sh
A shell parser, formatter and interpreter. Supports POSIX Shell, Bash and
mksh. Requires Go 1.9 or later.
shfmt
go get -u mvdan.cc/sh/cmd/shfmt
shfmt
formats shell programs. It can use tabs or any number of spaces to
indent. See canonical.sh for a quick look at its default
style.
You can feed it standard input, any number of files or any number of directories
to recurse into. When recursing, it will operate on .sh
and .bash
files and
ignore files starting with a period. It will also operate on files with no
extension and a shell shebang.
shfmt -l -w script.sh
Use -i N
to indent with a number of spaces instead of tabs. There are other
formatting options - see shfmt -h
. For example, to get the formatting
appropriate for Google's Style guide, use shfmt -i 2 -ci
.
Packages are available for Arch, CRUX, Homebrew, NixOS and Void.
Advantages over bash -n
bash -n
can be useful to check for syntax errors in shell scripts. However,
shfmt >/dev/null
can do a better job as it checks for invalid UTF-8 and does
all parsing statically, including checking POSIX Shell validity:
$ echo '${foo:1 2}' | bash -n
$ echo '${foo:1 2}' | shfmt
1:9: not a valid arithmetic operator: 2
$ echo 'foo=(1 2)' | bash --posix -n
$ echo 'foo=(1 2)' | shfmt -p
1:5: arrays are a bash feature
gosh
go get -u mvdan.cc/sh/cmd/gosh
Experimental shell that uses interp
. Work in progress, so don't expect
stability just yet.
Fuzzing
This project makes use of go-fuzz to find crashes and hangs in both the parser
and the printer. To get started, run:
git checkout fuzz
./fuzz
Caveats
- When indexing Bash associative arrays, always use quotes. The static parser
will otherwise have to assume that the index is an arithmetic expression.
$ echo '${array[spaced string]}' | shfmt
1:16: not a valid arithmetic operator: string
$ echo '${array[dash-string]}' | shfmt
${array[dash - string]}
$((
and ((
ambiguity is not suported. Backtracking would complicate the
parser and make streaming support via io.Reader
impossible. The POSIX spec
recommends to space the operands if $( (
is meant.
$ echo '$((foo); (bar))' | shfmt
1:1: reached ) without matching $(( with ))
- Some builtins like
export
and let
are parsed as keywords. This is to allow
statically parsing them and building their syntax tree, as opposed to just
keeping the arguments as a slice of arguments.
JavaScript
A subset of the Go packages are available as an npm package called mvdan-sh.
See the _js directory for more information.