SCANF(3S)                                               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, inter-
          prets 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 specifica-
          tions, 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 non-space characters; it extends to the next
          inappropriate character or until the field width, if speci-
          fied, is exhausted.

          The conversion character indicates the interpretation of the
          input field; the corresponding pointer argument must usually

     SCANF(3S)                                               SCANF(3S)

          be of a restricted type.  The following conversion charac-
          ters are legal:

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

          d   a decimal integer is expected; the corresponding argu-
              ment 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 argu-
              ment 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
          f   converted accordingly and stored through the correspond-
              ing 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 charac-
              ters.  The left bracket is followed by a set of charac-
              ters 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 char-
              acter 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
          preceded by l to indicate that a pointer to long rather than

     SCANF(3S)                                               SCANF(3S)

          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 con-
          version characters d, o and x may be preceded by h to indi-
          cate 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 charac-
          ter 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(3), printf(3)

     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.