Tcl

Get Received SSH Text into a StringBuilder

Demonstrates the Chilkat Ssh.GetReceivedSb method, which decodes a channel's receive buffer and appends the text to a StringBuilder. The arguments are the channel number, the charset, and the StringBuilder. The receive buffer is cleared afterward.

Background: Because this appends rather than replaces, it is the natural choice for accumulating output across repeated reads — call it in a loop and the StringBuilder grows into the complete transcript. It also avoids creating a new string on every retrieval, which matters when a command produces a large amount of text.

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Tcl


load ./chilkat.dll

set success 0

#  Demonstrates the Ssh.GetReceivedSb method, which decodes the channel's receive buffer and
#  appends the text to a StringBuilder.  The 1st argument is the channel number, the 2nd is the
#  charset, and the 3rd is the StringBuilder.  The receive buffer is cleared afterward.

set ssh [new_CkSsh]

set sshPort 22
set success [CkSsh_Connect $ssh "ssh.example.com" $sshPort]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    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 [CkSsh_AuthenticatePw $ssh "mySshLogin" $password]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

set channelNum [CkSsh_OpenSessionChannel $ssh]
if {$channelNum < 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

set success [CkSsh_SendReqExec $ssh $channelNum "ls -l /tmp"]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

#  IMPORTANT: Set a read timeout.  ReadTimeoutMs defaults to 0, which means no limit -- without
#  it, this call waits forever if the server never sends channel close.
CkSsh_put_ReadTimeoutMs $ssh 15000

set success [CkSsh_ChannelReceiveToClose $ssh $channelNum]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

#  Append the received text to a StringBuilder.  Existing content is preserved.
set sb [new_CkStringBuilder]

set success [CkSsh_GetReceivedSb $ssh $channelNum "utf-8" $sb]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    delete_CkStringBuilder $sb
    exit
}

puts "Characters received: [CkStringBuilder_get_Length $sb]"
set output [CkStringBuilder_getAsString $sb]
puts "$output"

CkSsh_Disconnect $ssh

delete_CkSsh $ssh
delete_CkStringBuilder $sb