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Function std.stdio.File.byLine
Returns an input range set up to read from the file handle one line at a time.
auto byLine(Terminator, Char)
(
KeepTerminator keepTerminator = No .keepTerminator,
Terminator terminator = '\x0a'
)
if (isScalarType!Terminator);
auto byLine(Terminator, Char)
(
KeepTerminator keepTerminator,
Terminator terminator
)
if (is(immutable(ElementEncodingType!Terminator) == immutable(Char)));
The element type for the range will be Char[]
. Range primitives
may throw StdioException
on I/O error.
Note
Each front
will not persist after popFront
is called, so the caller must copy its contents (e.g. by
calling to!string
) when retention is needed. If the caller needs
to retain a copy of every line, use the byLineCopy
function
instead.
Parameters
Name | Description |
---|---|
Char | Character type for each line, defaulting to char . |
keepTerminator | Use Yes to include the
terminator at the end of each line. |
terminator | Line separator ('\n' by default). Use
newline for portability (unless the file was opened in
text mode). |
Example
import std .algorithm, std .stdio, std .string;
// Count words in a file using ranges.
void main()
{
auto file = File("file.txt"); // Open for reading
const wordCount = file .byLine() // Read lines
.map!split // Split into words
.map!(a => a .length) // Count words per line
.sum(); // Total word count
writeln(wordCount);
}
Example
import std .range, std .stdio;
// Read lines using foreach.
void main()
{
auto file = File("file.txt"); // Open for reading
auto range = file .byLine();
// Print first three lines
foreach (line; range .take(3))
writeln(line);
// Print remaining lines beginning with '#'
foreach (line; range)
{
if (!line .empty && line[0] == '#')
writeln(line);
}
}
Notice that neither example accesses the line data returned by
front
after the corresponding popFront
call is made (because
the contents may well have changed).
Authors
Walter Bright, Andrei Alexandrescu, Alex Rønne Petersen
License
Copyright © 1999-2022 by the D Language Foundation | Page generated by ddox.