17.20   Module Printf: formatting printing functions

val fprintf: out_channel -> ('a, out_channel, unit) format -> 'a

fprintf outchan format arg1 ... argN formats the arguments arg1 to argN according to the format string format, and outputs the resulting string on the channel outchan.

The format is a character string which contains two types of objects: plain characters, which are simply copied to the output channel, and conversion specifications, each of which causes conversion and printing of one argument.

Conversion specifications consist in the % character, followed by optional flags and field widths, followed by one conversion character. The conversion characters and their meanings are:
d or i: convert an integer argument to signed decimal
u: convert an integer argument to unsigned decimal
x: convert an integer argument to unsigned hexadecimal, using lowercase letters.
X: convert an integer argument to unsigned hexadecimal, using uppercase letters.
s: insert a string argument
c: insert a character argument
f: convert a floating-point argument to decimal notation, in the style dddd.ddd
e or E: convert a floating-point argument to decimal notation, in the style d.ddd e+-dd (mantissa and exponent)
g or G: convert a floating-point argument to decimal notation, in style f or e, E (whichever is more compact)
b: convert a boolean argument to the string true or false
a: user-defined printer. Takes two arguments and apply the first one to outchan (the current output channel) and to the second argument. The first argument must therefore have type out_channel -> 'b -> unit and the second 'b. The output produced by the function is therefore inserted in the output of fprintf at the current point.
t: same as %a, but takes only one argument (with type out_channel -> unit) and apply it to outchan.
%: take no argument and output one % character.
Refer to the C library printf function for the meaning of flags and field width specifiers.

If too few arguments are provided, printing stops just before converting the first missing argument.

val printf: ('a, out_channel, unit) format -> 'a

Same as fprintf, but output on stdout.

val eprintf: ('a, out_channel, unit) format -> 'a

Same as fprintf, but output on stderr.

val sprintf: ('a, unit, string) format -> 'a

Same as fprintf, but instead of printing on an output channel, return a string containing the result of formatting the arguments.

val bprintf: Buffer.t -> ('a, Buffer.t, unit) format -> 'a

Same as fprintf, but instead of printing on an output channel, append the formatted arguments to the given extensible buffer (see module Buffer).