SSH to a Cisco Switch - Processing "More" Responses

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Demonstrates connecting to a Cisco switch, entering privileged mode with the ena command, and running a command whose response is paged. Each page ends with --More-- and requires a SPACE character to request the next page.

Note: QuickShell allocates a PTY, which is what a network device console expects. The device presents an interactive prompt, and each command's output is read up to the next prompt.

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // Demonstrates connecting to a Cisco switch, entering privileged mode, and running a command
    // whose response is paged -- each page ends with "--More--" and requires a SPACE character to
    // request the next page.

    const ssh = try chilkat.Ssh.init();
    defer ssh.deinit();

    const port = 22;
    ssh.connect("172.16.16.100", port) catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        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.
    const password = "mySshPassword";

    ssh.authenticatePw("mySshLogin", password) catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    };

    const channel_num = ssh.quickShell();
    if (channel_num < 0) {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        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.setReadTimeoutMs(15000);

    const case_sensitive = true;

    // In unprivileged mode the switch prompt ends with ">".
    ssh.channelReceiveUntilMatch(channel_num, ">", "utf-8", case_sensitive) catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    };

    var received: [:0]const u8 = ssh.getReceivedText(alloc, channel_num, "utf-8") catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("{s}\n", .{received});

    // Send "ena" to enter privileged mode.  Cisco devices expect a bare CR to terminate a command.
    ssh.channelSendString(channel_num, "ena\r", "utf-8") catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    };

    ssh.channelReceiveUntilMatch(channel_num, "Password:", "utf-8", case_sensitive) catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    };

    received = ssh.getReceivedText(alloc, channel_num, "utf-8") catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("{s}\n", .{received});

    // The enable password is separate from the login password, and likewise should come from a
    // secure source rather than being hard-coded.
    const enable_password = "myEnablePassword";
    ssh.channelSendString(channel_num, enable_password, "utf-8") catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    };

    ssh.channelSendString(channel_num, "\r", "utf-8") catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    };

    // In privileged mode the prompt ends with "#" instead of ">".
    ssh.channelReceiveUntilMatch(channel_num, "#", "utf-8", case_sensitive) catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    };

    received = ssh.getReceivedText(alloc, channel_num, "utf-8") catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("{s}\n", .{received});

    // Run a command whose output is delivered a page at a time.
    ssh.channelSendString(channel_num, "show running-config\r", "utf-8") catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    };

    // Each read ends either at the device prompt (output complete) or at "--More--" (another page
    // is waiting).  Match the full prompt rather than a bare "#", because "#" also appears inside
    // configuration text and would match too early.
    const sa_match = try chilkat.StringArray.init();
    defer sa_match.deinit();
    sa_match.append("MySwitchName#") catch {};
    sa_match.append("--More--") catch {};

    const sb_received = try chilkat.StringBuilder.init();
    defer sb_received.deinit();
    var more_coming: bool = true;

    while (more_coming) {
        ssh.channelReceiveUntilMatchN(channel_num, sa_match, "utf-8", case_sensitive) catch {
            std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
            return;
        };

        sb_received.clear();
        const page_text = ssh.getReceivedText(alloc, channel_num, "utf-8") catch {
            std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
            return;
        };

        sb_received.append(page_text) catch {};
        std.debug.print("{s}\n", .{page_text});

        // If this page ended with "--More--", send a SPACE to request the next page.
        more_coming = sb_received.contains("--More--", case_sensitive);
        if (more_coming) {
            ssh.channelSendString(channel_num, " ", "utf-8") catch {
                std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
                return;
            };
        }
    }

    ssh.disconnect();
}