shfmt

In this document

• Overview
• Usage
• Installation
• Examples

Overview

The majority of tests (and scripts overall) in the SPDK repo are written in Bash (with a quite significant emphasis on "Bashism"), thus a style formatter, shfmt, was introduced to help keep the .sh code consistent across the entire repo. For more details on the tool itself, please see shfmt.

We also advise to use 4.4 Bash as a minimum version to make sure scripts across the whole repo work as intended.

Usage

On the CI pool, the shfmt is run against all the updated .sh files that have been committed but not merged yet. Additionally, shfmt will pick all .sh present in the staging area when run locally from our pre-commit hook (via check_format.sh). In case any style errors are detected, a patch with needed changes is going to be generated and either build (CI) or the commit will be aborted. Said patch can be then easily applied:

# Run from the root of the SPDK repo
patch --merge -p0 <shfmt-3.1.0.patch

The name of the patch is derived from the version of shfmt that is currently in use (3.1.0 is currently supported).

Please, see ./scripts/check_format.sh for all the arguments the shfmt is run with. Additionally, Examples has more details on how each of the arguments behave.

Installation

The shfmt can be easily installed via pkgdep.sh:

./scripts/pkgdep.sh -d

This will install all the developers tools, including shfmt, on the local system. The precompiled binary will be saved, by default, to /opt/shfmt and then linked under /usr/bin. Both paths can be changed by setting SHFMT_DIR and SHFMT_DIR_OUT in the environment. Example:

SHFMT_DIR=/keep_the_binary_here \
SHFMT_DIR_OUT=/and_link_it_here \
  ./scripts/pkgdep.sh -d

Examples

#######################################
if foo=$(bar); then
  echo "$foo"
fi
 
exec "$foo" \
  --bar \
  --foo
 
# indent_style = tab
 
if foo=$(bar); then
        echo "$foo"
fi
 
exec foobar \
        --bar \
        --foo
######################################
if foo=$(bar); then
        echo "$foo" && \
        echo "$(bar)"
fi
# binary_next_line = true
if foo=$(bar); then
        echo "$foo" \
                && echo "$(bar)"
fi
 
# Note that each break line is also being indented:
 
if [[ -v foo ]] \
&& [[ -v bar ]] \
&& [[ -v foobar ]]; then
        echo "This is foo"
fi
# ->
if [[ -v foo ]] \
        && [[ -v bar ]] \
        && [[ -v foobar ]]; then
        echo "This is foo"
fi
 
# Currently, newlines are being escaped even if syntax-wise
# they are not needed, thus watch for the following:
if [[ -v foo
        && -v bar
        && -v foobar ]]; then
        echo "This is foo"
fi
#->
if [[ -v foo && -v \
        bar && -v \
        foobar ]]; then
        echo "This is foo"
fi
# This, unfortunately, also breaks the -bn behavior.
# (see https://github.com/mvdan/sh/issues/565) for details.
######################################
case "$FOO" in
        BAR)
        echo "$FOO" ;;
esac
# switch_case_indent = true
case "$FOO" in
        BAR)
                echo "$FOO"
                ;;
esac
######################################
exec {foo}>bar
:>foo
exec {bar}<foo
# -sr
exec {foo}> bar
: > foo
exec {bar}< foo
######################################
# miscellaneous, enforced by shfmt
(( no_spacing_at_the_beginning & ~and_no_spacing_at_the_end ))
: $(( no_spacing_at_the_beginning & ~and_no_spacing_at_the_end ))
 
# ->
((no_spacing_at_the_beginning & ~and_no_spacing_at_the_end))
: $((no_spacing_at_the_beginning & ~and_no_spacing_at_the_end))