<?xml version="1.0" encoding="latin1" ?> <!DOCTYPE erlref SYSTEM "erlref.dtd"> <erlref> <header> <copyright> <year>1996</year><year>2009</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> The contents of this file are subject to the Erlang Public License, Version 1.1, (the "License"); you may not use this file except in compliance with the License. You should have received a copy of the Erlang Public License along with this software. If not, it can be retrieved online at http://www.erlang.org/. Software distributed under the License is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for the specific language governing rights and limitations under the License. </legalnotice> <title>io_lib</title> <prepared></prepared> <docno></docno> <date></date> <rev></rev> </header> <module>io_lib</module> <modulesummary>IO Library Functions</modulesummary> <description> <p>This module contains functions for converting to and from strings (lists of characters). They are used for implementing the functions in the <c>io</c> module. There is no guarantee that the character lists returned from some of the functions are flat, they can be deep lists. <c>lists:flatten/1</c> can be used for flattening deep lists.</p> </description> <section> <title>DATA TYPES</title> <code type="none"> chars() = [char() | chars()]</code> </section> <funcs> <func> <name>nl() -> chars()</name> <fsummary>Write a newline</fsummary> <desc> <p>Returns a character list which represents a new line character.</p> </desc> </func> <func> <name>write(Term) -></name> <name>write(Term, Depth) -> chars()</name> <fsummary>Write a term</fsummary> <type> <v>Term = term()</v> <v>Depth = int()</v> </type> <desc> <p>Returns a character list which represents <c>Term</c>. The <c>Depth</c> (-1) argument controls the depth of the structures written. When the specified depth is reached, everything below this level is replaced by "...". For example:</p> <pre> 1> <input>lists:flatten(io_lib:write({1,[2],[3],[4,5],6,7,8,9})).</input> "{1,[2],[3],[4,5],6,7,8,9}" 2> <input>lists:flatten(io_lib:write({1,[2],[3],[4,5],6,7,8,9}, 5)).</input> "{1,[2],[3],[...],...}"</pre> </desc> </func> <func> <name>print(Term) -></name> <name>print(Term, Column, LineLength, Depth) -> chars()</name> <fsummary>Pretty print a term</fsummary> <type> <v>Term = term()</v> <v>Column = LineLenght = Depth = int()</v> </type> <desc> <p>Also returns a list of characters which represents <c>Term</c>, but breaks representations which are longer than one line into many lines and indents each line sensibly. It also tries to detect and output lists of printable characters as strings. <c>Column</c> is the starting column (1), <c>LineLength</c> the maximum line length (80), and <c>Depth</c> (-1) the maximum print depth.</p> </desc> </func> <func> <name>fwrite(Format, Data) -></name> <name>format(Format, Data) -> chars() | UnicodeList</name> <fsummary>Write formatted output</fsummary> <type> <v>Format = atom() | string() | binary()</v> <v>Data = [term()]</v> <v>UnicodeList = [Unicode]</v> <v>Unicode = int() representing valid unicode codepoint</v> </type> <desc> <p>Returns a character list which represents <c>Data</c> formatted in accordance with <c>Format</c>. See <seealso marker="io#fwrite/1">io:fwrite/1,2,3</seealso> for a detailed description of the available formatting options. A fault is generated if there is an error in the format string or argument list.</p> <p>If (and only if) the Unicode translation modifier is used in the format string (i.e. ~ts or ~tc), the resulting list may contain characters beyond the ISO-latin-1 character range (in other words, numbers larger than 255). If so, the result is not an ordinary Erlang string(), but can well be used in any context where Unicode data is allowed.</p> </desc> </func> <func> <name>fread(Format, String) -> Result</name> <fsummary>Read formatted input</fsummary> <type> <v>Format = String = string()</v> <v>Result = {ok, InputList, LeftOverChars} | {more, RestFormat, Nchars, InputStack} | {error, What}</v> <v> InputList = chars()</v> <v> LeftOverChars = string()</v> <v> RestFormat = string()</v> <v> Nchars = int()</v> <v> InputStack = chars()</v> <v> What = term()</v> </type> <desc> <p>Tries to read <c>String</c> in accordance with the control sequences in <c>Format</c>. See <seealso marker="io#fread/3">io:fread/3</seealso> for a detailed description of the available formatting options. It is assumed that <c>String</c> contains whole lines. It returns:</p> <taglist> <tag><c>{ok, InputList, LeftOverChars}</c></tag> <item> <p>The string was read. <c>InputList</c> is the list of successfully matched and read items, and <c>LeftOverChars</c> are the input characters not used.</p> </item> <tag><c>{more, RestFormat, Nchars, InputStack}</c></tag> <item> <p>The string was read, but more input is needed in order to complete the original format string. <c>RestFormat</c> is the remaining format string, <c>NChars</c> the number of characters scanned, and <c>InputStack</c> is the reversed list of inputs matched up to that point.</p> </item> <tag><c>{error, What}</c></tag> <item> <p>The read operation failed and the parameter <c>What</c> gives a hint about the error.</p> </item> </taglist> <p>Example:</p> <pre> 3> <input>io_lib:fread("~f~f~f", "15.6 17.3e-6 24.5").</input> {ok,[15.6,1.73e-5,24.5],[]}</pre> </desc> </func> <func> <name>fread(Continuation, String, Format) -> Return</name> <fsummary>Re-entrant formatted reader</fsummary> <type> <v>Continuation = see below</v> <v>String = Format = string()</v> <v>Return = {done, Result, LeftOverChars} | {more, Continuation}</v> <v> Result = {ok, InputList} | eof | {error, What}</v> <v> InputList = chars()</v> <v> What = term()()</v> <v> LeftOverChars = string()</v> </type> <desc> <p>This is the re-entrant formatted reader. The continuation of the first call to the functions must be <c>[]</c>. Refer to Armstrong, Virding, Williams, 'Concurrent Programming in Erlang', Chapter 13 for a complete description of how the re-entrant input scheme works.</p> <p>The function returns:</p> <taglist> <tag><c>{done, Result, LeftOverChars}</c></tag> <item> <p>The input is complete. The result is one of the following:</p> <taglist> <tag><c>{ok, InputList}</c></tag> <item> <p>The string was read. <c>InputList</c> is the list of successfully matched and read items, and <c>LeftOverChars</c> are the remaining characters.</p> </item> <tag><c>eof</c></tag> <item> <p>End of file has been encountered. <c>LeftOverChars</c> are the input characters not used.</p> </item> <tag><c>{error, What}</c></tag> <item> <p>An error occurred and the parameter <c>What</c> gives a hint about the error.</p> </item> </taglist> </item> <tag><c>{more, Continuation}</c></tag> <item> <p>More data is required to build a term. <c>Continuation</c> must be passed to <c>fread/3</c>, when more data becomes available.</p> </item> </taglist> </desc> </func> <func> <name>write_atom(Atom) -> chars()</name> <fsummary>Write an atom</fsummary> <type> <v>Atom = atom()</v> </type> <desc> <p>Returns the list of characters needed to print the atom <c>Atom</c>.</p> </desc> </func> <func> <name>write_string(String) -> chars()</name> <fsummary>Write a string</fsummary> <type> <v>String = string()</v> </type> <desc> <p>Returns the list of characters needed to print <c>String</c> as a string.</p> </desc> </func> <func> <name>write_char(Integer) -> chars()</name> <fsummary>Write a character</fsummary> <type> <v>Integer = int()</v> </type> <desc> <p>Returns the list of characters needed to print a character constant in the ISO-latin-1 character set.</p> </desc> </func> <func> <name>indentation(String, StartIndent) -> int()</name> <fsummary>Indentation after printing string</fsummary> <type> <v>String = string()</v> <v>StartIndent = int()</v> </type> <desc> <p>Returns the indentation if <c>String</c> has been printed, starting at <c>StartIndent</c>.</p> </desc> </func> <func> <name>char_list(Term) -> bool()</name> <fsummary>Test for a list of characters</fsummary> <type> <v>Term = term()</v> </type> <desc> <p>Returns <c>true</c> if <c>Term</c> is a flat list of characters in the ISO-latin-1 range, otherwise it returns <c>false</c>.</p> </desc> </func> <func> <name>deep_char_list(Term) -> bool()</name> <fsummary>Test for a deep list of characters</fsummary> <type> <v>Term = term()</v> </type> <desc> <p>Returns <c>true</c> if <c>Term</c> is a, possibly deep, list of characters in the ISO-latin-1 range, otherwise it returns <c>false</c>.</p> </desc> </func> <func> <name>printable_list(Term) -> bool()</name> <fsummary>Test for a list of printable ISO-latin-1 characters</fsummary> <type> <v>Term = term()</v> </type> <desc> <p>Returns <c>true</c> if <c>Term</c> is a flat list of printable ISO-latin-1 characters, otherwise it returns <c>false</c>.</p> </desc> </func> </funcs> </erlref>