1io_lib(3) Erlang Module Definition io_lib(3)
2
6 io_lib - I/O library functions.
7
9 This module contains functions for converting to and from strings
10 (lists of characters). They are used for implementing the functions in
11 the io module. There is no guarantee that the character lists returned
12 from some of the functions are flat, they can be deep lists. Function
13 lists:flatten/1 can be used for flattening deep lists.
14
16 chars() = [char() | chars()]
17 continuation()
19 A continuation as returned by fread/3.
21 chars_limit() = integer()
23 depth() = -1 | integer() >= 0
25 fread_error() =
27 atom | based | character | float | format | input | integer |
28 string | unsigned
29 fread_item() = string() | atom() | integer() | float()
31 latin1_string() = [unicode:latin1_char()]
33 format_spec() =
35 #{control_char := char(),
36 args := [any()],
37 width := none | integer(),
38 adjust := left | right,
39 precision := none | integer(),
40 pad_char := char(),
41 encoding := unicode | latin1,
42 strings := boolean(),
43 maps_order => maps:iterator_order()}
44 Where:
46 * control_char is the type of control sequence: $P, $w, and so
48 on.
49 * args is a list of the arguments used by the control se‐
51 quence, or an empty list if the control sequence does not
52 take any arguments.
53 * width is the field width.
55 * adjust is the adjustment.
57 * precision is the precision of the printed argument.
59 * pad_char is the padding character.
61 * encoding is set to true if translation modifier t is
63 present.
64 * strings is set to false if modifier l is present.
66 * maps_order is set to undefined by default, ordered if modi‐
68 fier k is present, or reversed or CmpFun if modifier K is
69 present.
70
72 build_text(FormatList) -> chars()
73 Types:
75 FormatList = [char() | format_spec()]
77 For details, see scan_format/2.
79 char_list(Term) -> boolean()
81 Types:
83 Term = term()
85 Returns true if Term is a flat list of characters in the Unicode
87 range, otherwise false.
88 deep_char_list(Term) -> boolean()
90 Types:
92 Term = term()
94 Returns true if Term is a, possibly deep, list of characters in
96 the Unicode range, otherwise false.
97 deep_latin1_char_list(Term) -> boolean()
99 Types:
101 Term = term()
103 Returns true if Term is a, possibly deep, list of characters in
105 the ISO Latin-1 range, otherwise false.
106 format(Format, Data) -> chars()
108 fwrite(Format, Data) -> chars()
110 Types:
112 Format = io:format()
114 Data = [term()]
115 Returns a character list that represents Data formatted in ac‐
117 cordance with Format. For a detailed description of the avail‐
118 able formatting options, see io:fwrite/1,2,3. If the format
119 string or argument list contains an error, a fault is generated.
120 If and only if the Unicode translation modifier is used in the
122 format string (that is, ~ts or ~tc), the resulting list can con‐
123 tain characters beyond the ISO Latin-1 character range (that is,
124 numbers > 255). If so, the result is still an ordinary Erlang
125 string(), and can well be used in any context where Unicode data
126 is allowed.
127 format(Format, Data, Options) -> chars()
129 fwrite(Format, Data, Options) -> chars()
131 Types:
133 Format = io:format()
135 Data = [term()]
136 Options = [Option]
137 Option = {chars_limit, CharsLimit}
138 CharsLimit = chars_limit()
139 Returns a character list that represents Data formatted in ac‐
141 cordance with Format in the same way as fwrite/2 and format/2,
142 but takes an extra argument, a list of options.
143 Valid option:
145 {chars_limit, CharsLimit}:
147 A soft limit on the number of characters returned. When the
148 number of characters is reached, remaining structures are
149 replaced by "...". CharsLimit defaults to -1, which means no
150 limit on the number of characters returned.
151 fread(Format, String) -> Result
153 Types:
155 Format = String = string()
157 Result =
158 {ok, InputList :: [fread_item()], LeftOverChars ::
159 string()} |
160 {more,
161 RestFormat :: string(),
162 Nchars :: integer() >= 0,
163 InputStack :: chars()} |
164 {error, {fread, What :: fread_error()}}
165 Tries to read String in accordance with the control sequences in
167 Format. For a detailed description of the available formatting
168 options, see io:fread/3. It is assumed that String contains
169 whole lines.
170 The function returns:
172 {ok, InputList, LeftOverChars}:
174 The string was read. InputList is the list of successfully
175 matched and read items, and LeftOverChars are the input
176 characters not used.
177 {more, RestFormat, Nchars, InputStack}:
179 The string was read, but more input is needed to complete
180 the original format string. RestFormat is the remaining for‐
181 mat string, Nchars is the number of characters scanned, and
182 InputStack is the reversed list of inputs matched up to that
183 point.
184 {error, What}:
186 The read operation failed and parameter What gives a hint
187 about the error.
188 Example:
190 3> io_lib:fread("~f~f~f", "15.6 17.3e-6 24.5").
192 {ok,[15.6,1.73e-5,24.5],[]}
193 fread(Continuation, CharSpec, Format) -> Return
195 Types:
197 Continuation = continuation() | []
199 CharSpec = string() | eof
200 Format = string()
201 Return =
202 {more, Continuation1 :: continuation()} |
203 {done, Result, LeftOverChars :: string()}
204 Result =
205 {ok, InputList :: [fread_item()]} |
206 eof |
207 {error, {fread, What :: fread_error()}}
208 This is the re-entrant formatted reader. The continuation of the
210 first call to the functions must be []. For a complete descrip‐
211 tion of how the re-entrant input scheme works, see Armstrong,
212 Virding, Williams: 'Concurrent Programming in Erlang', Chapter
213 13.
214 The function returns:
216 {done, Result, LeftOverChars}:
218 The input is complete. The result is one of the following:
219 {ok, InputList}:
221 The string was read. InputList is the list of successfully
222 matched and read items, and LeftOverChars are the remain‐
223 ing characters.
224 eof:
226 End of file was encountered. LeftOverChars are the input
227 characters not used.
228 {error, What}:
230 An error occurred and parameter What gives a hint about
231 the error.
232 {more, Continuation}:
234 More data is required to build a term. Continuation must be
235 passed to fread/3 when more data becomes available.
236 indentation(String, StartIndent) -> integer()
238 Types:
240 String = string()
242 StartIndent = integer()
243 Returns the indentation if String has been printed, starting at
245 StartIndent.
246 latin1_char_list(Term) -> boolean()
248 Types:
250 Term = term()
252 Returns true if Term is a flat list of characters in the ISO
254 Latin-1 range, otherwise false.
255 nl() -> string()
257 Returns a character list that represents a new line character.
259 print(Term) -> chars()
261 print(Term, Column, LineLength, Depth) -> chars()
263 Types:
265 Term = term()
267 Column = LineLength = integer() >= 0
268 Depth = depth()
269 Returns a list of characters that represents Term, but breaks
271 representations longer than one line into many lines and indents
272 each line sensibly. Also tries to detect and output lists of
273 printable characters as strings.
274 * Column is the starting column; defaults to 1.
276 * LineLength is the maximum line length; defaults to 80.
278 * Depth is the maximum print depth; defaults to -1, which
280 means no limitation.
281 printable_latin1_list(Term) -> boolean()
283 Types:
285 Term = term()
287 Returns true if Term is a flat list of printable ISO Latin-1
289 characters, otherwise false.
290 printable_list(Term) -> boolean()
292 Types:
294 Term = term()
296 Returns true if Term is a flat list of printable characters,
298 otherwise false.
299 What is a printable character in this case is determined by
301 startup flag +pc to the Erlang VM; see io:printable_range/0 and
302 erl(1).
303 printable_unicode_list(Term) -> boolean()
305 Types:
307 Term = term()
309 Returns true if Term is a flat list of printable Unicode charac‐
311 ters, otherwise false.
312 scan_format(Format, Data) -> FormatList
314 Types:
316 Format = io:format()
318 Data = [term()]
319 FormatList = [char() | format_spec()]
320 Returns a list corresponding to the specified format string,
322 where control sequences have been replaced with corresponding
323 tuples. This list can be passed to:
324 * build_text/1 to have the same effect as format(Format, Args)
326 * unscan_format/1 to get the corresponding pair of Format and
328 Args (with every * and corresponding argument expanded to
329 numeric values)
330 A typical use of this function is to replace unbounded-size con‐
332 trol sequences like ~w and ~p with the depth-limited variants ~W
333 and ~P before formatting to text in, for example, a logger.
334 unscan_format(FormatList) -> {Format, Data}
336 Types:
338 FormatList = [char() | format_spec()]
340 Format = io:format()
341 Data = [term()]
342 For details, see scan_format/2.
344 write(Term) -> chars()
346 write(Term, Depth) -> chars()
348 write(Term, Options) -> chars()
350 Types:
352 Term = term()
354 Options = [Option]
355 Option =
356 {chars_limit, CharsLimit} |
357 {depth, Depth} |
358 {encoding, latin1 | utf8 | unicode}
359 CharsLimit = chars_limit()
360 Depth = depth()
361 Returns a character list that represents Term. Option Depth con‐
363 trols the depth of the structures written. When the specified
364 depth is reached, everything below this level is replaced by
365 "...". Depth defaults to -1, which means no limitation. Option
366 CharsLimit puts a soft limit on the number of characters re‐
367 turned. When the number of characters is reached, remaining
368 structures are replaced by "...". CharsLimit defaults to -1,
369 which means no limit on the number of characters returned.
370 Example:
372 1> lists:flatten(io_lib:write({1,[2],[3],[4,5],6,7,8,9})).
374 "{1,[2],[3],[4,5],6,7,8,9}"
375 2> lists:flatten(io_lib:write({1,[2],[3],[4,5],6,7,8,9}, 5)).
376 "{1,[2],[3],[...],...}"
377 3> lists:flatten(io_lib:write({[1,2,3],[4,5],6,7,8,9}, [{chars_limit,20}])).
378 "{[1,2|...],[4|...],...}"
379 write_atom(Atom) -> chars()
381 Types:
383 Atom = atom()
385 Returns the list of characters needed to print atom Atom.
387 write_atom_as_latin1(Atom) -> latin1_string()
389 Types:
391 Atom = atom()
393 Returns the list of characters needed to print atom Atom. Non-
395 Latin-1 characters are escaped.
396 write_char(Char) -> chars()
398 Types:
400 Char = char()
402 Returns the list of characters needed to print a character con‐
404 stant in the Unicode character set.
405 write_char_as_latin1(Char) -> latin1_string()
407 Types:
409 Char = char()
411 Returns the list of characters needed to print a character con‐
413 stant in the Unicode character set. Non-Latin-1 characters are
414 escaped.
415 write_latin1_char(Latin1Char) -> latin1_string()
417 Types:
419 Latin1Char = unicode:latin1_char()
421 Returns the list of characters needed to print a character con‐
423 stant in the ISO Latin-1 character set.
424 write_latin1_string(Latin1String) -> latin1_string()
426 Types:
428 Latin1String = latin1_string()
430 Returns the list of characters needed to print Latin1String as a
432 string.
433 write_string(String) -> chars()
435 Types:
437 String = string()
439 Returns the list of characters needed to print String as a
441 string.
442 write_string_as_latin1(String) -> latin1_string()
444 Types:
446 String = string()
448 Returns the list of characters needed to print String as a
450 string. Non-Latin-1 characters are escaped.
451Ericsson AB stdlib 5.1.1 io_lib(3)