1Printf(3)                        OCaml library                       Printf(3)
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NAME

6       Printf - Formatted output functions.
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Module

9       Module   Printf
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Documentation

12       Module Printf
13        : sig end
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16       Formatted output functions.
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24       val  fprintf  :  Pervasives.out_channel -> ('a, Pervasives.out_channel,
25       unit) Pervasives.format -> 'a
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28       fprintf outchan format arg1 ... argN formats the arguments arg1 to argN
29       according  to  the  format  string  format  , and outputs the resulting
30       string on the channel outchan .
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32       The format is a character string which contains two types  of  objects:
33       plain  characters,  which  are simply copied to the output channel, and
34       conversion specifications, each of which causes conversion and printing
35       of arguments.
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37       Conversion specifications have the following form:
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40       % [flags] [width] [.precision] type
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42       In  short, a conversion specification consists in the % character, fol‐
43       lowed by optional modifiers and a type which is  made  of  one  or  two
44       characters. The types and their meanings are:
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47       - d , i , n , l , L , or N : convert an integer argument to signed dec‐
48       imal.
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50       - u : convert an integer argument to unsigned decimal.
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52       - x : convert an integer argument to unsigned hexadecimal, using lower‐
53       case letters.
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55       - X : convert an integer argument to unsigned hexadecimal, using upper‐
56       case letters.
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58       - o : convert an integer argument to unsigned octal.
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60       - s : insert a string argument.
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62       - S : insert a string argument in Caml syntax (double quotes, escapes).
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64       - c : insert a character argument.
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66       - C : insert a  character  argument  in  Caml  syntax  (single  quotes,
67       escapes).
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69       -  f  :  convert  a floating-point argument to decimal notation, in the
70       style dddd.ddd .
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72       - F : convert a floating-point argument to  Caml  syntax  (  dddd.   or
73       dddd.ddd or d.ddd e+-dd ).
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75       -  e  or  E : convert a floating-point argument to decimal notation, in
76       the style d.ddd e+-dd (mantissa and exponent).
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78       - g or G : convert a floating-point argument to  decimal  notation,  in
79       style f or e , E (whichever is more compact).
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81       - B : convert a boolean argument to the string true or false
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84       -  b  :  convert a boolean argument (for backward compatibility; do not
85       use in new programs).
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87       - ld , li , lu , lx , lX , lo : convert an int32 argument to the format
88       specified by the second letter (decimal, hexadecimal, etc).
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90       -  nd  ,  ni  , nu , nx , nX , no : convert a nativeint argument to the
91       format specified by the second letter.
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93       - Ld , Li , Lu , Lx , LX , Lo : convert an int64 argument to the format
94       specified by the second letter.
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96       -  a  : user-defined printer. Takes two arguments and applies the first
97       one to outchan (the current output channel) and to the second argument.
98       The  first  argument must therefore have type out_channel -> 'b -> unit
99       and the second 'b .  The output produced by the function is inserted in
100       the output of fprintf at the current point.
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102       -  t  : same as %a , but takes only one argument (with type out_channel
103       -> unit ) and apply it to outchan .
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105       - { fmt %} : convert a format string argument. The argument  must  have
106       the same type as the internal format string fmt .
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108       - ( fmt %) : format string substitution. Takes a format string argument
109       and substitutes it to the internal format string fmt to print following
110       arguments. The argument must have the same type as fmt .
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112       - !  : take no argument and flush the output.
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114       - % : take no argument and output one % character.
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116       - , : the no-op delimiter for conversion specifications.
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118       The optional flags are:
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120       - - : left-justify the output (default is right justification).
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122       - 0 : for numerical conversions, pad with zeroes instead of spaces.
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124       -  +  : for numerical conversions, prefix number with a + sign if posi‐
125       tive.
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127       -space: for numerical conversions, prefix number with a space if  posi‐
128       tive.
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130       - # : request an alternate formatting style for numbers.
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132       The  optional  width  is an integer indicating the minimal width of the
133       result. For instance, %6d prints an integer, prefixing it  with  spaces
134       to fill at least 6 characters.
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136       The  optional  precision  is a dot .  followed by an integer indicating
137       how many digits follow the decimal point in the %f , %e , and  %E  con‐
138       versions. For instance, %.4f prints a float with 4 fractional digits.
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140       The  integer  in  a  width or precision can also be specified as * , in
141       which case an extra integer argument is taken  to  specify  the  corre‐
142       sponding  width  or  precision . This integer argument precedes immedi‐
143       ately the argument to print.  For instance, %.*f prints a float with as
144       many  fractional  digits  as the value of the argument given before the
145       float.
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150       val printf : ('a, Pervasives.out_channel, unit) Pervasives.format -> 'a
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152       Same as Printf.fprintf , but output on stdout .
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157       val eprintf : ('a, Pervasives.out_channel, unit)  Pervasives.format  ->
158       'a
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160       Same as Printf.fprintf , but output on stderr .
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165       val ifprintf : 'a -> ('b, 'a, unit) Pervasives.format -> 'b
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167       Same as Printf.fprintf , but does not print anything.  Useful to ignore
168       some material when conditionally printing.
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173       val sprintf : ('a, unit, string) Pervasives.format -> 'a
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175       Same as Printf.fprintf , but instead of printing on an output  channel,
176       return a string containing the result of formatting the arguments.
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181       val bprintf : Buffer.t -> ('a, Buffer.t, unit) Pervasives.format -> 'a
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183       Same  as Printf.fprintf , but instead of printing on an output channel,
184       append the formatted arguments to the given extensible buffer (see mod‐
185       ule Buffer ).
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191       === Formatted output functions with continuations. ===
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194       val kfprintf : (Pervasives.out_channel -> 'a) -> Pervasives.out_channel
195       -> ('b, Pervasives.out_channel, unit, 'a) Pervasives.format4 -> 'b
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197       Same as fprintf , but instead of returning immediately, passes the  out
198       channel to its first argument at the end of printing.
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203       val ksprintf : (string -> 'a) -> ('b, unit, string, 'a) Pervasives.for‐
204       mat4 -> 'b
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206       Same as sprintf above, but instead of returning the string,  passes  it
207       to the first argument.
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212       val kbprintf : (Buffer.t -> 'a) -> Buffer.t -> ('b, Buffer.t, unit, 'a)
213       Pervasives.format4 -> 'b
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215       Same as bprintf , but instead of returning immediately, passes the buf‐
216       fer to its first argument at the end of printing.
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221       val  kprintf : (string -> 'a) -> ('b, unit, string, 'a) Pervasives.for‐
222       mat4 -> 'b
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224       A deprecated synonym for ksprintf .
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231OCamldoc                          2017-03-22                         Printf(3)