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version 2.108.0

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Function std.stdio.File.readf

Reads formatted data from the file using std.format.formattedRead.

uint readf(alias format, Data...) (
  auto ref Data data
)
if (isSomeString!(typeof(format)));

uint readf(Data...) (
  scope const(char)[] format,
  auto ref Data data
);

Parameters

NameDescription
format The format string. When passed as a compile-time argument, the string will be statically checked against the argument types passed.
data Items to be read.

Returns

Same as formattedRead: The number of variables filled. If the input range r ends early, this number will be less than the number of variables provided.

Example

// test.d
void main()
{
    import std.stdio;
    auto f = File("input");
    foreach (_; 0 .. 3)
    {
        int a;
        f.readf!" %d"(a);
        writeln(++a);
    }
}

% echo "1 2 3" > input
% rdmd test.d
2
3
4

Example

static import std.file;

auto deleteme = std.file.deleteme();
write(deleteme, "hello\nworld\ntrue\nfalse\n");
scope(exit) remove(deleteme);
string s;
auto f = File(deleteme);
f.readf!"%s\n"(s);
writeln(s); // "hello"
f.readf("%s\n", s);
writeln(s); // "world"

bool b1, b2;
f.readf("%s\n%s\n", b1, b2);
assert(b1 == true && b2 == false);

Authors

Walter Bright, Andrei Alexandrescu, Alex Rønne Petersen

License

Boost License 1.0.