printf.3int

<B>Digital的Unix操作系统VAX 4.2源码</B>

.TH printf 3int
.SH Name 
printf, fprintf, sprintf \- print formatted output
.SH Syntax 
.B #include <stdio.h>
.PP
.B int printf (
.I format 
[, 
.I arg
] ...
.B )
.br
char 
.IR *format ;
.PP
.B int fprintf (
.IR stream , 
.IR format 
[, 
.I arg
] ...
.B )
.br
.B FILE 
.IR *stream ;
.br
.B char 
.IR *format ;
.PP
.B int sprintf (
.IR s , 
.I format
[, 
.I arg
] ...
.B )
.br
.B char 
.IR *s , 
.IR *format ;
.SH Description 
.NXR "printf subroutine"
.NXR "fprintf subroutine"
.NXR "sprintf subroutine"
The international functions
.PN printf ,
.PN fprintf ,
and
.PN sprintf 
are similar to the 
.PN printf
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 % 
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 the
.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
You can indicate a field width or precision by an asterisk (*) instead of a
digit string in format strings containing the
.I %
conversion character. If you use an asterisk, you can supply an integer
.I arg
that specifies the field width or precision. In format strings containing the
.I %digit$
conversion character, you can indicate field width or precision 
by the sequence
.I *digit$.
You use a decimal digit from 1 to 9 to indicate which argument
contains an integer that specifies the field width or precision.
.PP
The conversion characters and their meanings are identical to
.PN printf .
.PP
You must use each 
.I digit
argument at least once.
.PP
In all cases, the radix character 
.PN printf
uses is defined by the last successful call to
.PN setlocale
category
.PN LC_NUMERIC .
If
.PN setlocale
category
.PN LC_NUMERIC
has not been called successfully or if the radix character is undefined,
the radix character defaults to a period (.).
.SS International Environment
.IP LC_NUMERIC 15
If this environment is set and valid, 
.PN printf
uses the international language database named in the definition to
determine radix character rules.
.IP LANG 15
If this environment variable is set and valid 
.PN printf
uses the international language database named in the definition to
determine collation and character classification rules.  If
.PN LC_NUMERIC 
is defined, its definition supercedes the definition of
LANG.
.SH Examples 
The following example illustrates using an argument to specify field width:
.EX 0
printf ("%1$d:%2$.*3$d:%4$.*3$d\\n",
				hour, min, precision, sec);
.EE
The format string \fI*3$\fP indicates that the third argument, which
is named precision, contains the integer field width specification.
.PP
To print the language independent date and time format use the following
.PN printf
statement:
.EX
printf (format, weekday, month, day, hour, min);
.EE
For American use,
.I format
could be a pointer to the following string:
.EX
"%1$s,  %2$s %3$d, %4$d:%5$.2d\\n"
.EE
This 
string gives the following date format:
.EX
Sunday, July 3, 10:02
.EE
For use in a German environment, 
.I format
could be a pointer to the following string:
.EX
"%1$s, %3$d. %2$s, %4$d:%5$.2d\\n"
.EE
This
string gives the following date format:
.EX
Sonntag, 3. Juli, 10:02
.EE
.SH Return Values
.NXR "printf subroutine" "System V and"
.PN printf 
and 
.PN fprintf 
return zero for success and EOF for failure.  
The
.PN sprintf 
subroutine returns its first 
argument for success and EOF for failure.
.PP
In the System V and POSIX environments, 
.PN printf ,
.PN fprintf, 
and
.PN sprintf
return the number of characters transmitted for success.  The
.PN sprintf
function ignores the null terminator (\\0) when calculating the number
of characters transmitted.  If an output error occurs, these routines
return a negative value.
.SH See Also 
intro(3int), setlocale(3), scanf(3int), printf(3s), putc(3s), scanf(3s), 
stdio(3s)
.br 
.I Guide to Developing International Software