Lua

Read Bytes from a Remote SFTP File (BinData)

Demonstrates the Chilkat SFtp.ReadFileBd method, which reads up to a number of bytes from the current position of an open handle and appends them to a BinData. The arguments are the handle, the maximum number of bytes, and the BinData. This example reads in chunks until end-of-file.

Background: For binary files, reading into a BinData preserves the bytes exactly, unlike a text read that decodes through a charset. Because it appends, the chunked read loop accumulates the whole file in the BinData; each pass reads up to the chunk size and the loop repeats until Eof. Fewer bytes than requested can come back near the end of the file, which is normal.

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Lua

local chilkat = require("chilkat")

-- Demonstrates the SFtp.ReadFileBd method, which reads up to a number of bytes from the current
-- position of an open handle and appends them to a BinData.  The 1st argument is the handle, the
-- 2nd is the maximum number of bytes, and the 3rd is the BinData.

local sftp = chilkat.SFtp.new()

-- Connect, authenticate, and initialize the SFTP subsystem.
local port = 22
local success = sftp:connect("sftp.example.com", port)
if not success then
    print(sftp.last_error_text)
    return
end

-- Normally you would not hard-code the password in source.  You should instead obtain it
-- from an interactive prompt, environment variable, or a secrets vault.
local password = "mySshPassword"

success = sftp:authenticate_pw("mySshLogin", password)
if not success then
    print(sftp.last_error_text)
    return
end

success = sftp:initialize_sftp()
if not success then
    print(sftp.last_error_text)
    return
end

local handle = sftp:open_file("subdir/image.png", "readOnly", "openExisting")
if not sftp.last_method_success then
    print(sftp.last_error_text)
    return
end

-- Read the file in chunks until end-of-file, accumulating the bytes in a BinData.
local bd = chilkat.BinData.new()
local chunkSize = 8192
local reading = true
while reading do
    success = sftp:read_file_bd(handle, chunkSize, bd)
    if sftp:last_read_failed(handle) then
        print(sftp.last_error_text)
        return
    end

    reading = not sftp:eof(handle)
end

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

print("Read " .. bd.num_bytes .. " bytes.")

sftp:disconnect()