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fscanf

Usage

   #include <stdio.h>
   int fscanf(FILE *fp,const char *format,...);

   ANSI

Description

   Reads characters from the input stream fp. Characters read are converted
   according to the format string and the values created are stored through
   the argument pointers.

   Note that the arguments are pointers to where values are to be stored.

   The format string consists of:

   1. Spaces, tabs and newlines which cause input to be skipped up to the
   next character which is not a whitespace.


   2. Other characters, except for % which are matched against the input.

   3. A conversion specification, which is as follows:

       '%' ['*'] [field-width] [precision] conv_char

   This specifies how input characters are to be converted and assigned
   through the corresponding argument pointers. Conversion continues until a
   conflicting input character is encountered or the field_width is reached.

   *  is an assignment suppression flag. It causes the conversion to be
   performed but the result is ignored. There is no corresponding argument
   pointer for this.

   If there are less argument pointers than conversion specification the
   results are unpredictable. If there are extra argument pointers the
   excess ones are ignored.

   field_width is a sequence of decimal digits specifying the maximum number
   of characters in the field.

   precision

   L, l     If l is used with one of the (b, d, i, o, u, or x)
            conversion characters, then it indicates that the
            argument is a pointer to a long rather than a pointer to
            an int. The l or L flag, when used with the e or f
            conversion character, means that the argument is a
            pointer to a double rather than a pointer to a float.

   h        Argument is a pointer to a short. Conversion Characters:
            conv_char The conversion characters are:

   b        A binary number is expected, the argument pointer must be
            a pointer to an int.

   d        An integer is expected, the argument pointer must be a
            pointer to an int. e, E, f, g, GA floating point
            number is expected. The format of the number is the same
            as in C. The argument pointer must be a pointer to a

            float (double if l or L is used).

   i        An integer is expected. If it starts with a 0, it is taken
            to be octal. If it starts with 0x or 0X, it is
            hexadecimal. The argument pointer must be a pointer to
            an int.

   o        An octal number is expected. The argument pointer must be
            a pointer to an int.

   p        A hexadecimal integer is expected. The argument pointer
            must be a pointer to a pointer.

   u        An unsigned integer is expected, the argument pointer must
            be a pointer to an unsigned.

   n        Through the argument pointer is stored an integer
            specifying the number of characters read up to this
            point by this call to fscanf.


   [        A string is expected. Between the [ and a closing ] will
            be the characters acceptable to the string. If the [ is
            immediately followed by a , the acceptable characters for
            the string are all those except the ones between the  and
            the ] . The argument pointer must be a pointer to a
            string. A 0 is appended to the string.

   s        A string is expected. The argument pointer must be a
            pointer to a string. The input field extends until a
            space or newline is read, which is not part of the
            field. A 0 is appended to the string.

   c        A character is expected. The argument pointer must be a
            pointer to a character. If a field_width is specified,
            then that many characters are read and the argument
            pointer must point to a character array large enough to
            hold the result.

   %        Match the input with a %.


   The conversion characters e, g and x may be in capitals, with no
   difference in meaning. Other conversion characters will cause unexpected
   results. Conflicting characters are left unread in the input stream.
   There is no direct way to determine if suppressed assignments or literal
   matches succeeded, unless %n is used.

Example 

   #include <stdio.h>

   char fst[10], *lst = "     ";
   int ttl;

   int main()
   {
       int rt;
       rt = fscanf(stdin, "%s %s %d",fst,lst,&ttl);
       printf("Values read %s %s %d\n",fst,lst,ttl);
       return rt == 3;
   }

Return Value

   The number of assigned input items excluding any assignment suppressed
   conversions is returned. If the end of file is encountered before any
   assignments are done or before any conflicts occur, an EOF is returned.
   fscanf() normally returns when it reaches the end of the format string.

See Also

   printf scanf sscanf fgets