Issue 0061: Interpretation of white space in the format string of a scan statement

This issue has been automatically converted from the original issue lists and some formatting may not have been preserved.

Authors: Ed Bendickson, X3 Secretariat (USA)
Date: 1993-08-19
Submitted against: C90
Status: Closed
Converted from: dr.htm, dr_061.html

I am requesting an interpretation of white space in the format string of a scan statement. One of our customers is concerned about this as it appears to conflict with some books on C. I am referring to subclause 7.9.6.2, page 135, paragraph 3:

A directive composed of white space character(s) is executed by reading input up to the first non-white-space character (which remains unread), or until no more characters can be read.

Page 135, paragraph 7 says:

If the length of the input item is zero, the execution of the directive fails: this condition is a matching failure, unless an error prevented input from the stream, in which case it is an input failure.

My questions are:

1. Is white space in the format string a directive which must be satisfied by white space in the input string?
2. What are the correct answers to the following examples? Note the white space in the format string.

Example 1:

inputString = "123ABCD";
 numAssigned = sscanf(inputString, "%lu %ls", &ulongVal, junkchar);

Should the result be numAssigned equal to 1?

Example 2:

inputString = "123ABCD";
 numAssigned = sscanf(inputString, "%lu%ls", &ulongVal, junkchar);

Should the result be numAssigned equal to 2?

Comment from WG14 on 1997-09-23:

Response

A directive composed of one or more white-space characters can successfully match zero white-space characters in the input stream. The paragraphs that intervene between your two quotations make clear that the second paragraph applies only to a directive that is a conversion specification.

Thus, both examples should assign 2 to numAssigned.