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Debian Live Manual

Project

14. Coding Style

This chapter documents the coding style used in live-boot and others.

14.1 Compatibility

  • Don't use syntax or semantics that are unique to the Bash shell. For example, the use of array constructs.
  • Only use the POSIX subset - for example, use $(foo) over `foo`.
  • You can check your scripts with 'sh -n' and 'checkbashisms'.
  • 14.2 Indenting

  • Always use tabs over spaces.
  • 14.3 Wrapping

  • Generally, lines are 80 chars at maximum.
  • Use the "Linux style" of line breaks:
  • Bad:

    if foo; then
             bar
    fi

    Good:

    if foo
    then
             bar
    fi

  • The same holds for functions:
  • Bad:

    foo () {
             bar
    }

    Good:

    foo ()
    {
             bar
    }

    14.4 Variables

  • Variables are always in capital letters.
  • Variables that used in lb config always start with LB_ prefix.
  • Internal temporary variables in live-build should start with the _LB_ prefix.
  • Local variables start with live-build __LB_ prefix.
  • Variables in connection to a boot parameter in live-config start with LIVE_.
  • All other variables in live-config start with _ prefix.
  • Use braces around variables; e.g. write ${FOO} instead of $FOO.
  • Always protect variables with quotes to respect potential whitespaces: write "${FOO}" not ${FOO}.
  • For consistency reasons, always use quotes when assigning values to variables:
  • Bad:

    FOO=bar

    Good:

    FOO="bar"

  • If multiple variables are used, quote the full expression:
  • Bad:

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

    Good:

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

    14.5 Miscellaneous

  • Use "|" (without the surround quotes) as a seperator in calls to sed, e.g. "sed -e 's|foo|bar|'" (without "").
  • Don't use the test command for comparisons or tests, use "[" "]" (without ""); e.g. "if [ -x /bin/foo ]; ..." and not "if test -x /bin/foo; ...".
  • Use case wherever possible over test, as it's easier to read and faster in execution.

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