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36 .\" @(#)scanf.3 8.2 (Berkeley) 12/11/93
37 .\" $FreeBSD: src/lib/libc/stdio/scanf.3,v 1.7.2.6 2002/04/12 16:34:38 trhodes Exp $
49 .Nd input format conversion
55 .Fn scanf "const char *format" ...
57 .Fn fscanf "FILE *stream" "const char *format" ...
59 .Fn sscanf "const char *str" "const char *format" ...
62 .Fn vscanf "const char *format" "va_list ap"
64 .Fn vsscanf "const char *str" "const char *format" "va_list ap"
66 .Fn vfscanf "FILE *stream" "const char *format" "va_list ap"
70 family of functions scans input according to a
73 This format may contain
74 .Em conversion specifiers ;
75 the results from such conversions, if any,
76 are stored through the
82 reads input from the standard input stream
85 reads input from the stream pointer
89 reads its input from the character string pointed to by
96 and reads input from the stream pointer
98 using a variable argument list of pointers (see
102 function scans a variable argument list from the standard input and
105 function scans it from a string;
106 these are analogous to
111 functions respectively.
114 argument must correspond properly with
115 each successive conversion specifier
119 All conversions are introduced by the
121 (percent sign) character.
125 may also contain other characters.
126 White space (such as blanks, tabs, or newlines) in the
128 string match any amount of white space, including none, in the input.
132 when an input character does not match such a format character.
134 when an input conversion cannot be made (see below).
138 character introducing a conversion
139 there may be a number of
141 characters, as follows:
142 .Bl -tag -width indent
144 Suppresses assignment.
145 The conversion that follows occurs as usual, but no pointer is used;
146 the result of the conversion is simply discarded.
148 Indicates that the conversion will be one of
152 and the next pointer is a pointer to a
157 Indicates either that the conversion will be one of
161 and the next pointer is a pointer to a
165 or that the conversion will be one of
167 and the next pointer is a pointer to
172 Indicates that the conversion will be
174 and the next pointer is a pointer to
176 (This type is not implemented; the
178 flag is currently ignored.)
180 Indicates either that the conversion will be one of
184 and the next pointer is a pointer to a
190 In addition to these flags,
191 there may be an optional maximum field width,
192 expressed as a decimal integer,
196 If no width is given,
197 a default of `infinity' is used (with one exception, below);
198 otherwise at most this many characters are scanned
199 in processing the conversion.
200 Before conversion begins,
201 most conversions skip white space;
202 this white space is not counted against the field width.
204 The following conversions are available:
207 Matches a literal `%'.
208 That is, `%\&%' in the format string
209 matches a single input `%' character.
210 No conversion is done, and assignment does not occur.
212 Matches an optionally signed decimal integer;
213 the next pointer must be a pointer to
218 this exists only for backwards compatibility.
220 Matches an optionally signed integer;
221 the next pointer must be a pointer to
223 The integer is read in base 16 if it begins
228 in base 8 if it begins with
230 and in base 10 otherwise.
231 Only characters that correspond to the base are used.
233 Matches an octal integer;
234 the next pointer must be a pointer to
239 this exists for backwards compatibility.
241 Matches an optionally signed decimal integer;
242 the next pointer must be a pointer to
245 Matches an optionally signed hexadecimal integer;
246 the next pointer must be a pointer to
253 but is backwards compatible with previous
257 Matches an optionally signed floating-point number;
258 the next pointer must be a pointer to
271 but is backwards compatible with previous
277 this exists only for backwards compatibility.
279 Matches a sequence of non-white-space characters;
280 the next pointer must be a pointer to
282 and the array must be large enough to accept all the sequence and the
286 The input string stops at white space
287 or at the maximum field width, whichever occurs first.
289 Matches a sequence of
292 characters (default 1);
293 the next pointer must be a pointer to
295 and there must be enough room for all the characters
299 The usual skip of leading white space is suppressed.
300 To skip white space first, use an explicit space in the format.
302 Matches a nonempty sequence of characters from the specified set
303 of accepted characters;
304 the next pointer must be a pointer to
306 and there must be enough room for all the characters in the string,
310 The usual skip of leading white space is suppressed.
311 The string is to be made up of characters in
314 the set is defined by the characters between the open bracket
323 if the first character after the open bracket is a circumflex
325 To include a close bracket in the set,
326 make it the first character after the open bracket
328 any other position will end the set.
332 when placed between two other characters,
333 it adds all intervening characters to the set.
335 make it the last character before the final close bracket.
338 means the set `everything except close bracket, zero through nine,
340 The string ends with the appearance of a character not in the
341 (or, with a circumflex, in) set
342 or when the field width runs out.
344 Matches a pointer value (as printed by
348 the next pointer must be a pointer to
352 instead, the number of characters consumed thus far from the input
353 is stored through the next pointer,
354 which must be a pointer to
358 a conversion, although it can be suppressed with the
363 For backwards compatibility,
364 other conversion characters (except
366 are taken as if they were
370 and a `conversion' of
372 causes an immediate return of
378 conversions will be changed in the future
382 after which they will act like
391 the number of input items assigned, which can be fewer than provided
392 for, or even zero, in the event of a matching failure.
394 indicates that, while there was input available,
395 no conversions were assigned;
396 typically this is due to an invalid input character,
397 such as an alphabetic character for a
402 is returned if an input failure occurs before any conversion such as an
404 If an error or end-of-file occurs after conversion
406 the number of conversions which were successfully completed is returned.
422 The current situation with
426 conversions is unfortunate.
428 All of the backwards compatibility formats will be removed in the future.
430 Numerical strings are truncated to 512 characters; for example,