PRINTF(3S)                           BSD                            PRINTF(3S)



NAME
     printf, fprintf, sprintf - formatted output conversion

SYNOPSIS
     #include <stdio.h>

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

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

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

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

DESCRIPTION
     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 "\0".  All of these routines work by
     calling the internal routine _doprnt, using the variable-length argument
     facilities of varargs(3).

     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 that 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 percent character (%).
     The remainder of the conversion specification includes in the following
     order:

     ⊕  Zero or more of following flags:

        #       (Sharp sign.)  Specifies 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 0.  For x(X) conversion, a nonzero 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
                0s are not removed from the result as they would otherwise be.

        -       (Minus sign.)  Specifies left adjustment of the converted
                value in the indicated field.

        +       (Plus sign.)  Specifies that there should always be a sign
                placed before the number when using signed conversions.

        space   (A space character.)  Specifies that a blank should be left

                before a positive number during a signed conversion.  A "+"
                overrides a space 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; if the field width begins with
        a 0, 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 (el), 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 can be an asterisk (*) 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.

     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.

     %     Print a percent sign (%); 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).

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, do this:

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

     To print pi to 5 decimals, do this:

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

SEE ALSO
     putc(3S), scanf(3S), ecvt(3)

BUGS
     Very wide fields (>128 characters) fail.