Lua

SFTP Upload Large File in Parts

See more SFTP Examples

Demonstrates how to split a large file into N parts and then upload each part separately. This technique can be used to potentially avoid limits a SFTP server might impose on upload file size. Lua

local chilkat = require("chilkat")

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

local sftp = chilkat.SFtp.new()

-- Set some timeouts, in milliseconds:
sftp.connect_timeout_ms = 5000
sftp.idle_timeout_ms = 10000

-- Connect to the SSH server.
-- The standard SSH port = 22
-- The hostname may be a hostname or IP address.
local hostname = "sftp.example.com"
local port = 22
local success = sftp:connect(hostname, port)
if not success then
    print(sftp.last_error_text)
    return
end

-- Authenticate with the SSH server.  Chilkat SFTP supports
-- both password-based authenication as well as public-key
-- authentication.  This example uses password authenication.
success = sftp:authenticate_pw("myLogin", "myPassword")
if not success then
    print(sftp.last_error_text)
    return
end

-- After authenticating, the SFTP subsystem must be initialized:
success = sftp:initialize_sftp()
if not success then
    print(sftp.last_error_text)
    return
end

-- Open a remote file for writing on the SSH server.
-- If the file already exists, it is overwritten.
-- (Specify "createNew" instead of "createTruncate" to
-- prevent overwriting existing files.)
local handle = sftp:open_file("big.zip", "writeOnly", "createTruncate")
if not sftp.last_method_success then
    print(sftp.last_error_text)
    return
end

-- We're going to upload the local file "qa_data/zips/big.zip" (a relative local path from our current working directory)
-- to the SFTP server.
local localFilePath = "qa_data/zips/big.zip"

-- Rather than uploading in one shot, we'll read the local file in chunks
-- and upload a chunk at a time.
local fac = chilkat.FileAccess.new()

success = fac:open_for_read(localFilePath)
if not success then
    sftp:close_handle(handle)
    print(fac.last_error_text)
    return
end

-- If we were to split the local file into 128K chunks, how many chunks (blocks) would
-- we have, including the last partial block?
local blockSize = 131072
local numBlocks = fac:get_num_blocks(blockSize)
print("Number of blocks = " .. numBlocks)

local bd = chilkat.BinData.new()
local i = 0
while i < numBlocks do
    -- Read the Nth block, which gets appended to the bd.  (which means
    -- we must clear the contents of bd before the next iteration)
    success = fac:read_block_bd(i, blockSize, bd)
    if not success then
        sftp:close_handle(handle)
        print(fac.last_error_text)
        return
    end

    -- Upload this block to the open remote file.
    success = sftp:write_file_bd(handle, bd)
    if not success then
        print(sftp.last_error_text)
        return
    end

    -- Clear the contents for the next iteration.
    bd:clear()

    i = i + 1
end

-- Close the local file.
fac:file_close()

-- -----------------------------------------------------------------------------
-- This is important.  You must close the handle on the server.
-- Otherwise open handles will accumulate on the server until eventually a limit
-- is reached and the server will fail on a call to OpenFile.
-- -----------------------------------------------------------------------------

-- Close the remote file handle on the server.
success = sftp:close_handle(handle)
if not success then
    print(sftp.last_error_text)
    return
end

print("Success.")