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:B~ Coding Style
1~coding-style Coding Style
This chapter documents the coding style used in live systems.
2~ 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 $(foo) over `foo`.
_* You can check your scripts with 'sh -n' and 'checkbashisms'.
_* Make sure all shell code runs with 'set -e'.
2~ Indenting
_* Always use tabs over spaces.
2~ Wrapping
_* Generally, lines are 80 chars at maximum.
_* Use the "Linux style" of line breaks:
Bad:
code{
if foo; then
bar
fi
}code
Good:
code{
if foo
then
bar
fi
}code
_* The same holds for functions:
Bad:
code{
Foo () {
bar
}
}code
Good:
code{
Foo ()
{
bar
}
}code
2~ Variables
_* Variables are always in capital letters.
_* Variables used in live-build always start with #{LB_}# prefix.
_* Internal temporary variables in live-build should start with the
#{\_LB_}# prefix.
_* Local variables start with live-build #{\_\_LB_}# prefix.
_* Variables in connection to a boot parameter in live-config start with
#{LIVE_}#.
_* All other variables in live-config start with #{_}# prefix.
_* Use braces around variables; e.g. write #{${FOO}}# instead of #{$FOO}#.
_* Always protect variables with quotes to respect potential whitespaces:
write #{"${FOO}"}# not #{${FOO}}#.
_* For consistency reasons, always use quotes when assigning values to
variables:
Bad:
code{
FOO=bar
}code
Good:
code{
FOO="bar"
}code
_* If multiple variables are used, quote the full expression:
Bad:
code{
if [ -f "${FOO}"/foo/"${BAR}"/bar ]
then
foobar
fi
}code
Good:
code{
if [ -f "${FOO}/foo/${BAR}/bar" ]
then
foobar
fi
}code
2~ Miscellaneous
_* Use "#{|}#" (without the surround quotes) as a separator 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.
_* Use capitalized names for functions to limit messing with the users
environment.
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