2.11BSD#431 - /usr/man/cat3/scanf.0

SCANF(3S)	    UNIX Programmer's Manual		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
     be of a restricted type.  The following conversion charac-
     ters are legal:


Printed 11/26/99	  May 15, 1985				1


SCANF(3S)	    UNIX Programmer's Manual		SCANF(3S)


     %	 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
	  f
	       a floating point number is expected; the next field is
	 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
     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


Printed 11/26/99	  May 15, 1985				2


SCANF(3S)	    UNIX Programmer's Manual		SCANF(3S)


     conversion characters d, o and x may 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 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(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.


Printed 11/26/99	  May 15, 1985				3