diff options
Diffstat (limited to 'lib/stdlib/doc/src/io.xml')
| -rw-r--r-- | lib/stdlib/doc/src/io.xml | 109 |
1 files changed, 77 insertions, 32 deletions
diff --git a/lib/stdlib/doc/src/io.xml b/lib/stdlib/doc/src/io.xml index 64fcf4379f..f1037ec76b 100644 --- a/lib/stdlib/doc/src/io.xml +++ b/lib/stdlib/doc/src/io.xml @@ -137,11 +137,11 @@ Hello world! ok</pre> <p>The general format of a control sequence is <c>~F.P.PadModC</c>.</p> - <p>Character <c>C</c> determines the type of control sequence - to be used, <c>F</c> and <c>P</c> are optional numeric - arguments. If <c>F</c>, <c>P</c>, or <c>Pad</c> is <c>*</c>, - the next argument in <c>Data</c> is used as the numeric value - of <c>F</c> or <c>P</c>.</p> + <p>The character <c>C</c> determines the type of control sequence + to be used. It is the only required field. All of <c>F</c>, + <c>P</c>, <c>Pad</c>, and <c>Mod</c> are optional. For example, + to use a <c>#</c> for <c>Pad</c> but use the default values for + <c>F</c> and <c>P</c>, you can write <c>~..#C</c>.</p> <list type="bulleted"> <item> <p><c>F</c> is the <c>field width</c> of the printed argument. A @@ -167,13 +167,26 @@ ok</pre> The default padding character is <c>' '</c> (space).</p> </item> <item> - <p><c>Mod</c> is the control sequence modifier. It is either a - single character (<c>t</c>, for Unicode - translation, and <c>l</c>, for stopping <c>p</c> and - <c>P</c> from detecting printable characters) - that changes the interpretation of <c>Data</c>.</p> + <p><c>Mod</c> is the control sequence modifier. This is + one or more characters that change the interpretation of + <c>Data</c>. The current modifiers are <c>t</c>, for Unicode + translation, and <c>l</c>, for stopping <c>p</c> and <c>P</c> + from detecting printable characters.</p> </item> </list> + <p>If <c>F</c>, <c>P</c>, or <c>Pad</c> is a <c>*</c> character, + the next argument in <c>Data</c> is used as the value. + For example:</p> + <pre> +1> <input>io:fwrite("~*.*.0f~n",[9, 5, 3.14159265]).</input> +003.14159 +ok</pre> + <p>To use a literal <c>*</c> character as <c>Pad</c>, it must be + passed as an argument:</p> + <pre> +2> <input>io:fwrite("~*.*.*f~n",[9, 5, $*, 3.14159265]).</input> +**3.14159 +ok</pre> <p><em>Available control sequences:</em></p> <taglist> <tag><c>~</c></tag> @@ -257,8 +270,9 @@ ok</pre> \x{400} ok 5> <input>io:fwrite("~s~n",[[1024]]).</input> -** exception exit: {badarg,[{io,format,[<0.26.0>,"~s~n",[[1024]]]}, - ...</pre> +** exception error: bad argument + in function io:format/3 + called as io:format(<0.53.0>,"~s~n",[[1024]])</pre> </item> <tag><c>w</c></tag> <item> @@ -276,10 +290,9 @@ ok <c>~w</c>, but breaks terms whose printed representation is longer than one line into many lines and indents each line sensibly. Left-justification is not supported. - It also tries to detect lists of - printable characters and to output these as strings. The - Unicode translation modifier is used for determining - what characters are printable, for example:</p> + It also tries to detect flat lists of + printable characters and output these as strings. + For example:</p> <pre> 1> <input>T = [{attributes,[[{id,age,1.50000},{mode,explicit},</input> <input>{typename,"INTEGER"}], [{id,cho},{mode,explicit},{typename,'Cho'}]]},</input> @@ -301,7 +314,7 @@ ok {mode,implicit}] ok</pre> <p>The field width specifies the maximum line length. - Defaults to 80. The precision specifies the initial + It defaults to 80. The precision specifies the initial indentation of the term. It defaults to the number of characters printed on this line in the <em>same</em> call to <seealso marker="#write/1"><c>write/1</c></seealso> or @@ -331,18 +344,53 @@ ok [{a,[97]}, {b,[98]}] ok</pre> - <p>Binaries that look like UTF-8 encoded strings are - output with the string syntax if the Unicode translation - modifier is specified:</p> + <p>The Unicode translation modifier <c>t</c> specifies how to treat + characters outside the Latin-1 range of codepoints, in + atoms, strings, and binaries. For example, printing an atom + containing a character > 255:</p> + <pre> +8> <input>io:fwrite("~p~n",[list_to_atom([1024])]).</input> +'\x{400}' +ok +9> <input>io:fwrite("~tp~n",[list_to_atom([1024])]).</input> +'Ѐ' +ok</pre> + <p>By default, Erlang only detects lists of characters + in the Latin-1 range as strings, but the <c>+pc unicode</c> + flag can be used to change this (see <seealso + marker="#printable_range/0"> + <c>printable_range/0</c></seealso> for details). For example:</p> + <pre> +10> <input>io:fwrite("~p~n",[[214]]).</input> +"Ö" +ok +11> <input>io:fwrite("~p~n",[[1024]]).</input> +[1024] +ok +12> <input>io:fwrite("~tp~n",[[1024]]).</input> +[1024] +ok +</pre> + <p>but if Erlang was started with <c>+pc unicode</c>:</p> <pre> -9> <input>io:fwrite("~p~n",[[1024]]).</input> +13> <input>io:fwrite("~p~n",[[1024]]).</input> [1024] -10> <input>io:fwrite("~tp~n",[[1024]]).</input> -"\x{400}" -11> <input>io:fwrite("~tp~n", [<<128,128>>]).</input> +ok +14> <input>io:fwrite("~tp~n",[[1024]]).</input> +"Ѐ" +ok</pre> + <p>Similarly, binaries that look like UTF-8 encoded strings + are output with the binary string syntax if the <c>t</c> + modifier is specified:</p> + <pre> +15> <input>io:fwrite("~p~n", [<<208,128>>]).</input> +<<208,128>> +ok +16> <input>io:fwrite("~tp~n", [<<208,128>>]).</input> +<<"Ѐ"/utf8>> +ok +17> <input>io:fwrite("~tp~n", [<<128,128>>]).</input> <<128,128>> -12> <input>io:fwrite("~tp~n", [<<208,128>>]).</input> -<<"\x{400}"/utf8>> ok</pre> </item> <tag><c>W</c></tag> @@ -454,12 +502,9 @@ ok</pre> abc def 'abc def' {foo,1} A ok 2> <input>io:fwrite("~s", [65]).</input> -** exception exit: {badarg,[{io,format,[<0.22.0>,"~s","A"]}, - {erl_eval,do_apply,5}, - {shell,exprs,6}, - {shell,eval_exprs,6}, - {shell,eval_loop,3}]} - in function io:o_request/2</pre> +** exception error: bad argument + in function io:format/3 + called as io:format(<0.53.0>,"~s","A")</pre> <p>In this example, an attempt was made to output the single character 65 with the aid of the string formatting directive <c>"~s"</c>.</p> |