module Printf: Printf
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 string 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 arguments.
Conversion specifications have the following form:
% [flags] [width] [.precision] type
In short, a conversion specification consists in the %
character,
followed by optional modifiers and a type which is made of one or
two characters.
The types and their meanings are:
d
, i
: convert an integer argument to signed decimal.
The flag #
adds underscores to large values for readability.u
, n
, l
, L
, or N
: convert an integer argument to
unsigned decimal. Warning: n
, l
, L
, and N
are
used for scanf
, and should not be used for printf
.
The flag #
adds underscores to large values for readability.x
: convert an integer argument to unsigned hexadecimal,
using lowercase letters.
The flag #
adds a 0x
prefix to non zero values.X
: convert an integer argument to unsigned hexadecimal,
using uppercase letters.
The flag #
adds a 0X
prefix to non zero values.o
: convert an integer argument to unsigned octal.
The flag #
adds a 0
prefix to non zero values.s
: insert a string argument.S
: convert a string argument to OCaml syntax (double quotes, escapes).c
: insert a character argument.C
: convert a character argument to OCaml syntax
(single quotes, escapes).f
: convert a floating-point argument to decimal notation,
in the style dddd.ddd
.F
: convert a floating-point argument to OCaml syntax (dddd.
or dddd.ddd
or d.ddd e+-dd
).
Converts to hexadecimal with the #
flag (see h
).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). Moreover,
any trailing zeros are removed from the fractional part of the result
and the decimal-point character is removed if there is no fractional
part remaining.h
or H
: convert a floating-point argument to hexadecimal notation,
in the style 0xh.hhhh p+-dd
(hexadecimal mantissa, exponent in
decimal and denotes a power of 2).B
: convert a boolean argument to the string true
or false
b
: convert a boolean argument (deprecated; do not use in new
programs).ld
, li
, lu
, lx
, lX
, lo
: convert an int32
argument to
the format specified by the second letter (decimal, hexadecimal, etc).nd
, ni
, nu
, nx
, nX
, no
: convert a nativeint
argument to
the format specified by the second letter.Ld
, Li
, Lu
, Lx
, LX
, Lo
: convert an int64
argument to
the format specified by the second letter.a
: user-defined printer. Take 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 inserted in the output of
fprintf
at the current point.t
: same as %a
, but take only one argument (with type
out_channel -> unit
) and apply it to outchan
.{ fmt %}
: convert a format string argument to its type digest.
The argument must have the same type as the internal format string
fmt
.( fmt %)
: format string substitution. Take a format string
argument and substitute it to the internal format string fmt
to print following arguments. The argument must have the same
type as the internal format string fmt
.!
: take no argument and flush the output.%
: take no argument and output one %
character.@
: take no argument and output one @
character.,
: take no argument and output nothing: a no-op delimiter for
conversion specifications.The optional flags
are:
-
: left-justify the output (default is right justification).0
: for numerical conversions, pad with zeroes instead of spaces.+
: for signed numerical conversions, prefix number with a +
sign if positive.#
: request an alternate formatting style for the integer types
and the floating-point type F
.The optional width
is an integer indicating the minimal
width of the result. For instance, %6d
prints an integer,
prefixing it with spaces to fill at least 6 characters.
The optional precision
is a dot .
followed by an integer
indicating how many digits follow the decimal point in the %f
,
%e
, %E
, %h
, and %H
conversions or the maximum number of
significant digits to appear for the %F
, %g
and %G
conversions.
For instance, %.4f
prints a float
with 4 fractional digits.
The integer in a width
or precision
can also be specified as
*
, in which case an extra integer argument is taken to specify
the corresponding width
or precision
. This integer argument
precedes immediately the argument to print.
For instance, %.*f
prints a float
with as many fractional
digits as the value of the argument given before the float.
val printf : ('a, out_channel, unit) format -> 'a
Same as Printf.fprintf
, but output on stdout
.
val eprintf : ('a, out_channel, unit) format -> 'a
Same as Printf.fprintf
, but output on stderr
.
val sprintf : ('a, unit, string) format -> 'a
Same as Printf.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 Printf.fprintf
, but instead of printing on an output channel,
append the formatted arguments to the given extensible buffer
(see module Buffer
).
val ifprintf : 'b -> ('a, 'b, 'c, unit) format4 -> 'a
Same as Printf.fprintf
, but does not print anything.
Useful to ignore some material when conditionally printing.
val ibprintf : Buffer.t -> ('a, Buffer.t, unit) format -> 'a
Same as Printf.bprintf
, but does not print anything.
Useful to ignore some material when conditionally printing.
Formatted output functions with continuations.
val kfprintf : (out_channel -> 'd) -> out_channel -> ('a, out_channel, unit, 'd) format4 -> 'a
Same as fprintf
, but instead of returning immediately,
passes the out channel to its first argument at the end of printing.
val ikfprintf : ('b -> 'd) -> 'b -> ('a, 'b, 'c, 'd) format4 -> 'a
Same as kfprintf
above, but does not print anything.
Useful to ignore some material when conditionally printing.
val ksprintf : (string -> 'd) -> ('a, unit, string, 'd) format4 -> 'a
Same as sprintf
above, but instead of returning the string,
passes it to the first argument.
val kbprintf : (Buffer.t -> 'd) -> Buffer.t -> ('a, Buffer.t, unit, 'd) format4 -> 'a
Same as bprintf
, but instead of returning immediately,
passes the buffer to its first argument at the end of printing.
val ikbprintf : (Buffer.t -> 'd) -> Buffer.t -> ('a, Buffer.t, unit, 'd) format4 -> 'a
Same as kbprintf
above, but does not print anything.
Useful to ignore some material when conditionally printing.
Deprecated
val kprintf : (string -> 'b) -> ('a, unit, string, 'b) format4 -> 'a
A deprecated synonym for ksprintf
.