Lianja

Write Text at a 32-bit Offset in a Remote SFTP File

Demonstrates the Chilkat SFtp.WriteFileText32 method, which encodes text and writes it at a specific 32-bit byte offset in an open handle. The arguments are the handle, the offset, the charset, and the text.

Background: Explicit-offset writes enable random access — patching a fixed-length record in place, for instance, without rewriting the whole file. The offset is a byte position, not a character position, so with a variable-width encoding like UTF-8 you must account for the encoded size of preceding characters to land where you intend. After the write, the sequential position continues just past the bytes written.

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llSuccess = .F.

//  Demonstrates the SFtp.WriteFileText32 method, which encodes text and writes it at a specific
//  32-bit byte offset in an open handle.  The 1st argument is the handle, the 2nd is the offset,
//  the 3rd is the charset, and the 4th is the text.

loSftp = createobject("CkSFtp")

//  Connect, authenticate, and initialize the SFTP subsystem.
lnPort = 22
llSuccess = loSftp.Connect("sftp.example.com",lnPort)
if (llSuccess = .F.) then
    ? loSftp.LastErrorText
    release loSftp
    return
endif

//  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.
lcPassword = "mySshPassword"

llSuccess = loSftp.AuthenticatePw("mySshLogin",lcPassword)
if (llSuccess = .F.) then
    ? loSftp.LastErrorText
    release loSftp
    return
endif

llSuccess = loSftp.InitializeSftp()
if (llSuccess = .F.) then
    ? loSftp.LastErrorText
    release loSftp
    return
endif

//  Open the remote file for read/write so an existing file can be modified in place.
lcHandle = loSftp.OpenFile("subdir/record.dat","readWrite","openOrCreate")
if (loSftp.LastMethodSuccess = .F.) then
    ? loSftp.LastErrorText
    release loSftp
    return
endif

//  Overwrite 5 bytes starting at offset 10.  The offset is a byte position, not a character
//  position, so it must account for the encoded size of any multibyte characters.
lnOffset = 10
llSuccess = loSftp.WriteFileText32(lcHandle,lnOffset,"utf-8","HELLO")
if (llSuccess = .F.) then
    ? loSftp.LastErrorText
    release loSftp
    return
endif

llSuccess = loSftp.CloseHandle(lcHandle)
if (llSuccess = .F.) then
    ? loSftp.LastErrorText
    release loSftp
    return
endif

? "Wrote at the specified offset."

loSftp.Disconnect()


release loSftp