Alison Aquinas logoAlison's LLM Plugins

printf

Included in pluginshared-skillsView on GitHub ↗

Files

SKILL.mdagentsreferences

Install

Install the containing plugin
/plugin install shared-skills@llm-skills
Invoke this skill after installation
/shared-skills:printf
Download printf-skill.zip
This skill is bundled inside shared-skills. Install the plugin once, then Claude Code can use any of its included skills. Browse the full plugin repository at github.com/alisonaquinas/llm-shared-skills.

SKILL.md

name: printf description: > Format and print text portably with printf for shell scripting, structured output, ANSI colour, and precise escape-sequence control. Use when the agent needs portable output that works across bash, dash, sh, and zsh; when format strings, field widths, numeric formatting, or null-delimited output are required; or when echo's portability limitations make it unsuitable.

printf

Produce formatted output portably across all POSIX shells. Prefer printf over echo in scripts whenever escape sequences, format strings, or cross-shell portability matter.

Quick Start

  1. Basic output: printf '%s\n' "Hello, world"
  2. Formatted: printf '%-20s %d\n' "count:" 42
  3. Write to file: printf '%s\n' "content" > file.txt

Intent Router

  • references/cheatsheet.md — Format specifiers, escape sequences, field widths, common invocations
  • references/advanced-usage.md — Multiline output, ANSI colour, heredoc alternatives, null-delimited pipelines, scripting patterns
  • references/troubleshooting.md — % in variables, portability pitfalls, locale issues, cross-shell differences

Core Workflow

  1. Use '%s\n' as the default format for safe variable output — no escape interpretation, always adds a newline
  2. Prefer printf over echo -e in any script that may run under sh or dash
  3. Use format specifiers (%d, %f, %.2f) for numeric output
  4. Use field widths (%-20s, %10d) for aligned tabular output
  5. Use printf '%s\0' for null-delimited output safe for xargs -0

Quick Command Reference

printf '%s\n' "Hello"               # Safe string output (no escape interp)
printf '%s\n' "$var"                # Variable output — always quoted
printf 'Hello, %s!\n' "$name"       # Interpolate into format string
printf '%d items\n' 42              # Integer
printf '%.2f\n' 3.14159             # Float with 2 decimal places
printf '%05d\n' 7                   # Zero-padded: 00007
printf '%-20s %s\n' "Key:" "Value"  # Left-aligned column
printf '%20s %s\n' "Key:" "Value"   # Right-aligned column
printf '%s\t%s\n' "col1" "col2"     # Tab-separated
printf '\n'                         # Blank line
printf '%s\n' "a" "b" "c"          # Multiple args: one per line
printf '%s\n' "$@"                  # Print all positional parameters
printf '%s\0' file1 file2           # Null-delimited (for xargs -0)
printf '\033[1m%s\033[0m\n' "Bold"  # ANSI bold
printf '\033[32m%s\033[0m\n' "Green" # ANSI green
printf '%s\n' "text" > file.txt     # Write to file
printf '%s\n' "more" >> file.txt    # Append to file
printf '%s\n' "err" >&2             # Write to stderr
man printf                          # Full manual

Format specifiers

SpecifierMeaningExample
%sStringprintf '%s' "$var"
%dDecimal integerprintf '%d' 42
%fFloating pointprintf '%.2f' 3.14
%eScientific notationprintf '%e' 123456
%xHexadecimalprintf '%x' 255 → ff
%oOctalprintf '%o' 8 → 10
%bString with backslash escape processingprintf '%b' 'line1\nline2'
%qShell-quoted stringprintf '%q' "with spaces"
%%Literal %printf '100%%\n'

Safety Notes

AreaGuardrail
Variable as format stringNever pass $var as the format argument: printf "$var". If $var contains %s, %d, etc., printf will interpret them. Always use printf '%s\n' "$var".
File overwriteprintf '...' > file silently overwrites. Use >> to append. Enable set -o noclobber to prevent.
Secrets in outputprintf arguments may appear in process listings. Avoid printing passwords or tokens in environments where ps output is visible.
Locale and numbers%f output is locale-sensitive — decimal separators may be , instead of .. Use LC_NUMERIC=C printf '%.2f' "$n" for consistent dot-decimal output.

Source Policy

  • printf is a POSIX built-in available in bash, dash, sh, zsh, and ksh.
  • Treat help printf (bash) and man 1 printf (external) as runtime truth — they differ slightly.
  • In bash, printf -v varname '%s' "$val" assigns to a variable without a subshell.

See Also

  • $echo for quick interactive output where portability is not a concern
  • $cat for printing file contents rather than formatted strings
  • tee for writing to both stdout and a file simultaneously
← Back to marketplace