1Printf(3)                        OCaml library                       Printf(3)
2
3
4

NAME

6       Printf - Formatted output functions.
7

Module

9       Module   Printf
10

Documentation

12       Module Printf
13        : sig end
14
15
16       Formatted output functions.
17
18
19
20
21
22
23       val fprintf : out_channel -> ('a, out_channel, unit) format -> 'a
24
25
26       fprintf outchan format arg1 ... argN formats the arguments arg1 to argN
27       according to the format string  format  ,  and  outputs  the  resulting
28       string on the channel outchan .
29
30       The  format  string  is  a character string which contains two types of
31       objects: plain characters, which are simply copied to the output  chan‐
32       nel, and conversion specifications, each of which causes conversion and
33       printing of arguments.
34
35       Conversion specifications have the following form:
36
37
38       % [flags] [width] [.precision] type
39
40       In short, a conversion specification consists in the % character,  fol‐
41       lowed  by  optional  modifiers  and  a type which is made of one or two
42       characters.
43
44       The types and their meanings are:
45
46
47       - d , i : convert an integer argument to signed decimal.
48
49       - u , n , l , L , or N : convert an integer argument to unsigned  deci‐
50       mal.  Warning: n , l , L , and N are used for scanf , and should not be
51       used for printf .
52
53       - x : convert an integer argument to unsigned hexadecimal, using lower‐
54       case letters.
55
56       - X : convert an integer argument to unsigned hexadecimal, using upper‐
57       case letters.
58
59       - o : convert an integer argument to unsigned octal.
60
61       - s : insert a string argument.
62
63       - S : convert  a  string  argument  to  OCaml  syntax  (double  quotes,
64       escapes).
65
66       - c : insert a character argument.
67
68       -  C  :  convert  a  character argument to OCaml syntax (single quotes,
69       escapes).
70
71       - f : convert a floating-point argument to  decimal  notation,  in  the
72       style dddd.ddd .
73
74       -  F  :  convert  a floating-point argument to OCaml syntax ( dddd.  or
75       dddd.ddd or d.ddd e+-dd ).
76
77       - e or E : convert a floating-point argument to  decimal  notation,  in
78       the style d.ddd e+-dd (mantissa and exponent).
79
80       -  g  or  G : convert a floating-point argument to decimal notation, in
81       style f or e , E (whichever is more compact).  Moreover,  any  trailing
82       zeros  are removed from the fractional part of the result and the deci‐
83       mal-point character is removed if there is no fractional  part  remain‐
84       ing.
85
86       -  h  or H : convert a floating-point argument to hexadecimal notation,
87       in the style 0xh.hhhh e+-dd (hexadecimal mantissa, exponent in  decimal
88       and denotes a power of 2).
89
90       - B : convert a boolean argument to the string true or false
91
92
93       -  b  :  convert a boolean argument (deprecated; do not use in new pro‐
94       grams).
95
96       - ld , li , lu , lx , lX , lo : convert an int32 argument to the format
97       specified by the second letter (decimal, hexadecimal, etc).
98
99       -  nd  ,  ni  , nu , nx , nX , no : convert a nativeint argument to the
100       format specified by the second letter.
101
102       - Ld , Li , Lu , Lx , LX , Lo : convert an int64 argument to the format
103       specified by the second letter.
104
105       -  a : user-defined printer. Take two arguments and apply the first one
106       to outchan (the current output channel) and to the second argument. The
107       first  argument  must therefore have type out_channel -> 'b -> unit and
108       the second 'b .  The output produced by the function is inserted in the
109       output of fprintf at the current point.
110
111       - t : same as %a , but take only one argument (with type out_channel ->
112       unit ) and apply it to outchan .
113
114       - { fmt %} : convert a format string argument to its type digest.   The
115       argument must have the same type as the internal format string fmt .
116
117       -  ( fmt %) : format string substitution. Take a format string argument
118       and substitute it to the internal format string fmt to print  following
119       arguments.  The argument must have the same type as the internal format
120       string fmt .
121
122       - !  : take no argument and flush the output.
123
124       - % : take no argument and output one % character.
125
126       - @ : take no argument and output one @ character.
127
128       - , : take no argument and output nothing: a no-op delimiter  for  con‐
129       version specifications.
130
131       The optional flags are:
132
133       - - : left-justify the output (default is right justification).
134
135       - 0 : for numerical conversions, pad with zeroes instead of spaces.
136
137       -  + : for signed numerical conversions, prefix number with a + sign if
138       positive.
139
140       -space: for signed numerical conversions, prefix number with a space if
141       positive.
142
143       - # : request an alternate formatting style for the integer types ( x ,
144       X , o , lx , lX , lo , Lx , LX , Lo , d , i , u , ld , li , lu ,  Ld  ,
145       Li , Lu , nd , ni , nu ).
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.
150
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.
154
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.
161
162
163
164       val printf : ('a, out_channel, unit) format -> 'a
165
166       Same as Printf.fprintf , but output on stdout .
167
168
169
170       val eprintf : ('a, out_channel, unit) format -> 'a
171
172       Same as Printf.fprintf , but output on stderr .
173
174
175
176       val sprintf : ('a, unit, string) format -> 'a
177
178       Same as Printf.fprintf , but instead of printing on an output  channel,
179       return a string containing the result of formatting the arguments.
180
181
182
183       val bprintf : Buffer.t -> ('a, Buffer.t, unit) format -> 'a
184
185       Same  as Printf.fprintf , but instead of printing on an output channel,
186       append the formatted arguments to the given extensible buffer (see mod‐
187       ule Buffer ).
188
189
190
191       val ifprintf : 'b -> ('a, 'b, 'c, unit) format4 -> 'a
192
193       Same as Printf.fprintf , but does not print anything.  Useful to ignore
194       some material when conditionally printing.
195
196
197       Since 3.10.0
198
199
200
201
202       Formatted output functions with continuations.
203
204       val kfprintf : (out_channel -> 'd) -> out_channel -> ('a,  out_channel,
205       unit, 'd) format4 -> 'a
206
207       Same  as fprintf , but instead of returning immediately, passes the out
208       channel to its first argument at the end of printing.
209
210
211       Since 3.09.0
212
213
214
215       val ikfprintf : ('b -> 'd) -> 'b -> ('a, 'b, 'c, 'd) format4 -> 'a
216
217       Same as kfprintf above, but does not print anything.  Useful to  ignore
218       some material when conditionally printing.
219
220
221       Since 4.01.0
222
223
224
225       val ksprintf : (string -> 'd) -> ('a, unit, string, 'd) format4 -> 'a
226
227       Same  as  sprintf above, but instead of returning the string, passes it
228       to the first argument.
229
230
231       Since 3.09.0
232
233
234
235       val kbprintf : (Buffer.t -> 'd) -> Buffer.t -> ('a, Buffer.t, unit, 'd)
236       format4 -> 'a
237
238       Same as bprintf , but instead of returning immediately, passes the buf‐
239       fer to its first argument at the end of printing.
240
241
242       Since 3.10.0
243
244
245
246
247       Deprecated
248
249       val kprintf : (string -> 'b) -> ('a, unit, string, 'b) format4 -> 'a
250
251       A deprecated synonym for ksprintf .
252
253
254
255
256
257OCamldoc                          2019-07-30                         Printf(3)