Tcl

Get the Byte Count of the Last SFTP Read

Demonstrates the Chilkat SFtp.LastReadNumBytes method, which returns the number of bytes received by the most recent read for a handle. The only argument is the handle.

Background: SFTP reads may return fewer bytes than requested even before the end of the file, so knowing the actual count is useful for tracking progress and for advancing an explicit offset by the right amount. Both a normal EOF read and a failed read report 0, so pair this with Eof and LastReadFailed to interpret a zero-byte result correctly.

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Tcl


load ./chilkat.dll

set success 0

#  Demonstrates the SFtp.LastReadNumBytes method, which returns the number of bytes received by
#  the most recent read for a handle.  The only argument is the handle.

set sftp [new_CkSFtp]

#  Connect, authenticate, and initialize the SFTP subsystem.
set port 22
set success [CkSFtp_Connect $sftp "sftp.example.com" $port]
if {$success == 0} then {
    puts [CkSFtp_lastErrorText $sftp]
    delete_CkSFtp $sftp
    exit
}

#  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.
set password "mySshPassword"

set success [CkSFtp_AuthenticatePw $sftp "mySshLogin" $password]
if {$success == 0} then {
    puts [CkSFtp_lastErrorText $sftp]
    delete_CkSFtp $sftp
    exit
}

set success [CkSFtp_InitializeSftp $sftp]
if {$success == 0} then {
    puts [CkSFtp_lastErrorText $sftp]
    delete_CkSFtp $sftp
    exit
}

set handle [CkSFtp_openFile $sftp "subdir/data.txt" "readOnly" "openExisting"]
if {[CkSFtp_get_LastMethodSuccess $sftp] == 0} then {
    puts [CkSFtp_lastErrorText $sftp]
    delete_CkSFtp $sftp
    exit
}

set bd [new_CkBinData]

set chunkSize 4096
set reading 1
while {$reading} {
    set success [CkSFtp_ReadFileBd $sftp $handle $chunkSize $bd]
    if {CkSFtp_LastReadFailed $sftp $handle} then {
        puts [CkSFtp_lastErrorText $sftp]
        delete_CkSFtp $sftp
        delete_CkBinData $bd
        exit
    }

    #  Report how many bytes the last read actually returned.  A normal EOF read reports 0.
    set lastCount [CkSFtp_LastReadNumBytes $sftp $handle]
    puts "Last read returned $lastCount bytes."

    set reading ![CkSFtp_Eof $sftp $handle]
}

set success [CkSFtp_CloseHandle $sftp $handle]
if {$success == 0} then {
    puts [CkSFtp_lastErrorText $sftp]
    delete_CkSFtp $sftp
    delete_CkBinData $bd
    exit
}

puts "Total: [CkBinData_get_NumBytes $bd] bytes."

CkSFtp_Disconnect $sftp

delete_CkSFtp $sftp
delete_CkBinData $bd