Lua

Check if a Remote File or Directory Exists

Demonstrates the Chilkat SFtp.FileExists method, which checks a remote path and returns an integer describing what is there. The first argument is the remote path and the second (followLinks) selects whether a symbolic link is followed to its target. The return value is -1 on error, 0 if nothing exists, 1 for a file, 2 for a directory, 3 for a symbolic link, and higher values for special entry types.

Background: This returns more than a yes/no because "does it exist" usually comes with "and is it the kind of thing I expect" — a job that means to write a file should notice if a directory already occupies the path. The followLinks flag decides whether a symbolic link is reported as a link (3, only when not following) or transparently resolved to its target's type. Always handle the -1 case: it means the check itself failed, which is different from the path not existing.

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Lua

local chilkat = require("chilkat")

-- Demonstrates the SFtp.FileExists method, which checks a remote path and returns an integer
-- describing what is there.  The 1st argument is the remote path and the 2nd (followLinks)
-- selects whether a symbolic link is followed to its target.

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

-- When followLinks is true, a symbolic link is followed and the target's type is returned.
local followLinks = true
local result = sftp:file_exists("subdir/report.pdf", followLinks)

-- Interpret the return value.
if result == (-1) then
    print(sftp.last_error_text)
    return
end

if result == 0 then
    print("The path does not exist.")
end

if result == 1 then
    print("A regular file exists.")
end

if result == 2 then
    print("A directory exists.")
end

-- Other possible values: 3 = symbolic link (only when followLinks is false), 4 = special
-- entry, 5 = unknown, 6 = socket, 7 = character device, 8 = block device, 9 = FIFO.

sftp:disconnect()