1SCANF(3S) SCANF(3S)
2
6 scanf, fscanf, sscanf - formatted input conversion
7
9 #include <stdio.h>
10 scanf(format [ , pointer ] . . . )
12 char *format;
13 fscanf(stream, format [ , pointer ] . . . )
15 FILE *stream;
16 char *format;
17 sscanf(s, format [ , pointer ] . . . )
19 char *s, *format;
20
22 Scanf reads from the standard input stream stdin. Fscanf reads from
23 the named input stream. Sscanf reads from the character string s.
24 Each function reads characters, interprets them according to a format,
25 and stores the results in its arguments. Each expects as arguments a
26 control string format, described below, and a set of pointer arguments
27 indicating where the converted input should be stored.
28 The control string usually contains conversion specifications, which
30 are used to direct interpretation of input sequences. The control
31 string may contain:
32 1. Blanks, tabs or newlines, which match optional white space in the
34 input.
35 2. An ordinary character (not %) which must match the next character
37 of the input stream.
38 3. Conversion specifications, consisting of the character %, an
40 optional assignment suppressing character *, an optional numerical
41 maximum field width, and a conversion character.
42 A conversion specification directs the conversion of the next input
44 field; the result is placed in the variable pointed to by the corre‐
45 sponding argument, unless assignment suppression was indicated by *.
46 An input field is defined as a string of non-space characters; it
47 extends to the next inappropriate character or until the field width,
48 if specified, is exhausted.
49 The conversion character indicates the interpretation of the input
51 field; the corresponding pointer argument must usually be of a
52 restricted type. The following conversion characters are legal:
53 % a single `%' is expected in the input at this point; no assignment
55 is done.
56 d a decimal integer is expected; the corresponding argument should be
58 an integer pointer.
59 o an octal integer is expected; the corresponding argument should be
61 a integer pointer.
62 x a hexadecimal integer is expected; the corresponding argument
64 should be an integer pointer.
65 s a character string is expected; the corresponding argument should
67 be a character pointer pointing to an array of characters large
68 enough to accept the string and a terminating `\0', which will be
69 added. The input field is terminated by a space character or a
70 newline.
71 c a character is expected; the corresponding argument should be a
73 character pointer. The normal skip over space characters is sup‐
74 pressed in this case; to read the next non-space character, try
75 `%1s'. If a field width is given, the corresponding argument
76 should refer to a character array, and the indicated number of
77 characters is read.
78 e a floating point number is expected; the next field is converted
80 f accordingly and stored through the corresponding argument, which
81 should be a pointer to a float. The input format for floating
82 point numbers is an optionally signed string of digits possibly
83 containing a decimal point, followed by an optional exponent field
84 consisting of an E or e followed by an optionally signed integer.
85 [ indicates a string not to be delimited by space characters. The
87 left bracket is followed by a set of characters and a right
88 bracket; the characters between the brackets define a set of char‐
89 acters making up the string. If the first character is not circum‐
90 flex (^), the input field is all characters until the first charac‐
91 ter not in the set between the brackets; if the first character
92 after the left bracket is ^, the input field is all characters
93 until the first character which is in the remaining set of charac‐
94 ters between the brackets. The corresponding argument must point
95 to a character array.
96 The conversion characters d, o and x may be capitalized or preceded by
98 l to indicate that a pointer to long rather than to int is in the argu‐
99 ment list. Similarly, the conversion characters e or f may be capital‐
100 ized or preceded by l to indicate a pointer to double rather than to
101 float. The conversion characters d, o and x may be preceded by h to
102 indicate a pointer to short rather than to int.
103 The scanf functions return the number of successfully matched and
105 assigned input items. This can be used to decide how many input items
106 were found. The constant EOF is returned upon end of input; note that
107 this is different from 0, which means that no conversion was done; if
108 conversion was intended, it was frustrated by an inappropriate charac‐
109 ter in the input.
110 For example, the call
112 int i; float x; char name[50];
114 scanf("%d%f%s", &i, &x, name);
115 with the input line
117 25 54.32E−1 thompson
119 will assign to i the value 25, x the value 5.432, and name will contain
121 `thompson\0'. Or,
122 int i; float x; char name[50];
124 scanf("%2d%f%*d%[1234567890]", &i, &x, name);
125 with input
127 56789 0123 56a72
129 will assign 56 to i, 789.0 to x, skip `0123', and place the string
131 `56\0' in name. The next call to getchar will return `a'.
132
134 atof(3), getc(3S), printf(3S)
135
137 The scanf functions return EOF on end of input, and a short count for
138 missing or illegal data items.
139
141 The success of literal matches and suppressed assignments is not
142 directly determinable.
1437th Edition May 15, 1985 SCANF(3S)