12  12
123 123
1234 123
</syntaxhighlight>