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const std = @import("std");
const log = std.log.scoped(.@"linux-cgroup");
/// Returns the path to the cgroup for the given pid.
pub fn current(buf: []u8, pid: u32) ?[]const u8 {
var path_buf: [std.fs.max_path_bytes]u8 = undefined;
// Read our cgroup by opening /proc/<pid>/cgroup and reading the first
// line. The first line will look something like this:
// 0::/user.slice/user-1000.slice/session-1.scope
// The cgroup path is the third field.
const path = std.fmt.bufPrint(&path_buf, "/proc/{}/cgroup", .{pid}) catch return null;
const file = std.fs.openFileAbsolute(path, .{}) catch return null;
defer file.close();
var read_buf: [64]u8 = undefined;
var file_reader = file.reader(&read_buf);
const reader = &file_reader.interface;
const len = reader.readSliceShort(buf) catch return null;
const contents = buf[0..len];
// Find the last ':'
const idx = std.mem.lastIndexOfScalar(u8, contents, ':') orelse return null;
return std.mem.trimRight(u8, contents[idx + 1 ..], " \r\n");
}
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