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Resolve an Absolute Remote Path with SFTP RealPath

Demonstrates the Chilkat SFtp.RealPath method, which asks the server to canonicalize a path and returns the resulting absolute remote path. The first argument is the original path and the second is an optional compose path (SFTP v5 or later); pass an empty string when no composition is needed.

Background: The server — not the client — owns the remote filesystem's layout, so path canonicalization must happen on the server. RealPath resolves ., .., and symbolic links into a single absolute path, which is the reliable way to learn the session's home directory (canonicalize .) or to turn a relative path into an absolute one before storing or displaying it. On SFTP v5 and later, the compose path can additionally join or override the original.

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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 SFtp.RealPath method, which asks the server to canonicalize a path and
    // returns the resulting absolute remote path.  The 1st argument is the original path and the
    // 2nd is an optional compose path (SFTP v5+), which may be an empty string.

    const sftp = try chilkat.SFtp.init();
    defer sftp.deinit();

    // Step 1: Connect the SSH transport.  Port 22 is the usual port.
    const port = 22;
    sftp.connect("sftp.example.com", port) catch {
        std.debug.print("{s}\n", .{try sftp.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";

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

    // Step 3: Open the SFTP subsystem.  This must be done after authentication and before any
    // file or directory operations.
    sftp.initializeSftp() catch {
        std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
        return;
    };

    // Resolve "." to the absolute path of the session's default (home) directory.  No compose path
    // is needed, so the 2nd argument is an empty string.
    const home_dir = sftp.realPath(alloc, ".", "") catch {
        std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("Home directory: {s}\n", .{home_dir});

    // Canonicalize a relative path with "..", resolving it to an absolute path.
    const resolved = sftp.realPath(alloc, "subdir/../otherdir", "") catch {
        std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("Resolved path: {s}\n", .{resolved});

    sftp.disconnect();
}