SCANF(3S) COMMAND REFERENCE SCANF(3S) NAME scanf, fscanf, sscanf - formatted input conversion SYNOPSIS #include <stdio.h> scanf(format [ , pointer ] . . ) char *format; fscanf(stream, format [ , pointer ] . . ) FILE *stream; char *format; sscanf(s, format [ , pointer ] . . ) char *s, *format; DESCRIPTION Scanf reads from the standard input stream stdin. Fscanf reads from the named input stream. Sscanf reads from the character string s. Each function reads characters, interprets them according to a format, and stores the results in its arguments. Each expects as arguments a control string format, described below, and a set of pointer arguments indicating where the converted input should be stored. The control string usually contains conversion specifications, which are used to direct interpretation of input sequences. The control string may contain: 1. Blanks, tabs or newlines, which match optional white space in the input. 2. An ordinary character (not %) which must match the next character of the input stream. 3. Conversion specifications, consisting of the character %, an optional assignment suppressing character *, an optional numerical maximum field width, and a conversion character. A conversion specification directs the conversion of the next input field; the result is placed in the variable pointed to by the corresponding argument, unless assignment suppression was indicated by *. An input field is defined as a string of nonspace characters; it extends to the next inappropriate character or until the field width, if specified, is exhausted. The conversion character indicates the interpretation of the input field; the corresponding pointer argument must usually be of a restricted type. These conversion characters are Printed 5/12/88 1
SCANF(3S) COMMAND REFERENCE SCANF(3S) legal: c A character is expected; the corresponding argument should be a character pointer. The normal skip-over space characters is suppressed in this case; to read the next nonspace character, try %1s. If a field width is given, the corresponding argument should refer to a character array, and the indicated number of characters is read. d A decimal integer is expected; the corresponding argument should be an integer pointer. e A floating point number is expected; the next field is f converted accordingly and stored through the corresponding argument, which should be a pointer to a float. The input format for floating point numbers is an optionally signed string of digits possibly containing a decimal point, followed by an optional exponent field consisting of an E or e followed by an optionally signed integer. o An octal integer is expected; the corresponding argument should be a integer pointer. s A character string is expected; the corresponding argument should be a character pointer pointing to an array of characters large enough to accept the string and a terminating \0, which will be added. The input field is terminated by a space character or a newline. x Hexadecimal integer is expected; corresponding argument should be an integer pointer. % A single % is expected in the input at this point; no assignment is done. [ Indicates a string not to be delimited by space characters. The left bracket is followed by a set of characters and a right bracket; the characters between the brackets define a set of characters making up the string. If the first character is not a caret (^), the input field is all characters until the first character not in the set between the brackets; if the first character after the left bracket is ^, the input field is all characters until the first character which is in the remaining set of characters between the brackets. The corresponding argument must point to a character array. The conversion characters d, o, and x may be capitalized or preceeded by l to indicate that a pointer to long rather than to int is in the argument list. Similarly, the Printed 5/12/88 2
SCANF(3S) COMMAND REFERENCE SCANF(3S) conversion characters e or f may be capitalized or preceded by l to indicate a pointer to double rather than to float. The conversion characters d, o, and x may be preceeded by h to indicate a pointer to short rather than to int. The scanf functions return the number of successfully matched and assigned input items. This can be used to decide how many input items were found. The constant EOF is returned upon end of input; note that this is different from 0, which means that no conversion was done; if conversion was intended, it was frustrated by an inappropriate character in the input. EXAMPLES The following call with the input line 25 54.32E-1 thompson will assign to i the value 25, x the value 5.432, and name will contain `thompson\0': int i; float x; char name[50]; scanf("%d %f %s", &i, &x, name); In the next example, the input 56789 0123 56a72 will assign 56 to i, 789.0 to x, skip 0123, and place the string 56\0 in name. int i; float x; char name[50]; scanf("%2d %f %*d %[1234567890]", &i, &x, name); After this, the next call to getchar will return a. DIAGNOSTICS Scanf functions return EOF on end of input and a short count for missing or illegal data items. CAVEATS The success of literal matches and suppressed assignments is not directly determinable. SEE ALSO atof(3c), getc(3s), and printf(3s). Printed 5/12/88 3
%%index%% na:288,102; sy:390,1867; de:2257,2002;4619,2752;7731,992; ex:8723,881; di:9604,309; ca:9913,177; se:10090,166; %%index%%000000000144