Zig

S3 Get Object Metadata, such as ETag

See more Amazon S3 (new) Examples

Demonstrates how to get an S3 object's metadata using a HEAD request. Zig

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    const rest = try chilkat.Rest.init();
    defer rest.deinit();

    // Connect to the Amazon AWS REST server in the desired region.
    // In this case we connect to S3 in the "us-west-2" region.
    const b_tls = true;
    const port = 443;
    const b_auto_reconnect = true;
    try rest.connect("s3-us-west-2.amazonaws.com", port, b_tls, b_auto_reconnect);

    // Provide AWS credentials.
    const auth_aws = try chilkat.AuthAws.init();
    defer auth_aws.deinit();
    auth_aws.setAccessKey("AWS_ACCESS_KEY");
    auth_aws.setSecretKey("AWS_SECRET_KEY");
    auth_aws.setServiceName("s3");

    // This particular bucket is in the Oregon region, as opposed to the US Standard,
    // therefore the Region must be set appropriately.
    // Also note that we connected to "s3-us-west-2.amazonaws.com".
    auth_aws.setRegion("us-west-2");

    try rest.setAuthAws(auth_aws);

    // Note: The above REST connection and setup of the AWS credentials
    // can be done once.  After connecting, any number of REST calls can be made.
    // The "auto reconnect" property passed to rest.Connect indicates that if
    // the connection is lost, a REST method call will automatically reconnect
    // if needed.
    // --------------------------------------------------------------------------

    // Set the bucket name via the HOST header.
    // In this case, the bucket name is "chilkat.ocean".
    // Note that the Host header should use "bucketName.s3.amazonaws.com", not "bucketName.s3-us-west-2.amazonaws.com"
    rest.setHost("chilkat.ocean.s3.amazonaws.com");

    // Our object is "starfish.jpg".
    // Get the metadata.
    // Since we are sending a HEAD request, we shouldn't use any of the Full* methods.
    // Instead, send the request, then just read the response header.
    rest.sendReqNoBody("HEAD", "/starfish.jpg") catch {
        std.debug.print("{s}\n", .{try rest.getLastErrorText(alloc)});
        return;
    };

    // Now get the response header.
    const status_code = rest.readResponseHeader();
    if (status_code < 0) {
        std.debug.print("{s}\n", .{try rest.getLastErrorText(alloc)});
        return;
    }

    // When successful, the S3 Storage service will respond with a 200 response code,
    // with an XML body.
    if (status_code != 200) {
        // Examine the request/response to see what happened.
        std.debug.print("response status code = {d}\n", .{status_code});
        std.debug.print("response status text = {s}\n", .{try rest.getResponseStatusText(alloc)});
        std.debug.print("response header: {s}\n", .{try rest.getResponseHeader(alloc)});
        return;
    }

    // The response header contains information about the S3 object.
    // For example:

    //     HTTP/1.1 200 OK
    //     x-amz-id-2: GrV/hrB2EUkBlWc0h3JDdmVIrYDXfPC7CGvo/qSVRmYRPwilAOry8+4r2YWl4xJfa1HRYXrP808=
    //     x-amz-request-id: 4BDC6D6AEA0BDEF3
    //     Date: Mon, 13 May 2019 22:03:13 GMT
    //     Last-Modified: Mon, 10 Nov 2014 16:10:23 GMT
    //     ETag: "2e9c59dbf2662367dc97dfdda85da048"
    //     Accept-Ranges: bytes
    //     Content-Type: image/jpg
    //     Content-Length: 6229
    //     Server: AmazonS3

    // Get the ETag response header value:
    const etag = try rest.responseHdrByName(alloc, "ETag");
    std.debug.print("ETag: {s}\n", .{etag});
}