Live manual Debian Live

# Debian Live Manual

# コーディングスタイル

717

# 15. コーディングスタイル

718

この章では Live システムで利用されているコーディングスタイルについて述べます。

719

15.1 互換性

720

- Avoid "bashisms", the codebase must be POSIX compliant and thus universally compatible.

721

- Furthermore it must comply with the version of the POSIX specification chosen by the current Debian Policy.

722

- 'sh -n' と 'checkbashisms' によりスクリプトをチェックできます。

723

- シェルコードが全て確実に 'set -e' で動作するようにしてください。

724

15.2 インデント

725

- 常にスペースよりもタブを使います。

726

- Keep case branch terminators (";;") aligned with the "content" of the branch, rather than the branch "entry".

727

良い例:

728

case "${1}" in
foo)
foobar
;;
bar)
foobar
;;
esac

729

15.3 改行

730

- Generally, lines should be 80 chars at maximum.

731

- Placement of keywords like `then` and `do` should be chosen with good judgement with respect to clutter and readability. For small bits of code in particular it should be preferred to have them on the same line as the prior keyword they relate to (`if`; `for`; etc). Only place on the next line where it makes good sense to do so; typically this might only be to comply with maximum line length restrictions. One situation where they should always be placed on the next line is where what they follow is broken up onto multiple lines, and thus it being on a new line creates clear separation between that and the body of code following it. I.e. :

732

Preferred:

733

if foo; then
bar
fi
for FOO in $ITEMS; do
bar
done
if [ "${MY_LOCATION_VARIABLE}" = "something" ] && [ -e "${MY_OUTPUT_FILE}" ]
then
MY_OTHER_VARIABLE="$(some_bin ${FOOBAR} | awk -F_ '{ print $1 }')"
fi
if [ "${MY_FOO}" = "something" ] && [ -e "path/${FILE_1}" ] ||
[ "${MY_BAR}" = "something_else" ] && [ ${ALLOW} = "true" ]
then
foobar
fi

734

Less ideal:

735

if [ "${MY_LOCATION_VARIABLE}" = "something" ] && [ -e "${MY_OUTPUT_FILE}" ]; then
MY_OTHER_VARIABLE="$(some_bin ${FOOBAR} | awk -F_ '{ print $1 }')"
fi

736

Horrible:

737

if [ "${MY_LOCATION_VARIABLE}" = "something" ] && [ -e "${MY_OUTPUT_FILE}" ] || [ "${MY_LOCATION_VARIABLE}" = "something-else" ] && [ -e "${MY_OUTPUT_FILE_2}" ]; then
MY_OTHER_VARIABLE="$(some_bin ${FOOBAR} | awk -F_ '{ print $1 }')"
fi

738

- Prefer placing the opening brace of a function on a new line (for consistency with established style), and keep the braces aligned with the function name:

739

良い例:

740

Foo ()
{
bar
}

741

Bad (inconsistent with existing style):

742

Foo () {
bar
}

743

Awful:

744

Foo ()
{
bar
}

745

15.4 変数

746

- 変数は常に大文字です。

747

- Config variables used in live-build should start with an `LB_` prefix.

748

- Local function variables should be restricted to local scope.

749

- live-config 中のブートパラメータにつながる変数は `LIVE_` で始めます。

750

- live-config 中の他の変数は全て `_` で始めます。

751

- 変数は大括弧「{}」で囲みます。例えば `$FOO` ではなく `${FOO}` とします。

752

- Always protect variables with quotes to respect potential whitespaces (except where necessary to achieve correct word splitting): write `"${FOO}"` not `${FOO}`.

753

- 一貫性を保つため、変数に値を割り当てるときは常に引用符を使います:

754

悪い例:

755

FOO=bar

756

良い例:

757

FOO="bar"

758

- If multiple variables are used, prefer quoting the full expression:

759

Typically bad:

760

if [ -f "${FOO}"/foo/"${BAR}"/bar ]; then
foobar
fi

761

良い例:

762

if [ -f "${FOO}/foo/${BAR}/bar" ]; then
foobar
fi

763

15.5 その他

764

- Prefer "`|`" (without the surround quotes) as a separator in calls to sed, e.g. "`sed -e 's|foo|bar|'`" (without "").

765

- Don't use the `test` command for comparisons or tests, use "`[`" and "`]`" (without ""); e.g. "`if [ -x /bin/foo ]; ...`" and not "`if test -x /bin/foo; ...`".

766

- Use `case` wherever it makes code more readable than conditional checks (`if foo; ...` and tests without the actual `if` keyword, e.g. `[ -e "${FILE}" ] || exit 0`).

767

- Use "Foo_bar" style names for functions, i.e. a capital first letter, then all lowercase, with sensible use of underscores for better readability.