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 depth() = -1 | integer() >= 0
23 fread_error() =
25 atom |
26 based |
27 character |
28 float |
29 format |
30 input |
31 integer |
32 string |
33 unsigned
34 fread_item() = string() | atom() | integer() | float()
36 latin1_string() = [unicode:latin1_char()]
38 format_spec() =
40 #{control_char := char(),
41 args := [any()],
42 width := none | integer(),
43 adjust := left | right,
44 precision := none | integer(),
45 pad_char := char(),
46 encoding := unicode | latin1,
47 strings := boolean()}
48 Where:
50 * control_char is the type of control sequence: $P, $w, and so
52 on.
53 * args is a list of the arguments used by the control
55 sequence, or an empty list if the control sequence does not
56 take any arguments.
57 * width is the field width.
59 * adjust is the adjustment.
61 * precision is the precision of the printed argument.
63 * pad_char is the padding character.
65 * encoding is set to true if translation modifier t is
67 present.
68 * strings is set to false if modifier l is 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
117 accordance 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 fread(Format, String) -> Result
129 Types:
131 Format = String = string()
133 Result =
134 {ok, InputList :: [fread_item()], LeftOverChars ::
135 string()} |
136 {more,
137 RestFormat :: string(),
138 Nchars :: integer() >= 0,
139 InputStack :: chars()} |
140 {error, {fread, What :: fread_error()}}
141 Tries to read String in accordance with the control sequences in
143 Format. For a detailed description of the available formatting
144 options, see io:fread/3. It is assumed that String contains
145 whole lines.
146 The function returns:
148 {ok, InputList, LeftOverChars}:
150 The string was read. InputList is the list of successfully
151 matched and read items, and LeftOverChars are the input
152 characters not used.
153 {more, RestFormat, Nchars, InputStack}:
155 The string was read, but more input is needed to complete
156 the original format string. RestFormat is the remaining for‐
157 mat string, Nchars is the number of characters scanned, and
158 InputStack is the reversed list of inputs matched up to that
159 point.
160 {error, What}:
162 The read operation failed and parameter What gives a hint
163 about the error.
164 Example:
166 3> io_lib:fread("~f~f~f", "15.6 17.3e-6 24.5").
168 {ok,[15.6,1.73e-5,24.5],[]}
169 fread(Continuation, CharSpec, Format) -> Return
171 Types:
173 Continuation = continuation() | []
175 CharSpec = string() | eof
176 Format = string()
177 Return =
178 {more, Continuation1 :: continuation()} |
179 {done, Result, LeftOverChars :: string()}
180 Result =
181 {ok, InputList :: [fread_item()]} |
182 eof |
183 {error, {fread, What :: fread_error()}}
184 This is the re-entrant formatted reader. The continuation of the
186 first call to the functions must be []. For a complete descrip‐
187 tion of how the re-entrant input scheme works, see Armstrong,
188 Virding, Williams: 'Concurrent Programming in Erlang', Chapter
189 13.
190 The function returns:
192 {done, Result, LeftOverChars}:
194 The input is complete. The result is one of the following:
195 {ok, InputList}:
197 The string was read. InputList is the list of successfully
198 matched and read items, and LeftOverChars are the remain‐
199 ing characters.
200 eof:
202 End of file was encountered. LeftOverChars are the input
203 characters not used.
204 {error, What}:
206 An error occurred and parameter What gives a hint about
207 the error.
208 {more, Continuation}:
210 More data is required to build a term. Continuation must be
211 passed to fread/3 when more data becomes available.
212 indentation(String, StartIndent) -> integer()
214 Types:
216 String = string()
218 StartIndent = integer()
219 Returns the indentation if String has been printed, starting at
221 StartIndent.
222 latin1_char_list(Term) -> boolean()
224 Types:
226 Term = term()
228 Returns true if Term is a flat list of characters in the ISO
230 Latin-1 range, otherwise false.
231 nl() -> string()
233 Returns a character list that represents a new line character.
235 print(Term) -> chars()
237 print(Term, Column, LineLength, Depth) -> chars()
239 Types:
241 Term = term()
243 Column = LineLength = integer() >= 0
244 Depth = depth()
245 Returns a list of characters that represents Term, but breaks
247 representations longer than one line into many lines and indents
248 each line sensibly. Also tries to detect and output lists of
249 printable characters as strings.
250 * Column is the starting column; defaults to 1.
252 * LineLength is the maximum line length; defaults to 80.
254 * Depth is the maximum print depth; defaults to -1, which
256 means no limitation.
257 printable_latin1_list(Term) -> boolean()
259 Types:
261 Term = term()
263 Returns true if Term is a flat list of printable ISO Latin-1
265 characters, otherwise false.
266 printable_list(Term) -> boolean()
268 Types:
270 Term = term()
272 Returns true if Term is a flat list of printable characters,
274 otherwise false.
275 What is a printable character in this case is determined by
277 startup flag +pc to the Erlang VM; see io:printable_range/0 and
278 erl(1).
279 printable_unicode_list(Term) -> boolean()
281 Types:
283 Term = term()
285 Returns true if Term is a flat list of printable Unicode charac‐
287 ters, otherwise false.
288 scan_format(Format, Data) -> FormatList
290 Types:
292 Format = io:format()
294 Data = [term()]
295 FormatList = [char() | format_spec()]
296 Returns a list corresponding to the specified format string,
298 where control sequences have been replaced with corresponding
299 tuples. This list can be passed to:
300 * build_text/1 to have the same effect as format(Format, Args)
302 * unscan_format/1 to get the corresponding pair of Format and
304 Args (with every * and corresponding argument expanded to
305 numeric values)
306 A typical use of this function is to replace unbounded-size con‐
308 trol sequences like ~w and ~p with the depth-limited variants ~W
309 and ~P before formatting to text in, for example, a logger.
310 unscan_format(FormatList) -> {Format, Data}
312 Types:
314 FormatList = [char() | format_spec()]
316 Format = io:format()
317 Data = [term()]
318 For details, see scan_format/2.
320 write(Term) -> chars()
322 write(Term, Depth) -> chars()
324 write(Term, Options) -> chars()
326 Types:
328 Term = term()
330 Options = [Option]
331 Option = {depth, Depth} | {encoding, latin1 | utf8 | unicode}
332 Depth = depth()
333 Returns a character list that represents Term. Argument Depth
335 controls the depth of the structures written. When the specified
336 depth is reached, everything below this level is replaced by
337 "...". Depth defaults to -1, which means no limitation.
338 Example:
340 1> lists:flatten(io_lib:write({1,[2],[3],[4,5],6,7,8,9})).
342 "{1,[2],[3],[4,5],6,7,8,9}"
343 2> lists:flatten(io_lib:write({1,[2],[3],[4,5],6,7,8,9}, 5)).
344 "{1,[2],[3],[...],...}"
345 write_atom(Atom) -> chars()
347 Types:
349 Atom = atom()
351 Returns the list of characters needed to print atom Atom.
353 write_atom_as_latin1(Atom) -> latin1_string()
355 Types:
357 Atom = atom()
359 Returns the list of characters needed to print atom Atom. Non-
361 Latin-1 characters are escaped.
362 write_char(Char) -> chars()
364 Types:
366 Char = char()
368 Returns the list of characters needed to print a character con‐
370 stant in the Unicode character set.
371 write_char_as_latin1(Char) -> latin1_string()
373 Types:
375 Char = char()
377 Returns the list of characters needed to print a character con‐
379 stant in the Unicode character set. Non-Latin-1 characters are
380 escaped.
381 write_latin1_char(Latin1Char) -> latin1_string()
383 Types:
385 Latin1Char = unicode:latin1_char()
387 Returns the list of characters needed to print a character con‐
389 stant in the ISO Latin-1 character set.
390 write_latin1_string(Latin1String) -> latin1_string()
392 Types:
394 Latin1String = latin1_string()
396 Returns the list of characters needed to print Latin1String as a
398 string.
399 write_string(String) -> chars()
401 Types:
403 String = string()
405 Returns the list of characters needed to print String as a
407 string.
408 write_string_as_latin1(String) -> latin1_string()
410 Types:
412 String = string()
414 Returns the list of characters needed to print String as a
416 string. Non-Latin-1 characters are escaped.
417Ericsson AB stdlib 3.4.5.1 io_lib(3)