bash_style.txt

2010-07-22 Jeff McCune <jeff@puppetlabs.com>

Bash style suggestions:

= Cleanup actions =
May be done with trap {} EXIT
# JJM Note the use of a string literal.
# The variable will be dereferenced when the trap fires.
# "Idiom - If $master_pid length is nonzero, then kill $master_pid"
trap '{ test -n "${master_pid:-}" && kill "${master_pid}" ; }' EXIT

= Functions =
Functions should be declared like so:
somefunction() {
  local myvar=${1:-mydefault}
}

= Shell Substitution and Variables =
* Please don't use let or declare to set variables.
* Local variables should be lower case.
* Global variables should be upper case.
* Use of global variables in functions should be avoided.
* :- and := operators may be used to return or set defaults.
  e.g. echo ${FOO:=default} and echo ${FOO:-default}
* Basic string slicing may be done with ## and %%:
  foo=hello/world; echo "${foo%%/*} ${foo##*/}" prints
  "hello world"
* basename "$0" will return the script without path
  The idiom is PROGNAME=$(basename "$0")
* $() should be preferred to `` for readability
* <<'EOF' for a literal here document, <<EOF for an interpolated one

= General Patterns =
Acceptance tests should exit $EXIT_FAILURE or $EXIT_OK if the reach
a valid conclusion about the state of puppet.  All other exit codes
should be considered as an error in the spec test itself.

It's a good idea to run with set -u to catch undefined variables being
used.  Where possible, set -e is also a good idea.

= Bash Pitfalls =
http://mywiki.wooledge.org/BashPitfalls