The following command uploads the first part in a multipart upload initiated with the create-multipart-upload command:

aws s3api upload-part --bucket my-bucket --key 'multipart/01' --part-number 1 --body part01 --upload-id  "dfRtDYU0WWCCcH43C3WFbkRONycyCpTJJvxu2i5GYkZljF.Yxwh6XG7WfS2vC4to6HiV6Yjlx.cph0gtNBtJ8P3URCSbB7rjxI5iEwVDmgaXZOGgkk5nVTW16HOQ5l0R"

The body option takes the name or path of a local file for upload (do not use the file:// prefix). The minimum part size is 5 MB. Upload ID is returned by create-multipart-upload and can also be retrieved with list-multipart-uploads. Bucket and key are specified when you create the multipart upload.

Output:

{
    "ETag": "\"e868e0f4719e394144ef36531ee6824c\""
}

Save the ETag value of each part for later. They are required to complete the multipart upload.