Rust

Receive from an SSH Channel Until a Pattern Matches

Demonstrates the Chilkat Ssh.ChannelReceiveUntilMatch method, which receives text until the accumulated text matches a pattern. The arguments are the channel number, the pattern, the charset, and whether matching is case-sensitive. Existing buffered text is checked before waiting for more network data.

Important: Set the ReadTimeoutMs property before calling this method. It defaults to 0, meaning no limit, so without it the call waits forever if the received data never contains a match.

Background: Driving a shell channel means knowing when the remote side has finished talking. With no PTY requested the shell is non-interactive and never prints a prompt, so the reliable signal is a marker you deliberately echo after your command. This method automates "read until you see X." The pattern syntax is deliberately minimal: literal characters plus *, which matches zero or more characters and can span line breaks. ? and bracket classes are not supported, and backslash does not escape a literal *.

Chilkat Rust Downloads

Download Chilkat for Rust

Rust


// Demonstrates the Ssh.ChannelReceiveUntilMatch method, which receives text until the
// accumulated text matches a pattern.  The 1st argument is the channel number, the 2nd is the
// pattern, the 3rd is the charset, and the 4th selects case-sensitive matching.  The pattern
// supports literal characters plus "*", which matches zero or more characters.

let ssh = chilkat::Ssh::new();

let ssh_port = 22;
if ssh.connect("ssh.example.com", ssh_port).is_err() {
    println!("{}", ssh.last_error_text());
    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.
let password = "mySshPassword".to_string();

if ssh.authenticate_pw("mySshLogin", &password).is_err() {
    println!("{}", ssh.last_error_text());
    return;
}

let channel_num = ssh.open_session_channel();
if channel_num < 0 {
    println!("{}", ssh.last_error_text());
    return;
}

// Start a shell WITHOUT requesting a PTY.  Without a PTY the shell sees it is connected to a
// raw data pipe and enters non-interactive mode: it suppresses the command prompt, does not
// echo typed commands back, and skips interactive login scripts.  The output is therefore
// clean and easily parseable -- but because no prompt is ever sent, code must not wait for
// one.  Instead, have each command print a predictable marker, or wait for EOF / channel close.
if ssh.send_req_shell(channel_num).is_err() {
    println!("{}", ssh.last_error_text());
    return;
}

// There is no prompt to wait for, so make the command itself announce when it has finished
// by echoing a marker after it.
if ssh.channel_send_string(channel_num, "ls -l /tmp; echo DONE_MARKER\n", "utf-8").is_err() {
    println!("{}", ssh.last_error_text());
    return;
}

// IMPORTANT: Set a read timeout before receiving until a match.  ReadTimeoutMs defaults to 0,
// which means no limit -- without it, this call waits forever if the received data never
// contains a match.
ssh.set_read_timeout_ms(15000);

// Receive until the marker appears in the output.
let case_sensitive = false;
if ssh.channel_receive_until_match(channel_num, "DONE_MARKER", "utf-8", case_sensitive).is_err() {
    println!("{}", ssh.last_error_text());
    return;
}

let Ok(output) = ssh.get_received_text(channel_num, "utf-8") else {
    println!("{}", ssh.last_error_text());
    return;
};

println!("{}", output);

ssh.disconnect();