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Release an SSH Channel's Local Resources

Demonstrates the Chilkat Ssh.ChannelRelease method, which releases Chilkat's retained local resources for a channel after all output and exit information has been retrieved. The only argument is the channel number.

Background: Chilkat retains a channel's buffered output and exit information after the channel closes, so you can still read a command's final output. That retention costs memory, and a long-running program that opens many channels should release each one when finished with it. Note this is not a channel-closing method — it sends neither EOF nor CLOSE. Retrieve everything you need first, because releasing discards it.

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

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

    // Demonstrates the Ssh.ChannelRelease method, which releases Chilkat's retained local resources
    // for a channel after all output and exit information has been retrieved.  The only argument is
    // the channel number.

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

    const ssh_port = 22;
    ssh.connect("ssh.example.com", ssh_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;
    };

    // Open a session channel.  A negative return value indicates failure.
    const channel_num = ssh.openSessionChannel();
    if (channel_num < 0) {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    }

    ssh.sendReqExec(channel_num, "uname -a") catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    };

    // 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.
    ssh.setReadTimeoutMs(15000);

    // Retrieve everything of interest before releasing the channel.
    ssh.channelReceiveToClose(channel_num) catch {
        std.debug.print("{s}\n", .{try ssh.getLastErrorText(alloc)});
        return;
    };

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

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

    // Release the retained local resources.  This does not send EOF or CLOSE.
    ssh.channelRelease(channel_num);

    ssh.disconnect();
}