Printf(3o) OCaml library Printf(3o)
NAME
Printf - Formatted output functions.
Module
Module Printf
Documentation
Module Printf
: sig end
Formatted output 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 string is a character string which contains two types of ob-
jects: 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, fol-
lowed 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 deci-
mal. 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 lower-
case letters. The flag # adds a 0x prefix to non zero values.
- X : convert an integer argument to unsigned hexadecimal, using upper-
case 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, es-
capes).
- c : insert a character argument.
- C : convert a character argument to OCaml syntax (single quotes, es-
capes).
- 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 deci-
mal-point character is removed if there is no fractional part remain-
ing.
- 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 pro-
grams).
- 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 con-
version 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.
-space: for signed numerical conversions, prefix number with a space 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 corre-
sponding width or precision . This integer argument precedes immedi-
ately 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 mod-
ule 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.
Since 3.10.0
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.
Since 4.11.0
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.
Since 3.09.0
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.
Since 4.01.0
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.
Since 3.09.0
val kbprintf : (Buffer.t -> 'd) -> Buffer.t -> ('a, Buffer.t, unit, 'd)
format4 -> 'a
Same as bprintf , but instead of returning immediately, passes the buf-
fer to its first argument at the end of printing.
Since 3.10.0
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.
Since 4.11.0
Deprecated
val kprintf : (string -> 'b) -> ('a, unit, string, 'b) format4 -> 'a
A deprecated synonym for ksprintf .
OCamldoc 2023-02-12 Printf(3o)
Generated by dwww version 1.15 on Thu Jun 20 17:34:55 CEST 2024.