Comprehensive R package for command-line interface styling, semantic messaging, and user communication. Use this skill when working with R code that needs to: (1) Format console output with inline markup and colors, (2) Display errors, warnings, or messages with cli_abort/cli_warn/cli_inform, (3) Show progress indicators for long-running operations, (4) Create semantic CLI elements (headers, lists, alerts, code blocks), (5) Apply themes and customize output styling, (6) Handle pluralization in user-facing text, (7) Work with ANSI strings, hyperlinks, or custom containers. Also use when migrating from base R message/warning/stop, debugging cli code, or improving existing cli usage.
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skills listSkill Instructions
name: r-lib/cli description: > Comprehensive R package for command-line interface styling, semantic messaging, and user communication. Use this skill when working with R code that needs to: (1) Format console output with inline markup and colors, (2) Display errors, warnings, or messages with cli_abort/cli_warn/cli_inform, (3) Show progress indicators for long-running operations, (4) Create semantic CLI elements (headers, lists, alerts, code blocks), (5) Apply themes and customize output styling, (6) Handle pluralization in user-facing text, (7) Work with ANSI strings, hyperlinks, or custom containers. Also use when migrating from base R message/warning/stop, debugging cli code, or improving existing cli usage.
CLI for R Packages
When to Use What
task: Display error with context and formatting
use: cli_abort() with inline markup and bullet lists
task: Show warning with formatting
use: cli_warn() with inline markup
task: Display informative message
use: cli_inform() with inline markup
task: Show progress for counted operations
use: cli_progress_bar() with total count
task: Show simple progress steps
use: cli_progress_step() with status messages
task: Format code or function names
use: {.code ...} or {.fn package::function}
task: Format file paths
use: {.file path/to/file}
task: Format package names
use: {.pkg packagename}
task: Format variable names
use: {.var variable_name}
task: Format values
use: {.val value}
task: Handle singular/plural text
use: {?s} or {?y/ies} with pluralization
task: Create headers
use: cli_h1(), cli_h2(), cli_h3()
task: Create alerts
use: cli_alert_success(), cli_alert_danger(), cli_alert_warning(), cli_alert_info()
task: Create lists
use: cli_ul(), cli_ol(), cli_dl() with cli_li()
Inline Markup Essentials
Use inline markup with {.class content} syntax to format text:
# Basic formatting
cli_text("Function {.fn mean} calculates averages")
cli_text("Install package {.pkg dplyr}")
cli_text("See file {.file ~/.Rprofile}")
cli_text("{.var x} must be numeric, not {.obj_type_of {x}}")
cli_text("Got value {.val {x}}"))
# Code formatting
cli_text("Use {.code sum(x, na.rm = TRUE)}")
# Paths and arguments
cli_text("Reading from {.path /data/file.csv}")
cli_text("Set {.arg na.rm} to TRUE")
# Types and classes
cli_text("Object is {.cls data.frame}")
# Emphasis
cli_text("This is {.emph important}")
cli_text("This is {.strong critical}")
# Fields
cli_text("The {.field name} field is required")
Vector Collapsing
Vectors are automatically collapsed with commas and "and":
pkgs <- c("dplyr", "tidyr", "ggplot2")
cli_text("Installing packages: {.pkg {pkgs}}")
#> Installing packages: dplyr, tidyr, and ggplot2
files <- c("data.csv", "script.R")
cli_text("Found {length(files)} file{?s}: {.file {files}}")
#> Found 2 files: data.csv and script.R
Escaping Braces
Use double braces {{ and }} to escape literal braces:
cli_text("Use {{variable}} syntax in glue")
#> Use {variable} syntax in glue
For complete markup reference: See references/inline-markup.md for all 50+ inline classes, edge cases, nesting rules, and advanced patterns.
Pluralization Basics
Use {?} for pluralization with three patterns:
Single Alternative
nfile <- 1
cli_text("Found {nfile} file{?s}")
#> Found 1 file
nfile <- 3
cli_text("Found {nfile} file{?s}")
#> Found 3 files
Two Alternatives
ndir <- 1
cli_text("Found {ndir} director{?y/ies}")
#> Found 1 directory
ndir <- 5
cli_text("Found {ndir} director{?y/ies}")
#> Found 5 directories
Three Alternatives (zero/one/many)
nfile <- 0
cli_text("Found {nfile} file{?s}: {?no/the/the} file{?s}")
#> Found 0 files: no files
nfile <- 1
cli_text("Found {nfile} file{?s}: {?no/the/the} file{?s}")
#> Found 1 file: the file
nfile <- 3
cli_text("Found {nfile} file{?s}: {?no/the/the} file{?s}")
#> Found 3 files: the files
Helpers: qty() and no()
Use no() to display "no" instead of zero:
nfile <- 0
cli_text("Found {no(nfile)} file{?s}")
#> Found no files
Use qty() to set quantity explicitly:
nupd <- 3
ntotal <- 10
cli_text("{nupd}/{ntotal} {qty(nupd)} file{?s} {?needs/need} updates")
#> 3/10 files need updates
For advanced pluralization: See references/inline-markup.md for edge cases and complex patterns.
CLI Conditions: Core Patterns
Use cli conditions instead of base R for better formatting:
cli_abort() - Formatted Errors
# Before (base R)
stop("File not found: ", path)
# After (cli)
cli_abort("File {.file {path}} not found")
# With bullets for context
check_file <- function(path) {
if (!file.exists(path)) {
cli_abort(c(
"File not found",
"x" = "Cannot read {.file {path}}",
"i" = "Check that the file exists"
))
}
}
cli_warn() - Formatted Warnings
# Before (base R)
warning("Column ", col, " has missing values")
# After (cli)
cli_warn("Column {.field {col}} has missing values")
# With context
cli_warn(c(
"Data quality issues detected",
"!" = "Column {.field {col}} has {n_missing} missing value{?s}",
"i" = "Consider using {.fn tidyr::drop_na}"
))
cli_inform() - Formatted Messages
# Before (base R)
message("Processing ", n, " files")
# After (cli)
cli_inform("Processing {n} file{?s}")
# With structure
cli_inform(c(
"v" = "Successfully loaded {.pkg dplyr}",
"i" = "Version {packageVersion('dplyr')}"
))
Bullet Types
"x"- Error/problem (red X)"!"- Warning (yellow !)"i"- Information (blue i)"v"- Success (green checkmark)"*"- Bullet point">"- Arrow/pointer
For advanced error design: See references/conditions.md for error design principles, rlang integration, testing strategies, and real-world patterns.
Basic Progress Indicators
Simple Progress Steps
process_data <- function() {
cli_progress_step("Loading data")
data <- load_data()
cli_progress_step("Cleaning data")
clean <- clean_data(data)
cli_progress_step("Analyzing data")
analyze(clean)
}
Basic Progress Bar
process_files <- function(files) {
cli_progress_bar("Processing files", total = length(files))
for (file in files) {
process_file(file)
cli_progress_update()
}
}
Auto-Cleanup
Progress bars auto-close when the function exits:
process <- function() {
cli_progress_bar("Working", total = 100)
for (i in 1:100) {
Sys.sleep(0.01)
cli_progress_update()
}
# No need to call cli_progress_done() - auto-closes
}
For advanced progress: See references/progress.md for nested progress, custom formats, parallel processing, all progress variables, and Shiny integration.
Semantic CLI Elements
Headers
cli_h1("Main Section")
cli_h2("Subsection")
cli_h3("Detail")
Alerts
cli_alert_success("Operation completed successfully")
cli_alert_danger("Critical error occurred")
cli_alert_warning("Potential issue detected")
cli_alert_info("Additional information available")
Text and Code
# Regular text with markup
cli_text("This is formatted text with {.emph emphasis}")
# Code blocks
cli_code(c(
"library(dplyr)",
"mtcars %>% filter(mpg > 20)"
))
# Verbatim text (no formatting)
cli_verbatim("This is displayed exactly as-is: {not interpolated}")
Lists
# Unordered list
cli_ul()
cli_li("First item")
cli_li("Second item")
cli_end()
# Ordered list
cli_ol()
cli_li("First step")
cli_li("Second step")
cli_end()
# Definition list
cli_dl()
cli_li(c(name = "The name field"))
cli_li(c(email = "The email address"))
cli_end()
Common Workflows
Base R to CLI Migration
# Before: Base R error handling
validate_input <- function(x, y) {
if (!is.numeric(x)) {
stop("x must be numeric")
}
if (length(y) == 0) {
stop("y cannot be empty")
}
if (length(x) != length(y)) {
stop("x and y must have the same length")
}
}
# After: CLI error handling
validate_input <- function(x, y) {
if (!is.numeric(x)) {
cli_abort(c(
"{.arg x} must be numeric",
"x" = "You supplied a {.cls {class(x)}} vector",
"i" = "Use {.fn as.numeric} to convert"
))
}
if (length(y) == 0) {
cli_abort(c(
"{.arg y} cannot be empty",
"i" = "Provide at least one element"
))
}
if (length(x) != length(y)) {
cli_abort(c(
"{.arg x} and {.arg y} must have the same length",
"x" = "{.arg x} has length {length(x)}",
"x" = "{.arg y} has length {length(y)}"
))
}
}
Error Message with Rich Context
check_required_columns <- function(data, required_cols) {
actual_cols <- names(data)
missing_cols <- setdiff(required_cols, actual_cols)
if (length(missing_cols) > 0) {
cli_abort(c(
"Required column{?s} missing from data",
"x" = "Missing {length(missing_cols)} column{?s}: {.field {missing_cols}}",
"i" = "Data has {length(actual_cols)} column{?s}: {.field {actual_cols}}",
"i" = "Add the missing column{?s} or check for typos"
))
}
invisible(data)
}
Function with Progress Bar
process_files <- function(files, verbose = TRUE) {
n <- length(files)
if (verbose) {
cli_progress_bar(
format = "Processing {cli::pb_bar} {cli::pb_current}/{cli::pb_total} [{cli::pb_eta}]",
total = n
)
}
results <- vector("list", n)
for (i in seq_along(files)) {
results[[i]] <- process_file(files[[i]])
if (verbose) {
cli_progress_update()
}
}
results
}
Resources & Advanced Topics
Reference Files
-
references/inline-markup.md - Complete catalog of inline classes organized by category, advanced patterns, nesting rules, and real-world examples
-
references/conditions.md - Advanced error design patterns, rlang integration, testing with testthat snapshots, migration guide, and anti-patterns
-
references/progress.md - Nested progress bars, custom formats, all progress variables, parallel processing, Shiny integration, and debugging
-
references/themes.md - Complete theming system with CSS-like selectors, container functions, color palettes, custom themes, and accessibility
-
references/ansi-operations.md - ANSI string operations (align, columns, nchar, etc.), hyperlinks, color detection, testing CLI output, and troubleshooting
External Resources
Related Packages
- rlang - Condition handling and error objects integrate with cli
- glue - String interpolation powers cli's
{}syntax - testthat - Snapshot testing for cli output
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