sh
A shell parser, formatter and interpreter. Supports POSIX Shell and
Bash. Requires Go 1.7 or later.
shfmt
go get -u github.com/mvdan/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 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.
Packages are available for Arch, 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 github.com/mvdan/sh/cmd/gosh
Experimental shell executable using interp
. Work in progress and
unstable - the name and package path might change in the future too.
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
- Bash index expressions must be an arithmetic expression or a single
word. If you must use a string with spaces, quote it. This is because
the static parser can't know whether the array is an associative array
(string keys) since that depends on having called or not
declare -A
.
$ echo '${array[spaced string]}' | shfmt
1:16: not a valid arithmetic operator: string
$((
and ((
ambiguity is not suported. Backtracking would greatly
complicate the parser and make stream support - io.Reader
-
impossible. In practice, 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
, let
and eval
are parsed as keywords.
This is to let the static parser parse them completely and build their
AST better than just a slice of arguments.