io_lib(3erl) Erlang Module Definition io_lib(3erl)
NAME
io_lib - I/O library functions.
DESCRIPTION
This module contains functions for converting to and from strings
(lists of characters). They are used for implementing the functions in
the io module. There is no guarantee that the character lists returned
from some of the functions are flat, they can be deep lists. Function
lists:flatten/1 can be used for flattening deep lists.
DATA TYPES
chars() = [char() | chars()]
continuation()
A continuation as returned by fread/3.
chars_limit() = integer()
depth() = -1 | integer() >= 0
fread_error() =
atom | based | character | float | format | input | integer |
string | unsigned
fread_item() = string() | atom() | integer() | float()
latin1_string() = [unicode:latin1_char()]
format_spec() =
#{control_char := char(),
args := [any()],
width := none | integer(),
adjust := left | right,
precision := none | integer(),
pad_char := char(),
encoding := unicode | latin1,
strings := boolean()}
Where:
* control_char is the type of control sequence: $P, $w, and so
on.
* args is a list of the arguments used by the control se-
quence, or an empty list if the control sequence does not
take any arguments.
* width is the field width.
* adjust is the adjustment.
* precision is the precision of the printed argument.
* pad_char is the padding character.
* encoding is set to true if translation modifier t is
present.
* strings is set to false if modifier l is present.
EXPORTS
build_text(FormatList) -> chars()
Types:
FormatList = [char() | format_spec()]
For details, see scan_format/2.
char_list(Term) -> boolean()
Types:
Term = term()
Returns true if Term is a flat list of characters in the Unicode
range, otherwise false.
deep_char_list(Term) -> boolean()
Types:
Term = term()
Returns true if Term is a, possibly deep, list of characters in
the Unicode range, otherwise false.
deep_latin1_char_list(Term) -> boolean()
Types:
Term = term()
Returns true if Term is a, possibly deep, list of characters in
the ISO Latin-1 range, otherwise false.
format(Format, Data) -> chars()
fwrite(Format, Data) -> chars()
Types:
Format = io:format()
Data = [term()]
Returns a character list that represents Data formatted in ac-
cordance with Format. For a detailed description of the avail-
able formatting options, see io:fwrite/1,2,3. If the format
string or argument list contains an error, a fault is generated.
If and only if the Unicode translation modifier is used in the
format string (that is, ~ts or ~tc), the resulting list can con-
tain characters beyond the ISO Latin-1 character range (that is,
numbers > 255). If so, the result is still an ordinary Erlang
string(), and can well be used in any context where Unicode data
is allowed.
format(Format, Data, Options) -> chars()
fwrite(Format, Data, Options) -> chars()
Types:
Format = io:format()
Data = [term()]
Options = [Option]
Option = {chars_limit, CharsLimit}
CharsLimit = chars_limit()
Returns a character list that represents Data formatted in ac-
cordance with Format in the same way as fwrite/2 and format/2,
but takes an extra argument, a list of options.
Valid option:
{chars_limit, CharsLimit}:
A soft limit on the number of characters returned. When the
number of characters is reached, remaining structures are
replaced by "...". CharsLimit defaults to -1, which means no
limit on the number of characters returned.
fread(Format, String) -> Result
Types:
Format = String = string()
Result =
{ok, InputList :: [fread_item()], LeftOverChars ::
string()} |
{more,
RestFormat :: string(),
Nchars :: integer() >= 0,
InputStack :: chars()} |
{error, {fread, What :: fread_error()}}
Tries to read String in accordance with the control sequences in
Format. For a detailed description of the available formatting
options, see io:fread/3. It is assumed that String contains
whole lines.
The function returns:
{ok, InputList, LeftOverChars}:
The string was read. InputList is the list of successfully
matched and read items, and LeftOverChars are the input
characters not used.
{more, RestFormat, Nchars, InputStack}:
The string was read, but more input is needed to complete
the original format string. RestFormat is the remaining for-
mat string, Nchars is the number of characters scanned, and
InputStack is the reversed list of inputs matched up to that
point.
{error, What}:
The read operation failed and parameter What gives a hint
about the error.
Example:
3> io_lib:fread("~f~f~f", "15.6 17.3e-6 24.5").
{ok,[15.6,1.73e-5,24.5],[]}
fread(Continuation, CharSpec, Format) -> Return
Types:
Continuation = continuation() | []
CharSpec = string() | eof
Format = string()
Return =
{more, Continuation1 :: continuation()} |
{done, Result, LeftOverChars :: string()}
Result =
{ok, InputList :: [fread_item()]} |
eof |
{error, {fread, What :: fread_error()}}
This is the re-entrant formatted reader. The continuation of the
first call to the functions must be []. For a complete descrip-
tion of how the re-entrant input scheme works, see Armstrong,
Virding, Williams: 'Concurrent Programming in Erlang', Chapter
13.
The function returns:
{done, Result, LeftOverChars}:
The input is complete. The result is one of the following:
{ok, InputList}:
The string was read. InputList is the list of successfully
matched and read items, and LeftOverChars are the remain-
ing characters.
eof:
End of file was encountered. LeftOverChars are the input
characters not used.
{error, What}:
An error occurred and parameter What gives a hint about
the error.
{more, Continuation}:
More data is required to build a term. Continuation must be
passed to fread/3 when more data becomes available.
indentation(String, StartIndent) -> integer()
Types:
String = string()
StartIndent = integer()
Returns the indentation if String has been printed, starting at
StartIndent.
latin1_char_list(Term) -> boolean()
Types:
Term = term()
Returns true if Term is a flat list of characters in the ISO
Latin-1 range, otherwise false.
nl() -> string()
Returns a character list that represents a new line character.
print(Term) -> chars()
print(Term, Column, LineLength, Depth) -> chars()
Types:
Term = term()
Column = LineLength = integer() >= 0
Depth = depth()
Returns a list of characters that represents Term, but breaks
representations longer than one line into many lines and indents
each line sensibly. Also tries to detect and output lists of
printable characters as strings.
* Column is the starting column; defaults to 1.
* LineLength is the maximum line length; defaults to 80.
* Depth is the maximum print depth; defaults to -1, which
means no limitation.
printable_latin1_list(Term) -> boolean()
Types:
Term = term()
Returns true if Term is a flat list of printable ISO Latin-1
characters, otherwise false.
printable_list(Term) -> boolean()
Types:
Term = term()
Returns true if Term is a flat list of printable characters,
otherwise false.
What is a printable character in this case is determined by
startup flag +pc to the Erlang VM; see io:printable_range/0 and
erl(1).
printable_unicode_list(Term) -> boolean()
Types:
Term = term()
Returns true if Term is a flat list of printable Unicode charac-
ters, otherwise false.
scan_format(Format, Data) -> FormatList
Types:
Format = io:format()
Data = [term()]
FormatList = [char() | format_spec()]
Returns a list corresponding to the specified format string,
where control sequences have been replaced with corresponding
tuples. This list can be passed to:
* build_text/1 to have the same effect as format(Format, Args)
* unscan_format/1 to get the corresponding pair of Format and
Args (with every * and corresponding argument expanded to
numeric values)
A typical use of this function is to replace unbounded-size con-
trol sequences like ~w and ~p with the depth-limited variants ~W
and ~P before formatting to text in, for example, a logger.
unscan_format(FormatList) -> {Format, Data}
Types:
FormatList = [char() | format_spec()]
Format = io:format()
Data = [term()]
For details, see scan_format/2.
write(Term) -> chars()
write(Term, Depth) -> chars()
write(Term, Options) -> chars()
Types:
Term = term()
Options = [Option]
Option =
{chars_limit, CharsLimit} |
{depth, Depth} |
{encoding, latin1 | utf8 | unicode}
CharsLimit = chars_limit()
Depth = depth()
Returns a character list that represents Term. Option Depth con-
trols the depth of the structures written. When the specified
depth is reached, everything below this level is replaced by
"...". Depth defaults to -1, which means no limitation. Option
CharsLimit puts a soft limit on the number of characters re-
turned. When the number of characters is reached, remaining
structures are replaced by "...". CharsLimit defaults to -1,
which means no limit on the number of characters returned.
Example:
1> lists:flatten(io_lib:write({1,[2],[3],[4,5],6,7,8,9})).
"{1,[2],[3],[4,5],6,7,8,9}"
2> lists:flatten(io_lib:write({1,[2],[3],[4,5],6,7,8,9}, 5)).
"{1,[2],[3],[...],...}"
3> lists:flatten(io_lib:write({[1,2,3],[4,5],6,7,8,9}, [{chars_limit,20}])).
"{[1,2|...],[4|...],...}"
write_atom(Atom) -> chars()
Types:
Atom = atom()
Returns the list of characters needed to print atom Atom.
write_atom_as_latin1(Atom) -> latin1_string()
Types:
Atom = atom()
Returns the list of characters needed to print atom Atom. Non-
Latin-1 characters are escaped.
write_char(Char) -> chars()
Types:
Char = char()
Returns the list of characters needed to print a character con-
stant in the Unicode character set.
write_char_as_latin1(Char) -> latin1_string()
Types:
Char = char()
Returns the list of characters needed to print a character con-
stant in the Unicode character set. Non-Latin-1 characters are
escaped.
write_latin1_char(Latin1Char) -> latin1_string()
Types:
Latin1Char = unicode:latin1_char()
Returns the list of characters needed to print a character con-
stant in the ISO Latin-1 character set.
write_latin1_string(Latin1String) -> latin1_string()
Types:
Latin1String = latin1_string()
Returns the list of characters needed to print Latin1String as a
string.
write_string(String) -> chars()
Types:
String = string()
Returns the list of characters needed to print String as a
string.
write_string_as_latin1(String) -> latin1_string()
Types:
String = string()
Returns the list of characters needed to print String as a
string. Non-Latin-1 characters are escaped.
Ericsson AB stdlib 3.13 io_lib(3erl)