Coding Style

Coding Style

This chapter documents the coding style used in live systems.

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'.

Indenting

●  Always use tabs over spaces.

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
 }  

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:

 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  

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.