JavaScript

Read Text at a 64-bit Offset from a Remote SFTP File

Demonstrates the Chilkat SFtp.ReadFileText64 method, which reads up to a number of bytes from a specific 64-bit byte offset of an open handle and decodes them to text. The arguments are the handle, the offset, the maximum number of bytes, and the charset. The 64-bit offset supports very large files.

Background: This is the large-file counterpart to reading at a 32-bit offset: use it whenever the position you need lies beyond the ~4 GB reach of a 32-bit integer, for example seeking into a multi-gigabyte archive or database file. Everything else about the read is the same.

Note

This example is intended for running within a Chilkat.Js embedded JavaScript engine. All Chilkat JavaScript examples require Chilkat v11.4.0 or greater.

JavaScript

var success = false;

//  Demonstrates the SFtp.ReadFileText64 method, which reads up to a number of bytes from a
//  specific 64-bit byte offset of an open handle and decodes them to text.  The 1st argument is
//  the handle, the 2nd is the offset, the 3rd is the maximum number of bytes, and the 4th is the
//  charset.  The 64-bit offset supports very large files.

var sftp = new CkSFtp();

//  Connect, authenticate, and initialize the SFTP subsystem.
var port = 22;
success = sftp.Connect("sftp.example.com",port);
if (success == false) {
    console.log(sftp.LastErrorText);
    return;
}

//  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.
var password = "mySshPassword";

success = sftp.AuthenticatePw("mySshLogin",password);
if (success == false) {
    console.log(sftp.LastErrorText);
    return;
}

success = sftp.InitializeSftp();
if (success == false) {
    console.log(sftp.LastErrorText);
    return;
}

var handle = sftp.OpenFile("subdir/hugefile.dat","readOnly","openExisting");
if (sftp.LastMethodSuccess == false) {
    console.log(sftp.LastErrorText);
    return;
}

//  Read 6 bytes starting at a byte offset beyond the 32-bit (4 GB) range.
var offset = 5000000000;
var numBytes = 6;
var text = sftp.ReadFileText64(handle,offset,numBytes,"utf-8");
if (sftp.LastMethodSuccess == false) {
    console.log(sftp.LastErrorText);
    return;
}

console.log(text);

success = sftp.CloseHandle(handle);
if (success == false) {
    console.log(sftp.LastErrorText);
    return;
}

sftp.Disconnect();