CODEWITHSUNDEEP
zig
kezzos
kezzos

Reputation: 3221

How to read stdin in zig

I'm trying to read a file from stdin in zig but my approach seems a bit slow. So far I have:

var reader = std.io.getStdIn().reader();
var count: u32 = 0;
var buf: [1000]u8 = undefined;
while (try reader.readUntilDelimiterOrEof(&buf, '\n')) |line| {
    _ = line;
    count += 1;
}

Ive tried compiling with zig build -Doptimize=ReleaseFast, however reading a 10k line file using less test.sam | time zig-test takes around 1.2s, whilst using less test.sam | time wc -l takes 0.04s. Output of time command for zig-test was: 0.52s user 0.72s system 99% cpu 1.254 total Seems to be a lot of time spent in both system call and user.

Reading the file directly using this code reduced the time to a more reasonable 0.12s:

var file = try std.fs.cwd().openFile("test.sam", .{});
defer file.close();
var buf_reader = std.io.bufferedReader(file.reader());
var reader = buf_reader.reader();
var count: u32 = 0;
var buf: [10000]u8 = undefined;
while (try reader.readUntilDelimiterOrEof(&buf, '\n')) |line| {
    _ = line;
    count += 1;
}

Time output was: 0.13s user 0.00s system 98% cpu 0.133 total

Upvotes: 4

Views: 4912

Answers (1)

kristoff
kristoff

Reputation: 642

You want to add buffering probably: https://zig.news/kristoff/how-to-add-buffering-to-a-writer-reader-in-zig-7jd

Upvotes: 1

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