Print

This page explains the printing helpers provided by rix/debug.

The examples use the public Rix facade:

cpp

#include <rix.hpp>

and access Debug through:

cpp

rix.debug

Printing is useful for examples, quick checks, local diagnostics, small command-line tools, and development-time output.

For production application logs, prefer the Vix logging system.

Basic example

Create a file:

bash

mkdir -p ~/rix-debug-print
cd ~/rix-debug-print
touch print.cpp

Add:

cpp

#include <rix.hpp>

int main()
{
  rix.debug.print("Hello", "Rix");
  rix.debug.print("rows:", 3);
  rix.debug.print("ready:", true);

  rix.debug.eprint("stderr:", "example error output");

  rix.debug.dprint("debug:", "only useful while developing");

  return 0;
}

Run it:

bash

vix run print.cpp

If Rix is not available yet for single-file usage:

bash

vix install -g rix/rix
vix run print.cpp

Expected output

Standard output should look like this:

txt

Hello Rix
rows: 3
ready: true

The eprint output is written to stderr.

The exact behavior of dprint depends on debug configuration and build mode.

`rix.debug.print`

Use print for normal development output:

cpp

rix.debug.print("Hello", "Rix");

print writes values separated by spaces and adds a trailing newline.

Example:

cpp

rix.debug.print("package:", "rix/debug");
rix.debug.print("version:", rix.debug.version());
rix.debug.print("count:", 3);

This is the most common print helper.

Print multiple values

You can pass several values:

cpp

rix.debug.print("name:", "Ada", "language:", "C++");

Output:

txt

name: Ada language: C++

Each value is rendered and separated by a space.

Print strings

cpp

rix.debug.print("Hello from rix/debug");

Output:

txt

Hello from rix/debug

Print numbers

cpp

rix.debug.print("rows:", 3);
rix.debug.print("port:", 8080);

Output:

txt

rows: 3
port: 8080

Print booleans

cpp

rix.debug.print("ready:", true);
rix.debug.print("failed:", false);

Output shape:

txt

ready: true
failed: false

Print mixed values

cpp

const std::string package = "rix/debug";

rix.debug.print("package:", package, "enabled:", true);

Output:

txt

package: rix/debug enabled: true

`rix.debug.eprint`

Use eprint for error-style output:

cpp

rix.debug.eprint("error:", "something failed");

eprint writes to stderr.

This is useful for examples where an operation can fail:

cpp

auto auth = rix.auth.memory();

auto login = auth.login({
    "ada@example.com",
    "wrong-password"});

if (login.failed())
{
  const auto &error = login.error();

  rix.debug.eprint(
      "auth error:",
      rix.auth.error.to_string(error),
      error.message());

  return 1;
}

Use eprint for local diagnostics, not for production logging.

`rix.debug.dprint`

Use dprint for debug-only output:

cpp

rix.debug.dprint("debug value:", 42);

Use it when the message is only useful while developing.

Example:

cpp

const auto table = rix.csv.parse(
    "name,language\n"
    "Ada,C++\n");

rix.debug.dprint("parsed rows:", table.size());

`rix.debug.sprint`

Use sprint when you want the same rendering as print, but returned as a string.

cpp

const auto line = rix.debug.sprint("rows:", 3);

rix.debug.print(line);

Output:

txt

rows: 3

This is useful when you want to build a message before printing it, storing it, or passing it to another API.

`print` vs `format`

Use print when you want values separated by spaces:

cpp

rix.debug.print("rows:", 3);

Use format when you want placeholder-based text:

cpp

const auto message =
    rix.debug.format("rows: {}", 3);

rix.debug.print(message);

Both are useful.

print is faster to write.

format gives you more control over the message shape.

Complete print example

cpp

#include <rix.hpp>

#include <string>

int main()
{
  const std::string package = "rix/debug";

  rix.debug.print("== print example ==");
  rix.debug.print("package:", package);
  rix.debug.print("ready:", true);
  rix.debug.print("items:", 4);

  const auto line =
      rix.debug.sprint("generated:", package);

  rix.debug.print(line);

  rix.debug.eprint("stderr example:", "local diagnostic");

  return 0;
}

Run it:

bash

vix run print.cpp

Expected standard output:

txt

== print example ==
package: rix/debug
ready: true
items: 4
generated: rix/debug

Print CSV rows

rix.debug.print is useful when working with rix/csv.

cpp

#include <rix.hpp>

int main()
{
  const auto table = rix.csv.parse(
      "name,language\n"
      "Ada,C++\n"
      "Gaspard,Vix\n");

  rix.debug.print("rows:", table.size());

  for (const auto &row : table)
  {
    rix.debug.print("fields:", row.size());
  }

  return 0;
}

Run:

bash

vix run print.cpp

Print Auth errors

eprint is useful for Auth examples.

cpp

#include <rix.hpp>

int main()
{
  auto auth = rix.auth.memory();

  auto login = auth.login({
      "ada@example.com",
      "wrong-password"});

  if (login.failed())
  {
    const auto &error = login.error();

    rix.debug.eprint(
        "auth error:",
        rix.auth.error.to_string(error),
        error.message());

    return 1;
  }

  return 0;
}

Do not print authentication secrets in production.

Avoid printing:

txt

plain-text passwords
password hashes
session ids
raw token values

Print PDF results

eprint is useful when a PDF operation fails.

cpp

#include <rix.hpp>

int main()
{
  auto doc = rix.pdf.document();

  auto &page = doc.add_page();

  page.text(
      page.x_left(),
      page.y_top(),
      "Hello from rix.pdf");

  auto saved = rix.pdf.save(doc, "");

  if (saved.failed())
  {
    rix.debug.eprint(
        "pdf error:",
        rix.pdf.error.to_string(saved.error()),
        saved.error().message());

    return 1;
  }

  rix.debug.print("created:", "example.pdf");

  return 0;
}

Use in a Vix project

Create a Vix application:

bash

vix new debug-print --app
cd debug-print

Add Rix:

bash

vix add rix/rix
vix install

In vix.app, make sure Rix is listed under deps:

txt

deps = [
  "rix/rix",
]

A small vix.app can look like this:

txt

name = "debug-print"
type = "executable"
standard = "c++20"
output_dir = "bin"

sources = [
  "src/main.cpp",
]

include_dirs = [
  "include",
  "src",
]

deps = [
  "rix/rix",
]

packages = [
  "vix",
]

links = [
  "vix::vix",
]

Then use Debug in src/main.cpp:

cpp

#include <rix.hpp>

int main()
{
  rix.debug.print("Hello", "Rix");
  rix.debug.eprint("stderr:", "example");

  return 0;
}

Build and run:

bash

vix build
vix run

Single-file usage

For small scripts, examples, and experiments:

bash

vix run print.cpp

If Rix is installed globally for single-file usage:

bash

vix install -g rix/rix
vix run print.cpp

For project usage, prefer:

bash

vix add rix/rix
vix install

and keep the dependency in vix.app:

txt

deps = [
  "rix/rix",
]

Use only Debug with the facade

If you want the rix.* facade style but only want Debug mounted, define the feature macro before including rix.hpp:

cpp

#define RIX_ENABLE_DEBUG
#include <rix.hpp>

int main()
{
  rix.debug.print("Hello", "Rix");
  return 0;
}

When at least one RIX_ENABLE_* macro is defined, only selected modules are mounted.

Use the independent package

For independent usage, install:

bash

vix add rix/debug
vix install

In vix.app:

txt

deps = [
  "rix/debug",
]

Then include the independent package header:

cpp

#include <rix/debug.hpp>

Use this style when a project only needs Debug and does not need the full unified Rix facade.

For most application documentation, prefer:

cpp

#include <rix.hpp>

Logging note

Printing is not the same as production logging.

Use rix.debug.print, rix.debug.eprint, rix.debug.dprint, and rix.debug.sprint for:

txt

examples
local diagnostics
small tools
tests
quick checks
documentation snippets

For real application logs, prefer the Vix logging system.

Use this rule:

txt

rix.debug -> simple development output
Vix logging -> production logs and runtime observability

Common mistakes

Using print as production logging

rix.debug.print is for development output and examples.

For services and deployed applications, use the Vix logging system.

Printing secrets

Do not print:

txt

plain-text passwords
password hashes
session ids
raw token values

This matters especially when using rix/auth.

Expecting `print` to format placeholders

print does not replace {} placeholders.

Wrong:

cpp

rix.debug.print("Package: {}", "rix/debug");

This prints the values separated by spaces.

Use format when you want placeholder replacement:

cpp

rix.debug.print(
    rix.debug.format("Package: {}", "rix/debug"));

Forgetting `deps`

For a Vix project, do not put Rix packages in packages.

Use:

txt

deps = [
  "rix/rix",
]

packages is for CMake package discovery.

deps is for Vix Registry packages.

What you should remember

Print values:

cpp

rix.debug.print("Hello", "Rix");

Print to stderr:

cpp

rix.debug.eprint("error:", "message");

Debug-only print:

cpp

rix.debug.dprint("debug:", 42);

Build printed output as a string:

cpp

auto line = rix.debug.sprint("rows:", 3);

Use format when you need placeholders:

cpp

auto message = rix.debug.format("Package: {}", "rix/debug");

For a Vix project, install Rix:

bash

vix add rix/rix
vix install

and use:

txt

deps = [
  "rix/rix",
]

Prefer Vix logging for real application logs.

Next step

Learn formatting.

Next: Formatting

Print ​

Basic example ​

Expected output ​

rix.debug.print ​

Print multiple values ​

Print strings ​

Print numbers ​

Print booleans ​

Print mixed values ​

rix.debug.eprint ​

rix.debug.dprint ​

rix.debug.sprint ​

print vs format ​

Complete print example ​

Print CSV rows ​

Print Auth errors ​

Print PDF results ​

Use in a Vix project ​

Single-file usage ​

Use only Debug with the facade ​

Use the independent package ​

Logging note ​

Common mistakes ​

Using print as production logging ​

Printing secrets ​

Expecting print to format placeholders ​

Forgetting deps ​

What you should remember ​

Next step ​

Print

Basic example

Expected output

`rix.debug.print`

Print multiple values

Print strings

Print numbers

Print booleans

Print mixed values

`rix.debug.eprint`

`rix.debug.dprint`

`rix.debug.sprint`

`print` vs `format`

Complete print example

Print CSV rows

Print Auth errors

Print PDF results

Use in a Vix project

Single-file usage

Use only Debug with the facade

Use the independent package

Logging note

Common mistakes

Using print as production logging

Printing secrets

Expecting `print` to format placeholders

Forgetting `deps`

What you should remember

Next step