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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23       val  fprintf  :  Pervasives.out_channel -> ('a, Pervasives.out_channel,
24       unit) Pervasives.format -> 'a
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26
27       fprintf outchan format arg1 ... argN formats the arguments arg1 to argN
28       according  to  the  format  string  format  , and outputs the resulting
29       string on the channel outchan .
30
31       The format string is a character string which  contains  two  types  of
32       objects:  plain characters, which are simply copied to the output chan‐
33       nel, and conversion specifications, each of which causes conversion and
34       printing of arguments.
35
36       Conversion specifications have the following form:
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39       % [flags] [width] [.precision] type
40
41       In  short, a conversion specification consists in the % character, fol‐
42       lowed by optional modifiers and a type which is  made  of  one  or  two
43       characters.
44
45       The types and their meanings are:
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48       - d , i : convert an integer argument to signed decimal.
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50       -  u , n , l , L , or N : convert an integer argument to unsigned deci‐
51       mal.  Warning: n , l , L , and N are used for scanf , and should not be
52       used for printf .
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54       - x : convert an integer argument to unsigned hexadecimal, using lower‐
55       case letters.
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57       - X : convert an integer argument to unsigned hexadecimal, using upper‐
58       case letters.
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60       - o : convert an integer argument to unsigned octal.
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62       - s : insert a string argument.
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64       -  S  :  convert  a  string  argument  to  OCaml syntax (double quotes,
65       escapes).
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67       - c : insert a character argument.
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69       - C : convert a character argument  to  OCaml  syntax  (single  quotes,
70       escapes).
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72       -  f  :  convert  a floating-point argument to decimal notation, in the
73       style dddd.ddd .
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75       - F : convert a floating-point argument to OCaml  syntax  (  dddd.   or
76       dddd.ddd or d.ddd e+-dd ).
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78       -  e  or  E : convert a floating-point argument to decimal notation, in
79       the style d.ddd e+-dd (mantissa and exponent).
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81       - g or G : convert a floating-point argument to  decimal  notation,  in
82       style  f  or  e , E (whichever is more compact). Moreover, any trailing
83       zeros are removed from the fractional part of the result and the  deci‐
84       mal-point  character  is removed if there is no fractional part remain‐
85       ing.
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87       - h or H : convert a floating-point argument to  hexadecimal  notation,
88       in  the style 0xh.hhhh e+-dd (hexadecimal mantissa, exponent in decimal
89       and denotes a power of 2).
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91       - B : convert a boolean argument to the string true or false
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93
94       - b : convert a boolean argument (deprecated; do not use  in  new  pro‐
95       grams).
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97       - ld , li , lu , lx , lX , lo : convert an int32 argument to the format
98       specified by the second letter (decimal, hexadecimal, etc).
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100       - nd , ni , nu , nx , nX , no : convert a  nativeint  argument  to  the
101       format specified by the second letter.
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103       - Ld , Li , Lu , Lx , LX , Lo : convert an int64 argument to the format
104       specified by the second letter.
105
106       - a : user-defined printer. Take two arguments and apply the first  one
107       to outchan (the current output channel) and to the second argument. The
108       first argument must therefore have type out_channel -> 'b ->  unit  and
109       the second 'b .  The output produced by the function is inserted in the
110       output of fprintf at the current point.
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112       - t : same as %a , but take only one argument (with type out_channel ->
113       unit ) and apply it to outchan .
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115       -  { fmt %} : convert a format string argument to its type digest.  The
116       argument must have the same type as the internal format string fmt .
117
118       - ( fmt %) : format string substitution. Take a format string  argument
119       and  substitute it to the internal format string fmt to print following
120       arguments. The argument must have the same type as the internal  format
121       string fmt .
122
123       - !  : take no argument and flush the output.
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125       - % : take no argument and output one % character.
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127       - @ : take no argument and output one @ character.
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129       -  ,  : take no argument and output nothing: a no-op delimiter for con‐
130       version specifications.
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132       The optional flags are:
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134       - - : left-justify the output (default is right justification).
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136       - 0 : for numerical conversions, pad with zeroes instead of spaces.
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138       - + : for signed numerical conversions, prefix number with a + sign  if
139       positive.
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141       -space: for signed numerical conversions, prefix number with a space if
142       positive.
143
144       - # : request an alternate formatting style  for  the  hexadecimal  and
145       octal integer types ( x , X , o , lx , lX , lo , Lx , LX , Lo ).
146
147       The  optional  width  is an integer indicating the minimal width of the
148       result. For instance, %6d prints an integer, prefixing it  with  spaces
149       to fill at least 6 characters.
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151       The  optional  precision  is a dot .  followed by an integer indicating
152       how many digits follow the decimal point in the %f , %e , and  %E  con‐
153       versions. For instance, %.4f prints a float with 4 fractional digits.
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155       The  integer  in  a  width or precision can also be specified as * , in
156       which case an extra integer argument is taken  to  specify  the  corre‐
157       sponding  width  or  precision . This integer argument precedes immedi‐
158       ately the argument to print.  For instance, %.*f prints a float with as
159       many  fractional  digits  as the value of the argument given before the
160       float.
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164       val printf : ('a, Pervasives.out_channel, unit) Pervasives.format -> 'a
165
166       Same as Printf.fprintf , but output on stdout .
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170       val eprintf : ('a, Pervasives.out_channel, unit)  Pervasives.format  ->
171       'a
172
173       Same as Printf.fprintf , but output on stderr .
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177       val sprintf : ('a, unit, string) Pervasives.format -> 'a
178
179       Same  as Printf.fprintf , but instead of printing on an output channel,
180       return a string containing the result of formatting the arguments.
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184       val bprintf : Buffer.t -> ('a, Buffer.t, unit) Pervasives.format -> 'a
185
186       Same as Printf.fprintf , but instead of printing on an output  channel,
187       append the formatted arguments to the given extensible buffer (see mod‐
188       ule Buffer ).
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192       val ifprintf : 'b -> ('a, 'b, 'c, unit) Pervasives.format4 -> 'a
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194       Same as Printf.fprintf , but does not print anything.  Useful to ignore
195       some material when conditionally printing.
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197
198       Since 3.10.0
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202
203       === Formatted output functions with continuations. ===
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206       val kfprintf : (Pervasives.out_channel -> 'd) -> Pervasives.out_channel
207       -> ('a, Pervasives.out_channel, unit, 'd) Pervasives.format4 -> 'a
208
209       Same as fprintf , but instead of returning immediately, passes the  out
210       channel to its first argument at the end of printing.
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212
213       Since 3.09.0
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217       val ikfprintf : ('b -> 'd) -> 'b -> ('a, 'b, 'c, 'd) Pervasives.format4
218       -> 'a
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220       Same as kfprintf above, but does not print anything.  Useful to  ignore
221       some material when conditionally printing.
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223
224       Since 4.01.0
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228       val ksprintf : (string -> 'd) -> ('a, unit, string, 'd) Pervasives.for‐
229       mat4 -> 'a
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231       Same as sprintf above, but instead of returning the string,  passes  it
232       to the first argument.
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235       Since 3.09.0
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239       val kbprintf : (Buffer.t -> 'd) -> Buffer.t -> ('a, Buffer.t, unit, 'd)
240       Pervasives.format4 -> 'a
241
242       Same as bprintf , but instead of returning immediately, passes the buf‐
243       fer to its first argument at the end of printing.
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245
246       Since 3.10.0
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251       === Deprecated ===
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254       val  kprintf : (string -> 'b) -> ('a, unit, string, 'b) Pervasives.for‐
255       mat4 -> 'a
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257       A deprecated synonym for ksprintf .
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263OCamldoc                          2018-07-14                         Printf(3)