SCANF(3S)                            BSD                             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:

     ⊕  Blanks, tabs, or newlines, which match optional white space in the
        input.

     ⊕  An ordinary character (not %) which must match the next character of
        the input stream.

     ⊕  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 non-space 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.
     The following conversion characters are legal:

     %  a single "%" is expected in the input at this point; no assignment is
        done.

     d  A decimal integer is expected; the corresponding argument should be an
        integer pointer.

     o  An octal integer is expected; the corresponding argument should be a
        integer pointer.

     x  A hexadecimal integer is expected; the corresponding argument should
        be an 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.

     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 non-space 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.

     e  A floating-point number is expected; the next field is converted
     f  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.

     [  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 circumflex (^), 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.  If there
        are two sequential delimiters in the input field, the remainder of the
        pattern is not matched and the remaining fields will be returned as
        zero or null.  The corresponding argument must point to a character
        array.

     The conversion characters d, o, and x can be capitalized or preceded by l
     (el) to indicate that a pointer to long rather than to int is in the
     argument list.  Similarly, the 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 can be preceded 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.

     For example, the call

               int i; float x; char name[50];
               scanf("%d%f%s", &i, &x, name);

     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."  Or,

          int i; float x; char name[50];
          scanf("%2d%f%*d%[1234567890]", &i, &x, name);

     with input

          56789 0123 56a72

     will assign 56 to i, 789.0 to x, skip "0123," and place the string "56\0"

     in name.  The next call to getchar will return "a".

SEE ALSO
     atof(3), getc(3S), printf(3S)

DIAGNOSTICS
     The scanf functions return EOF on end of input, and a short count for
     missing or illegal data items.

BUGS
     The success of literal matches and suppressed assignments is not directly
     determinable.