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printf

Included in skill bundleshared-skillsView on GitHub ↗

Files

SKILL.mdagentsreferences

Install

Install only this skill with npx skills
npx skills add alisonaquinas/llm-shared-skills --skill 'printf' -g -y
Install the containing skill bundle
/plugin install shared-skills@llm-skills
Download printf-skill.zip
This skill is bundled inside shared-skills. Use npx skills when you only want this skill, or install the bundle once to make every included skill available through the plugin marketplace flow. Browse the full skill bundle repository at github.com/alisonaquinas/llm-shared-skills.

Invoke

Invoke this skill after installation
/shared-skills:printf

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
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