PRINTF

NAME

SYNOPSIS

printf(format [, arg ] ... )
char *format;

fprintf(stream, format [, arg ] ... )
FILE *stream;
char *format;

char *sprintf(s, format [, arg ] ... )
char *s, *format;

#include <varargs.h>
vprintf(format, args)
char *format;
va_list args;

vfprintf(stream, format, args)
FILE *stream;
char *format;
va_list args;

char *vsprintf(s, format, args)
char *s, *format;
va_list args;

char *vsnprintf(s, nBytes, format, args)
char *s;
int nBytes;
char *format;
va_list args;  

DESCRIPTION

Each of these functions converts, formats, and prints the arguments that come after the format argument. The format argument controls this conversion process. It is a character string which contains two types of objects: plain characters, which are simply copied to the output stream, and conversion specifications, each of which causes conversion and printing of the next successive arg.

Each conversion specification is introduced by the character %. The remainder of the conversion specification includes in the following order

*

Zero or more of the following flags:

*

a `#' character specifying that the value should be converted to an ``alternate form''. For c, d, s, and u, conversions, this option has no effect. For o conversions, the precision of the number is increased to force the first character of the output string to a zero. For x(X) conversion, a non-zero result has the string 0x(0X) prepended to it. For e, E, f, g, and G, conversions, the result will always contain a decimal point, even if no digits follow the point (normally, a decimal point only appears in the results of those conversions if a digit follows the decimal point). For g and G conversions, trailing zeros are not removed from the result as they would otherwise be;

*

a minus sign `-' which specifies left adjustment of the converted value in the indicated field;

*

a `+' character specifying that there should always be a sign placed before the number when using signed conversions;

*

a space specifying that a blank should be left before a positive number during a signed conversion. A `+' overrides a space if both are used;

*

a zero `0' character indicating that zero-padding should be used rather than blank-padding. A `-' overrides a `0' if both are used;

*

an optional digit string specifying a field width; if the converted value has fewer characters than the field width it will be blank-padded on the left (or right, if the left-adjustment indicator has been given) to make up the field width (note that a leading zero is a flag, but an embedded zero is part of a field width);

*

an optional period, followed by an optional digit string giving a precision which specifies the number of digits to appear after the decimal point, for e- and f-conversion, or the maximum number of characters to be printed from a string; if the digit string is missing, the precision is treated as zero;

*

the character l specifying that a following d, i, o, x, or u corresponds to a long integer arg, or that a following n corresponds to a pointer to a long integer arg;

*

the character h specifying that a following d, i, o, x, or u corresponds to a short integer arg, or that a following n corresponds to a pointer to a short integer arg;

*

a character which indicates the type of conversion to be applied.

A field width or precision may be `*' instead of a digit string. In this case an integer arg supplies the field width or precision.

The conversion characters and their meanings are

dox

The integer arg is converted to signed decimal, unsigned octal, or unsigned hexadecimal notation respectively.

i

An alias for `d'.

f

The float or double arg is converted to decimal notation in the style `[-]ddd.ddd' where the number of d's after the decimal point is equal to the precision specification for the argument. If the precision is missing, 6 digits are given; if the precision is explicitly 0, no digits and no decimal point are printed.

eE

The float or double arg is converted in the style `[-]d.ddde±dd' where there is one digit before the decimal point and the number after is equal to the precision specification for the argument; when the precision is missing, 6 digits are produced. An uppercase E is used for `E' conversion.

gG

The float or double arg is printed in style f or in style e (E) whichever gives full precision in minimum space.

c

The character arg is printed.

s

Arg is taken to be a string (character pointer) and characters from the string are printed until a null character or until the number of characters indicated by the precision specification is reached; however if the precision is 0 or missing all characters up to a null are printed.

u

The unsigned integer arg is converted to decimal and printed (the result will be in the range 0 through MAXUINT, where MAXUINT equals 4294967295 on a VAX-11 and 65535 on a PDP-11).

n

Arg is taken to be a pointer to an integer (possibly short or long) through which is stored the number of characters written to the output stream (or string) so far by this call to printf (or fprintf, etc.).

p

Arg is taken to be a pointer to void; it is printed in style x.

%

Print a `%'; no argument is converted.

In no case does a non-existent or small field width cause truncation of a field; padding takes place only if the specified field width exceeds the actual width. Characters generated by printf are printed as by putc(3S).

RETURN VALUE

EXAMPLES

printf("%s, %s %d, %02d:%02d", weekday, month, day, hour, min);

To print pi to 5 decimals:

printf("pi = %.5f", 4*atan(1.0));

SEE ALSO

BUGS

For ANSI compatibility, the sprintf family should return the number of characters printed, rather than the buffer string.

Index

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

EXAMPLES

SEE ALSO

BUGS