scanf.3int

<B>Digital的Unix操作系统VAX 4.2源码</B>

.TH scanf 3int
.SH Name 
scanf, fscanf, sscanf \- convert formatted input
.SH Syntax 
.B #include <stdio.h>
.PP
.B int scanf(
.I format
[,
.I pointer
] ...
.B )
.br
.B char 
.IR *format ;
.PP
.B int fscanf(
.IR stream ,
.I format
[,
.I pointer
] ...
.B )
.br
.B FILE 
.IR *stream ;
.br
.B char
.IR *format ;
.PP
.B int sscanf(
.IR s ,
.I format
[, 
.I pointer
] ...
.B )
.br
.B char
.IR *s , 
.IR *format ;
.SH Description 
.NXR "scanf subroutine"
.NXR "fscanf subroutine"
.NXR "sscanf subroutine"
.NXR "scanf subroutine" "conversion specification list"
The international functions
.PN scanf ,
.PN fscanf ,
and
.PN sscanf 
are similar to the
.PN scanf
standard I/O functions. The difference is that the international
functions allow you to use the 
.I %digit$
conversion character in place of the 
.I I%
character you use in the standard I/O functions. The 
.I digit
is a decimal digit
.I n 
from 1 to 9.  The international functions apply conversions to the 
.I n
th argument in the argument list, rather than to the next unused
argument.
.PP
You can use 
.I %
conversion character in the international functions.  However, you cannot
mix the 
.I %
conversion character with the
.I %digit$
conversion character in a single call.
.PP
In all cases,
.PN scanf
uses the radix character and collating sequence that is defined by the
last successful call to
.PN setlocale
category
.PN LC_NUMERIC 
or 
.PN LC_COLLATE .
If the radix or collating sequence
is undefined, the
.PN scanf
function uses the C locale definitions.
.SS International Environment
.IP LC_COLLATE 15
Contains the user requirements for language, territory, and codeset for
the character collation format. 
.PN LC_COLLATE
affects the behavior of regular expressions and the string collation functions
in 
.PN scanf .
If 
.PN LC_COLLATE
is not defined in the current environment,
.PN LANG
provides the necessary default.
.IP LC_NUMERIC 15
If this environment is set and valid, 
.PN scanf
uses the international language database named in the definition to
determine radix character rules.
.IP LANG 15
If this environment variable is set and valid 
.PN scanf
uses the international language database named in the definition to
determine collation and character classification rules.  If
.PN LC_NUMERIC
or
.PN LC_COLLATE 
is defined,  their definitions supersede the definition of
LANG.
.SH Examples 
The following shows an example of using the
.PN scanf
function:
.EX
scanf("%2$s %1$d", integer, string)
.EE
If the input is `` january 9 '', the
.PN scanf
function assigns 9 to 
.PN integer 
and ``january'' to 
.PN string .
.SH Return Values 
The
.PN scanf
function returns the number of successfully matched
and assigned input fields.  This number can be zero if the 
.PN scanf
function encounters invalid input characters, as specified by the
conversion specification, before it can assign input characters.
.PP
If the input ends before the first conflict or conversion,
.PN scanf
returns EOF.
These functions return EOF on end of input and a short count for missing or 
invalid data items.
.SH Environment
In POSIX mode, the
.BR E ,
.BR F ,
and
.B X
formats are treated the same as the
.BR e ,
.BR f ,
and
.B x
formats, respectively; otherwise, the upper-case formats expect double, 
double, and long arguments, respectively.
.SH See Also 
intro(3int), setlocale(3), strtod(3), strtol(3), printf(3int), getc(3s), 
printf(3s), scanf(3s) 
.br
.I Guide to Developing International Software