printf

Overview

printf formats and prints arguments using a format string, like C’s printf. Prefer it over echo when you need reliable escapes, fixed columns, no unexpected options parsing, or portable scripts. Available as a bash builtin and /usr/bin/printf (usually identical enough for ops use).

Keep complex format logic in Scripting → Bash in this book; here are the operator essentials.

Syntax

printf FORMAT [ARGUMENT...]

Common Format Pieces

Sequence	Meaning
%s	String
%d / %i	Decimal integer
%x / %X	Hex integer
%f	Floating point
%b	String with backslash escapes interpreted
%%	Literal %
\n \t \\	Newline, tab, backslash (in FORMAT)

Width/precision: %-20s, %08d, %.2f.

Examples with Explanations

Safe newline print

printf '%s\n' "$var"
printf '%s\n' '---' line1 line2

Repeats the format as needed for leftover arguments (POSIX).

No trailing newline

printf 'Status: %s' ok

Columns

printf '%-12s %8s\n' NAME SIZE
printf '%-12s %8s\n' root 120G
printf '%-12s %8s\n' home 800G

Handy for quick operator tables in scripts.

Zero-pad numbers

printf 'ticket-%04d\n' 7
# ticket-0007

Interpret escapes in data

printf '%b\n' 'line1\nline2'

%b vs putting \n only in FORMAT — know which side holds the escapes.

Hex / bytes (light)

printf '%02x\n' 255
printf '\\x%x' 42; echo

For full hex dumps use xxd.

Build a file

printf 'user=%s\nrole=%s\n' "$USER" admin > /tmp/who.ini

Arbitrary strings that look like options

printf '%s\n' -n
# correctly prints -n  (echo -n would swallow it as a flag)

Notes

• Exit status is non-zero on write errors; format errors are shell-dependent.
• Floating formats and locales: decimal comma/point can surprise — set LC_ALL=C for machine output.
• Prefer printf '%s\n' "$x" over echo "$x" in production shell snippets.
• Builtin printf vs /usr/bin/printf: rare differences; stick to common formats.

Related Commands

• echo — simple print
• sprintf — not a shell command; use command substitution with printf
• column — align tables from text
• xxd — binary/hex dumps

Additional Resources

• help printf (bash)
• man 1 printf