printf(3s)
NAME
printf, fprintf, sprintf − formatted output conversion
SYNTAX
#include <stdio.h>
int printf(format [, arg] ...)
char *format;
int fprintf(stream, format, [, arg] ...)
FILE *stream;
char *format;
int sprintf(s, format [, arg] ...)
char *s, *format;
DESCRIPTION
The printf subroutine places output on the standard output stream stdout. The fprintf subroutine places output on the named output stream. The sprintf subroutine places output in the string s, followed by the character \0.
Each of these functions converts, formats, and prints its arguments after the first under control of the first argument. The first argument 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 printf.
Each conversion specification is introduced by the character %. Following the %, there may be:
• An optional minus sign − which specifies left adjustment of the converted value in the indicated field.
• 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; if the field width begins with a zero, zero-padding will be done instead of blank-padding.
• An optional period . which serves to separate the field width from the next digit string.
• An optional digit string specifying 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;
• The character l specifying that a following d, o, x, or u corresponds to a long 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 decimal, octal, or hexadecimal notation, respectively.
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.
e 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.
g The float or double arg is printed in style d, in style f, or in style e, whichever gives full precision in minimum space.
c The character arg is printed. Null characters are ignored.
s The 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 to 65535).
% 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 by putc(3s).
RETURN VALUES
For programs compiled under the default, ULTRIX-11 environment:
•printf and fprintf return 0 on success.
•sprintf returns a pointer to the buffer containing the argument string on success.
For programs compiled under the SYSTEM V environment:
•printf, fprintf, and sprintf return a character count (number of characters placed into the buffer).
EXAMPLES
To print a date and time in the form ’Sunday, July 3, 10:02’, where weekday and month are pointers to null-terminated strings:
printf("%s, %s %d, %02d:%02d", weekday, month, day, hour, min);
To print π to 5 decimals:
printf("pi = %.5f", 4*atan(1.0));
RESTRICTIONS
Fields greater than 128 characters fail.
The format specifications %U and %X are not recognized in this current version of printf. These format specifications, however, are provided in the old, Version 7 printf routine, which is found in /usr/orphan/lib/libv7.a (loaded as optional software).