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SCANF(3V)                                                            SCANF(3V)



NAME
       scanf, fscanf, sscanf - formatted input conversion

SYNOPSIS
       #include <&lt;stdio.h>&gt;

       int scanf(format  [ , pointer... ] )
       char *format;

       int fscanf(stream, format  [ , pointer... ] )
       FILE *stream;
       char *format;

       int sscanf(s, format  [ , pointer... ] )
       char *s, *format;

SYSTEM V SYNOPSIS
       The following are provided for XPG2 compatibility:

       #define   nl_scanf  scanf
       #define   nl_fscanf fscanf
       #define   nl_sscanf sscanf

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 for-
       mat, and stores the results in its arguments.  Each expects,  as  argu-
       ments,  a  control string format, described below, and a set of pointer
       arguments indicating where the converted input should be  stored.   The
       results  are  undefined  in there are insufficient args for the format.
       If the format is exhausted while args remain, the excess args are  sim-
       ply ignored.

       The  control  string  usually contains conversion specifications, which
       are used to direct interpretation  of  input  sequences.   The  control
       string may contain:

              o  White-space characters (SPACE, TAB, or NEWLINE) which, except
                 in two cases described below, cause input to be  read  up  to
                 the next non-white-space character.
              o  An  ordinary  character  (not `%'), which must match the next
                 character of the input stream.
              o  Conversion specifications, consisting of the character `%' or
                 the  character  sequence %digit$, an optional assignment sup-
                 pressing character `*', an optional numerical  maximum  field
                 width,  an  optional  l (ell) or h indicating the size of the
                 receiving variable, and a conversion code.

       Conversion specifications are introduced by  the  character  %  or  the
       character  sequence  %digit$.   A  conversion specification directs the
       conversion of the next input field; the result is placed in  the  vari-
       able  pointed  to by the corresponding argument, unless assignment sup-
       pression was indicated by `*'.  The suppression of assignment  provides
       a  way  of  describing an input field which is to be skipped.  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.  For all descriptors except ``[''  and  ``c'',  white  space
       leading an input field is ignored.

       The  conversion  character  indicates  the  interpretation of the input
       field;  the  corresponding  pointer  argument  must  usually  be  of  a
       restricted type.  For a suppressed field, no pointer argument is given.
       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.
              u      An unsigned decimal integer is expected; the  correspond-
                     ing argument should be an unsigned integer pointer.
              o      An  octal integer is expected; the corresponding argument
                     should be an integer pointer.
              x      A hexadecimal  integer  is  expected;  the  corresponding
                     argument should be an integer pointer.
              i      An integer is expected; the corresponding argument should
                     be an integer pointer.  It will store the  value  of  the
                     next input item interpreted according to C conventions: a
                     leading ``0'' implies octal;  a  leading  ``0x''  implies
                     hexadecimal; otherwise, decimal.
              n      Stores in an integer argument the total number of charac-
                     ters (including white space) that have  been  scanned  so
                     far since the function call. No input is consumed.
              e,f,g  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  as  described
                     for string_to_decimal(3), with fortran_conventions zero.
              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  automatically.   The
                     input field is terminated by a white space character.
              c      A  character  is  expected;  the  corresponding  argument
                     should be a character  pointer.   The  normal  skip  over
                     white  space is suppressed in this case; to read the next
                     non-space character, use %1s.  If a field width is given,
                     the  corresponding  argument  should refer to a character
                     array, and the indicated number of characters is read.
              [      Indicates string data; the normal skip over leading white
                     space  is  suppressed.  The left bracket is followed by a
                     set of characters, which we will call the scanset, and  a
                     right bracket; the input field is the maximal sequence of
                     input characters consisting entirely of characters in the
                     scanset.   The  circumflex  (^),  when  it appears as the
                     first character in the scanset, serves  as  a  complement
                     operator  and  redefines  the  scanset  as the set of all
                     characters not contained in the remainder of the  scanset
                     string.  There are some conventions used in the construc-
                     tion of the scanset.  A range of characters may be repre-
                     sented by the construct first-last, thus [0123456789] may
                     be expressed [0-9].  Using this convention, first must be
                     lexically  less  than  or equal to last, or else the dash
                     will stand for itself.  The  dash  will  also  stand  for
                     itself  whenever it is the first or the last character in
                     the scanset.  To include the right square bracket  as  an
                     element of the scanset, it must appear as the first char-
                     acter (possibly preceded by a circumflex) of the scanset,
                     and in this case it will not be syntactically interpreted
                     as the closing bracket.  The corresponding argument  must
                     point  to a character array large enough to hold the data
                     field and the terminating \0, which will be  added  auto-
                     matically.   At  least  one character must match for this
                     conversion to be considered successful.

       The conversion characters d, u, o, x, and i may be preceded by l  or  h
       to indicate that a pointer to long or to short rather than to int is in
       the argument list.  Similarly, the conversion characters e,  f,  and  g
       may  be  preceded by l to indicate that a pointer to double rather than
       to float is in the argument list.  The l or h modifier is  ignored  for
       other conversion characters.

       Avoid  this  common error: because printf(3V) does not require that the
       lengths of conversion descriptors and actual parameters  match,  coders
       sometimes  are  careless with the scanf() functions.  But converting %f
       to &double or %lf to &float does not work; the results are quite incor-
       rect.

       scanf() conversion terminates at EOF, at the end of the control string,
       or when an input character conflicts with the control string.   In  the
       latter  case,  the  offending  character  is  left  unread in the input
       stream.

       scanf() returns the number of successfully matched and  assigned  input
       items;  this  number  can  be  zero  in  the event of an early conflict
       between an input character and the control string.  The constant EOF is
       returned upon end of input. Note: this is different from 0, which means
       that no conversion was done; if conversion was intended, it  was  frus-
       trated by an inappropriate character in the input.

       If  the  input  ends  before  the  first conflict or conversion, EOF is
       returned.  If the input ends after the first  conflict  or  conversion,
       the number of successfully matched items is returned.

       Conversions  can  be  applied to the nth argument in the argument list,
       rather than the next unused argument.  In  this  case,  the  conversion
       character  %  (see  below)  is  replaced by the sequence %digit$, where
       digit is a decimal integer n in the range [1,9], giving the position of
       the argument in the argument list.  This feature provides for the defi-
       nition of format strings that select arguments in an order  appropriate
       to specific languages.

       The  format  string  can contain either form of a conversion specifica-
       tion, that is % or %digit$, although the  two  forms  cannot  be  mixed
       within a single format string.

       All  forms  of  the scanf() functions allow for the detection of a lan-
       guage dependent radix character in the input string. The radix  charac-
       ter  is  defined by the program's locale (category LC_NUMERIC).  In the
       "C" locale, or in a locale where the radix character  is  not  defined,
       the radix character defaults to `.'.

SYSTEM V DESCRIPTION
       FORMFEED is allowed as a white space character in control strings.

       XPG2  requires  that  nl_scanf,  nl_fscanf  and nl_sscanf be defined as
       scanf, fscanf and sscanf, respectively for backward compatibility.

RETURN VALUES
       If any items are converted, scanf(), fscanf() and sscanf()  return  the
       number  of  items converted successfully.  This number may smaller than
       the number of items requested.  If no items are converted, these  func-
       tions  return  0.   scanf(), fscanf() and sscanf() return EOF on end of
       input.

EXAMPLES
       The call:
              int i, n; float x; char name[50];
              n = scanf("%d%f%s", &&amp;i, &&amp;x, name);

       with the input line:
              25 54.32E-1 thompson

       will assign to n the value 3, to i the value 25, to x the value  5.432,
       and name will contain thompson\0.  Or:
              int i, j; float x; char name[50];
              (void) scanf("%i%2d%f%*d %[0-9]", &&amp;j, &&amp;i, &&amp;x, name);

       with input:

              011 56789 0123 56a72

       will  assign  9  to  j,  56  to i, 789.0 to x, skip 0123, and place the
       string 56\0 in name.  The next call to getchar()  (see  getc(3V))  will
       return a.  Or:
              int i, j, s, e; char name[50];
              (void) scanf("%i %i %n%s%n", &&amp;i, &&amp;j, &&amp;s, name, &&amp;e);

       with input:
              0x11 0xy johnson

       will  assign  17  to  i,  0 to j, 6 to s, will place the string xy\0 in
       name, and will assign 8 to e.  Thus, the length of name is e - s  =  2.
       The next call to getchar() (see getc(3V)) will return a SPACE.

SEE ALSO
       getc(3V),  printf(3V),  setlocale(3V), stdio(3V), string_to_decimal(3),
       strtol(3)

WARNINGS
       Trailing white space  (including  a  NEWLINE)  is  left  unread  unless
       matched in the control string.

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



                                21 January 1990                      SCANF(3V)