: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.