0004594: scanf %s processing

Notes
(0004600) weis (developer) 2008-09-08 14:14	The behaviour you observed is conformant to the specification: %s: reads a string argument that spreads as much as possible, until the following bounding condition holds: a whitespace has been found, a scanning indication has been encountered, or the end-of-input has been reached. Hence, this conversion always succeeds: it returns an empty string if the bounding condition holds when the scan begins. The first scan returns "xxx" and ends on the space character. The second scan then starts on this space character; according to the specification, it stops immediately and returns an empty string. If you want to skip the space, you simply have to mention it in the format: if the first format is "%s " then the second scan starts after the space (alternatively, the second scan may be " %s" to skip the space before scanning the second string). Furthermore, as mentioned in the documentation, the usage of fscanf is kind of picky: To avoid confusion, consider using [bscanf] with an explicitly created scanning buffer. Use for instance [Scanning.from_file fname], to allocate the scanning buffer reading from file [fname] once and for all. Therefore, I would suggest you avoid using fscanf as much as possible and use bscanf instead (let ib = Scanf.Scanning.from_file "tst" ...). As you mentioned, Ocaml versions prior to 3.10 produced a different output; in fact, the scanner always skipped blanks after a %s specification; this was confusing in case of reading a file one line at a time, since reading the last field of a line would silently skip any amount of empty lines, thus preventing the detection and proper treatment of empty lines by the programmer.

(0004936) weis (developer) 2009-04-29 20:39	This is not a bug, but a better behaviour to properly handle end of file conditions and empty lines.

Issue History
Date Modified	Username	Field	Change
2008-08-05 16:32	smitley	New Issue
2008-08-05 16:41	xleroy	Status	new => assigned
2008-08-05 16:41	xleroy	Assigned To	=> weis
2008-09-08 14:14	weis	Note Added: 0004600
2008-09-08 14:37	weis	Status	assigned => resolved
2008-09-08 14:37	weis	Resolution	open => fixed
2009-04-29 20:39	weis	Note Added: 0004936
2009-04-29 20:39	weis	Status	resolved => closed
2009-04-29 20:39	weis	Fixed in Version	=> 3.10.0
2012-02-02 15:19	protz	Category	Caml-light => Caml light

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