Writes the data with standard syntax in the same way as ~w
, 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 flat lists of printable characters and output these as strings. For example:
1> T = [{attributes,[[{id,age,1.50000},{mode,explicit},
{typename,"INTEGER"}], [{id,cho},{mode,explicit},{typename,'Cho'}]]},
{typename,'Person'},{tag,{'PRIVATE',3}},{mode,implicit}].
...
2> io:fwrite("~w~n", [T]).
[{attributes,[[{id,age,1.5},{mode,explicit},{typename,
[73,78,84,69,71,69,82]}],[{id,cho},{mode,explicit},{typena
me,'Cho'}]]},{typename,'Person'},{tag,{'PRIVATE',3}},{mode
,implicit}]
ok
3> io:fwrite("~62p~n", [T]).
[{attributes,[[{id,age,1.5},
{mode,explicit},
{typename,"INTEGER"}],
[{id,cho},{mode,explicit},{typename,'Cho'}]]},
{typename,'Person'},
{tag,{'PRIVATE',3}},
{mode,implicit}]
ok
The field width specifies the maximum line length. 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 same call to write/1
or format/1,2,3
. For example, using T
above:
4> io:fwrite("Here T = ~62p~n", [T]).
Here T = [{attributes,[[{id,age,1.5},
{mode,explicit},
{typename,"INTEGER"}],
[{id,cho},
{mode,explicit},
{typename,'Cho'}]]},
{typename,'Person'},
{tag,{'PRIVATE',3}},
{mode,implicit}]
ok
As from Erlang/OTP 21.0, a field width of value 0
can be used for specifying that a line is infinitely long, which means that no line breaks are inserted. For example:
5> io:fwrite("~0p~n", [lists:seq(1, 30)]).
[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]
ok
When the modifier l
is specified, no detection of printable character lists takes place, for example:
6> S = [{a,"a"}, {b, "b"}], io:fwrite("~15p~n", [S]).
[{a,"a"},
{b,"b"}]
ok
7> io:fwrite("~15lp~n", [S]).
[{a,[97]},
{b,[98]}]
ok
The Unicode translation modifier t
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:
8> io:fwrite("~p~n",[list_to_atom([1024])]).
'\x{400}'
ok
9> io:fwrite("~tp~n",[list_to_atom([1024])]).
'Ѐ'
ok
By default, Erlang only detects lists of characters in the Latin-1 range as strings, but the +pc unicode
flag can be used to change this (see printable_range/0
for details). For example:
10> io:fwrite("~p~n",[[214]]).
"Ö"
ok
11> io:fwrite("~p~n",[[1024]]).
[1024]
ok
12> io:fwrite("~tp~n",[[1024]]).
[1024]
ok
but if Erlang was started with +pc unicode
:
13> io:fwrite("~p~n",[[1024]]).
[1024]
ok
14> io:fwrite("~tp~n",[[1024]]).
"Ѐ"
ok
Similarly, binaries that look like UTF-8 encoded strings are output with the binary string syntax if the t
modifier is specified:
15> io:fwrite("~p~n", [<<208,128>>]).
<<208,128>>
ok
16> io:fwrite("~tp~n", [<<208,128>>]).
<<"Ѐ"/utf8>>
ok
17> io:fwrite("~tp~n", [<<128,128>>]).
<<128,128>>
ok