Differences between Brash and the Bourne and GNU Bash Shells

Version 1.1.27 lacks or limits the following bash features:

brash command line options are unique to it, and only barely reflect those of bourne or GNU bash. Use brash -h for more details.
array variables are not included in release 1.*.* of brash.
the tilde character, "~", when used as the leading part of a filename, works -- but only for the current user. The ~username/ syntax is not supported.
the keyboard handling lacks the depth of bash's configurability, but is fairly full featured. See "Console Window Edit Keys", below.
the set command is very limited. Use the command "builtins" to get a list of what is supported.
if and while statements only allow 1 command in the conditional clause, but that command can be ( ... ) or { ... } so multiple commands are possible, its just that they must be surrounded by braces or parens.
shopt
bg not available ( but the & operator works to execute commands in the background the jobs command lists background jobs )
caller
enable
env only lets you list the environment, not manipulate it
exec
help
history (instead use fc -l range...)
jobs command is very limited -- it only lists running background jobs
local
mapfile ( but read -f can simulate )
printf
readarray is completely missing, but read -f approximates it (poorly)
readonly
suspend
test ( though [ expression ] does work )
times
trap
typeset
umask
ulimit
wait

Here are some other diferences

Brash has different builtin functions. Use the command builtins to get a list.
Brash reads ~/.brashrc not ~/.bashrc. ~ will be the same as $HOME which will be the same as $USERPROFILE.
The final stage of a pipe command is executed in the current shell environment, not in a sub-shell. Usually this will only be beneficial, but if the final stage polutes your environment, you will have to remember to put the commands in parenthesis.
Brash pre-defines the following variables: