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1.1 root 1: .\" @(#)scanf.3 6.2 (Berkeley) 4/1/89
2: .\"
3: .TH SCANF 3 "April 1, 1989"
4: .AT 3
5: .SH NAME
6: scanf, fscanf, sscanf \- formatted input conversion
7: .SH SYNOPSIS
8: .B #include <stdio.h>
9: .PP
10: .B scanf(format
11: [ , pointer ] . . .
12: .B )
13: .br
14: .B char *format;
15: .PP
16: .B fscanf(stream, format
17: [ , pointer ] . . .
18: .B )
19: .br
20: .SM
21: .B FILE
22: .B *stream;
23: .br
24: .B char *format;
25: .PP
26: .B sscanf(s, format
27: [ , pointer ] . . .
28: .B )
29: .br
30: .B char *s, *format;
31: .SH DESCRIPTION
32: .I Scanf
33: reads from the standard input stream
34: .BR stdin .
35: .I Fscanf
36: reads from the named input
37: .IR stream .
38: .I Sscanf
39: reads from the character string
40: .IR s .
41: Each function reads characters, interprets
42: them according to a format, and stores the results in its arguments.
43: Each expects as arguments
44: a control string
45: .IR format ,
46: described below,
47: and a set of
48: .I pointer
49: arguments
50: indicating where the converted input should be stored.
51: .PP
52: The
53: control string
54: usually contains
55: conversion specifications, which are used to direct interpretation
56: of input sequences.
57: The control string may contain:
58: .TP 4
59: 1.
60: Blanks, tabs or newlines,
61: which match optional white space in the input.
62: .TP 4
63: 2.
64: An ordinary character (not %) which must match
65: the next character of the input stream.
66: .TP 4
67: 3.
68: Conversion specifications, consisting of the
69: character
70: .BR % ,
71: an optional assignment suppressing character
72: .BR * ,
73: an optional numerical maximum field width, and a conversion
74: character.
75: .PP
76: A conversion specification directs the conversion of the
77: next input field; the result
78: is placed in the variable pointed to by the corresponding argument,
79: unless assignment suppression was
80: indicated by
81: .BR * .
82: An input field is defined as a string of non-space characters;
83: it extends to the next inappropriate character or until the field
84: width, if specified, is exhausted.
85: .PP
86: The conversion character indicates the interpretation of the
87: input field; the corresponding pointer argument must
88: usually be of a restricted type.
89: The following conversion characters are legal:
90: .TP 4
91: .B %
92: a single `%' is expected
93: in the input at this point;
94: no assignment is done.
95: .TP 4
96: .B d
97: a decimal integer is expected;
98: the corresponding argument should be an integer pointer.
99: .TP 4
100: .B o
101: an octal integer is expected;
102: the corresponding argument should be a integer pointer.
103: .TP 4
104: .B x
105: a hexadecimal integer is expected;
106: the corresponding argument should be an integer pointer.
107: .ti -0.2i
108: .TP 4
109: .B s
110: a character string is expected;
111: the corresponding argument should be a character pointer
112: pointing to an array of characters large enough to accept the
113: string and a terminating `\e0', which will be added.
114: The input field is terminated by a space character
115: or a newline.
116: .TP 4
117: .B c
118: a character is expected; the
119: corresponding argument should be a character pointer.
120: The normal skip over space characters is suppressed
121: in this case;
122: to read the next non-space character, try
123: `%1s'.
124: If a field width is given, the corresponding argument
125: should refer to a character array, and the
126: indicated number of characters is read.
127: .TP 4
128: \z\fBe\v'1'f\v'-1'\fR
129: a
130: floating point number is expected;
131: the next field is converted accordingly and stored through the
132: corresponding argument, which should be a pointer to a
133: .IR float .
134: The input format for
135: floating point numbers is
136: an optionally signed
137: string of digits
138: possibly containing a decimal point, followed by an optional
139: exponent field consisting of an E or e followed by an optionally signed integer.
140: .TP 4
141: .B [
142: indicates a string not to be delimited by space characters.
143: The left bracket is followed by a set of characters and a right
144: bracket; the characters between the brackets define a set
145: of characters making up the string.
146: If the first character
147: is not circumflex (\|^\|), the input field
148: is all characters until the first character not in the set between
149: the brackets; if the first character
150: after the left bracket is ^, the input field is all characters
151: until the first character which is in the remaining set of characters
152: between the brackets.
153: The corresponding argument must point to a character array.
154: .PP
155: The conversion characters
156: .BR d ,
157: .B o
158: and
159: .B x
160: may be capitalized or preceded by
161: .B l
162: to indicate that a pointer to
163: .B long
164: rather than to
165: .B int
166: is in the argument list.
167: Similarly, the conversion characters
168: .B e
169: or
170: .B f
171: may be capitalized or
172: preceded by
173: .B l
174: to indicate a pointer to
175: .B double
176: rather than to
177: .BR float .
178: The conversion characters
179: .BR d ,
180: .B o
181: and
182: .B x
183: may be preceded by
184: .B h
185: to indicate a pointer to
186: .B short
187: rather than to
188: .BR int .
189: .PP
190: The
191: .I scanf
192: functions return the number of successfully matched and assigned input
193: items.
194: This can be used to decide how many input items were found.
195: The constant
196: .SM
197: .B EOF
198: is returned upon end of input; note that this is different
199: from 0, which means that no conversion was done;
200: if conversion was intended, it was frustrated by an
201: inappropriate character in the input.
202: .PP
203: For example, the call
204: .IP "" 10
205: int i; float x; char name[50];
206: .br
207: scanf("%d%f%s", &i, &x, name);
208: .PP
209: with the input line
210: .IP
211: 25 54.32E\(mi1 thompson
212: .PP
213: will assign to
214: .I i
215: the value
216: 25,
217: .I x
218: the value 5.432, and
219: .I name
220: will contain
221: .IR `thompson\e0' .
222: Or,
223: .IP
224: int i; float x; char name[50];
225: .br
226: scanf("%2d%f%*d%[1234567890]", &i, &x, name);
227: .PP
228: with input
229: .IP
230: 56789 0123 56a72
231: .PP
232: will assign 56 to
233: .IR i ,
234: 789.0 to
235: .IR x ,
236: skip `0123',
237: and place the string `56\e0' in
238: .IR name .
239: The next call to
240: .I getchar
241: will return `a'.
242: .SH "SEE ALSO"
243: atof(3),
244: getc(3),
245: printf(3)
246: .SH DIAGNOSTICS
247: The
248: .I scanf
249: functions return
250: .SM
251: .B EOF
252: on end of input,
253: and a short count for missing or illegal data items.
254: .SH BUGS
255: The success of literal matches and suppressed
256: assignments is not directly
257: determinable.
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