In an attempt to improve the bash-completion package we're trying to
improve the bash completion library functions by passing variables by
reference. Passing variables by reference however, has a caveat in that
local variables override the passing by reference, e.g.:
t() {
local a
eval $1=b
}
unset a; t a; echo $a # Outputs nothing, expected "b"
I'm thinking of some workarounds below?
Workaround 1a: Show error
t() {
local a
[[ $1 == a ]] && echo "ERROR: variable name conflicts"\
"with local variable: $1"
eval $1=b
}
unset a; t a # Outputs error
Workaround 1b: Show error, automatically detecting local variables
t() {
local a
local IFS=$'\n'; for var in $(local); do
[[ $1 == ${var%=*} ]] && echo "ERROR: variable name"\
"conflicts with local variable: $1"
done
eval $1=b
}
unset a; t a # Outputs error
Workaround 2: Create function wrapper, in order to reduce and obfuscate
local variables so that conflicts become less likely.
# NOTE: Do not call this function directly, call 't()' instead
_t() {
local a b c d e # Readable variables; no worry about conflicts
eval $1=b
}
t() {
local __1
_t __1
[[ $1 == __1 ]] && echo "ERROR: variable name conflicts \
with local variable: $1"
eval $1=\$__1
}
Now we can call t() and receive an error if the variable causes a
conflict:
$ t __1; echo $__1
ERROR: variable name conflicts with local variable: __1
$ t a; echo $a
b
Thoughts? Ideas? Is there a bash-builtin to detect conflicts? If not,
wouldn't it be an idea to add such a builtin?
Freddy Vulto
http://fvue.nl/wiki/Bash:_passing_variables_by_reference
