method Deno.FsFile.prototype.seek
FsFile.prototype.seek(offset: number | bigint,whence: SeekMode,): Promise<number>
Seek to the given offset under mode given by whence. The call
resolves to the new position within the resource (bytes from the start).
// Given the file contains "Hello world" text, which is 11 bytes long:
using file = await Deno.open(
"hello.txt",
{ read: true, write: true, truncate: true, create: true },
);
await file.write(new TextEncoder().encode("Hello world"));
// advance cursor 6 bytes
const cursorPosition = await file.seek(6, Deno.SeekMode.Start);
console.log(cursorPosition); // 6
const buf = new Uint8Array(100);
await file.read(buf);
console.log(new TextDecoder().decode(buf)); // "world"
The seek modes work as follows:
// Given the file contains "Hello world" text, which is 11 bytes long:
const file = await Deno.open(
"hello.txt",
{ read: true, write: true, truncate: true, create: true },
);
await file.write(new TextEncoder().encode("Hello world"));
// Seek 6 bytes from the start of the file
console.log(await file.seek(6, Deno.SeekMode.Start)); // "6"
// Seek 2 more bytes from the current position
console.log(await file.seek(2, Deno.SeekMode.Current)); // "8"
// Seek backwards 2 bytes from the end of the file
console.log(await file.seek(-2, Deno.SeekMode.End)); // "9" (i.e. 11-2)
whence: SeekMode
Promise<number>