Tool · POSIX shells

shell quote

Paste any string. See it quoted four ways for bash, sh, dash, zsh: single-quoted, double-quoted, ANSI-C, and printf %q. The forms differ in what they preserve and what they let the shell still interpret.

Input string

Quoted forms

Each form is safe to drop into a script. Pick by what you need preserved.

single-quoted (POSIX, all-literal)

enter a string above

Most defensive. Every byte is literal except the closing quote, which is rewritten as '\''. Works in sh, bash, dash, ksh, zsh.

double-quoted (variable expansion live)

enter a string above

Escapes $ ` \ " only. Other characters pass through. Use when you want $variable or $(cmd) to expand at runtime.

ANSI-C ($'...')

enter a string above

For control characters and binary bytes. Newlines become \n, tabs \t, NULs \0. Supported in bash, zsh, ksh93. Not POSIX-portable; dash rejects it.

printf %q (bash's own escaper)

enter a string above

Round-trip safe inside bash: feed this back into bash and you recover the original bytes. Not POSIX-portable. Bash's exact output here varies by version; this implementation picks a safe form rather than mirroring a specific bash release.

Which form, when

Form	Preserves	Lets the shell interpret	Portable
`'…'`	Every byte literally	Nothing	POSIX
`"…"`	Most bytes literally	`$var`, `$(cmd)`, `cmd`, escapes for `$` ` `\` `"`	POSIX
`$'…'`	Bytes via escape codes (`\n`, `\xNN`)	Only the backslash escape codes	bash, zsh, ksh93 only
`printf %q`	Smallest re-parsable form	Nothing (the output is literal-safe)	bash, zsh only

The single-quote trick

You cannot put a single quote inside single quotes. The POSIX idiom is to close the quote, write the literal quote backslash-escaped, then reopen:

it's becomes 'it'\''s'. Four pieces concatenated by adjacency: 'it' then \' then 's'. Works in every POSIX shell.

Common gotchas

Double quotes do not protect $var. If you want the dollar sign literal, single-quote it or backslash-escape \$.
Single quotes do not protect against shell history. In interactive bash, ! may still expand. Disable with set +H or escape as \!.
ANSI-C is not POSIX. Scripts with #!/bin/sh on Debian and Ubuntu run dash. $'\n' fails there. Use printf '%b' '\n' or a literal newline inside single quotes instead.
NUL bytes break shell strings entirely. The shell terminates the string at the first NUL. Use xxd, od, or process substitution if you need to carry binary.
printf %q output uses ANSI-C. The result is not POSIX-portable, only round-trip safe in bash.

References

By Truffle. Source at github.com/truffle-dev/tool-shell-quote. MIT. Sibling tools at /public/tools/.