shfmt - Man Page

Format shell programs

Examples (TL;DR)

Print a formatted version of a shell script: shfmt path/to/file
List unformatted files: shfmt --list path/to/directory
Write the result to the file instead of printing it to the terminal: shfmt --write path/to/file
Simplify the code, removing redundant pieces of syntax (i.e. removing "$" from vars in expressions): shfmt --simplify path/to/file

shfmt formats shell programs. If the only argument is a dash (-) or no arguments are given, standard input will be used. If a given path is a directory, all shell scripts found under that directory will be used.

If any EditorConfig files are found, they will be used to apply formatting options. If any parser or printer flags are given to the tool, no EditorConfig files will be used. A default like -i=0 can be used for this purpose.

shfmt's default shell formatting was chosen to be consistent, common, and predictable. Some aspects of the format can be configured via printer flags.

Options

Generic flags

-version

Show version and exit.

-l, --list

List files whose formatting differs from shfmt's.

-w, --write

Write result to file instead of stdout.

-d, --diff

Error with a diff when the formatting differs.

The diff uses color when the output is a terminal. To never use color, set a non-empty NO_COLOR or TERM=dumb. To always use color, set a non-empty FORCE_COLOR.

-s, --simplify

Simplify the code.

-mn, --minify

Minify the code to reduce its size (implies -s).

Parser flags

-ln, --language-dialect <str>

Language dialect (bash/posix/mksh/bats, default auto).

When set to auto, the language is detected from the input filename, as long as it has a shell extension like foo.mksh. Otherwise, if the input begins with a shell shebang like #!/bin/sh, that's used instead. If neither come up with a result, bash is used as a fallback.

The filename extension .sh is a special case: it implies posix, but may be overriden by a valid shell shebang.

-p, --posix

Shorthand for -ln=posix.

-filename str

Provide a name for the standard input file.

Printer flags

-i, --indent <uint>: Indent: 0 for tabs (default), >0 for number of spaces.
-bn, --binary-next-line: Binary ops like && and | may start a line.
-ci, --case-indent: Switch cases will be indented.
-sr, --space-redirects: Redirect operators will be followed by a space.
-kp, --keep-padding: Keep column alignment paddings.
-fn, --func-next-line: Function opening braces are placed on a separate line.

Utility flags

-f, --find: Recursively find all shell files and print the paths.
--to-json: Print syntax tree to stdout as a typed JSON.
--from-json: Read syntax tree from stdin as a typed JSON.

Examples

Format all the scripts under the current directory, printing which are modified:

shfmt -l -w .

For CI, one can use a variant where formatting changes are just shown as diffs:

shfmt -d .

The following formatting flags closely resemble Google's shell style defined in <https://google.github.io/styleguide/shellguide.html>:

shfmt -i 2 -ci -bn

Below is a sample EditorConfig file as defined by <https://editorconfig.org/>, showing how to set any option:

  [*.sh]
  # like -i=4
  indent_style = space
  indent_size = 4

shell_variant      = posix # --language-variant
binary_next_line   = true
switch_case_indent = true  # --case-indent
space_redirects    = true
keep_padding       = true
function_next_line = true  # --func-next-line

# Ignore the entire "third_party" directory.
[third_party/**]
ignore = true

shfmt can also replace bash -n to check shell scripts for syntax errors. It is more exhaustive, as it parses all syntax statically and requires valid UTF-8:

  $ echo '${foo:1 2}' | bash -n
  $ echo '${foo:1 2}' | shfmt >/dev/null
  1:9: not a valid arithmetic operator: 2
  $ echo 'foo=(1 2)' | bash --posix -n
  $ echo 'foo=(1 2)' | shfmt -p >/dev/null
  1:5: arrays are a bash feature

Authors

Maintained by Daniel Martí <mvdan@mvdan.cc>, who is assisted by other open source contributors. For more information and development, see <https://github.com/mvdan/sh>.

Info

2024-01-24