printf, fprintf, sprintf - formatted output conversion
printf(format [, arg ] ... )
fprintf(stream, format [, arg ] ... )
sprintf(s, format [, arg ] ... )
char *s, format;
Printf places output on the standard output stream stdout. Fprintf places output on the
named output stream. Sprintf places `output' in the string s, followed by the character
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 suc-
cessive arg printf.
Each conversion specification is introduced by the character %. Following the %, there
- 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
- an optional digit string specifying a precision which specifies the number of dig-
its to appear after the decimal point, for e- and f-conversion, or the maximum num-
ber 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 capitalized conversion code accomplishes the same thing.)
- 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 respec-
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 specifi-
cation 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 pro-
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 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 gener-
ated by printf are printed by putc(3).
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 pi to 5 decimals:
printf("pi = %.5f", 4*atan(1.0));
putc(3), scanf(3), ecvt(3)
Very wide fields (>128 characters) fail.