On Thu, Nov 20, 2014 at 7:35 AM, Eduardo A. Bustamante López <
dual...@gmail.com> wrote:
> Last try:
>
> is_defined4() {
> declare -p -- "$1" 2>/dev/null >&2
> }
>
>
I think using "${#x[@]}" is still the better solution. You probably just
missed [@] in ${#a}? And I actually have declare -p in a code I created
but currently don't use. I now consider this other solution better thanks
to this discussion.
#!/bin/bash
if [[ BASH_VERSINFO -lt 3 ]]; then
echo "Function needs Bash 3.0 or newer."
exit 1
elif [[ BASH_VERSINFO -gt 4 || (BASH_VERSINFO -eq 4 && BASH_VERSINFO[1] -ge
3) ]]; then
function is_defined {
local -n __r=$1
[[ ${#__r[@]} -gt 0 ]]
}
else
function is_defined {
local __r=$1[@]:0:1 __t
__t=("${!__r}")
[[ ${#__t[@]} -gt 0 ]]
}
fi
declare -A a=(['x']=. ['y']=.); unset 'a[x]'
is_defined a && echo "a is defined." || echo "a is not defined."
x=
is_defined x && echo "x is defined." || echo "x is not defined."
y=(1 2 3 4)
is_defined y && echo "y is defined." || echo "y is not defined."
function z { :; }
is_defined z && echo "z is defined." || echo "z is not defined."
Test:
# for A in 3.0 3.1.1 3.2 4.0 4.1 4.2 4.3 current; do echo "---- $A ----";
bash-"$A" temp.sh; done
---- 3.0 ----
temp.sh: line 16: declare: -A: invalid option
declare: usage: declare [-afFirtx] [-p] [name[=value] ...]
a is not defined.
x is defined.
y is defined.
z is not defined.
---- 3.1.1 ----
temp.sh: line 16: declare: -A: invalid option
declare: usage: declare [-afFirtx] [-p] [name[=value] ...]
a is not defined.
x is defined.
y is defined.
z is not defined.
---- 3.2 ----
temp.sh: line 16: declare: -A: invalid option
declare: usage: declare [-afFirtx] [-p] [name[=value] ...]
a is not defined.
x is defined.
y is defined.
z is not defined.
---- 4.0 ----
a is defined.
x is defined.
y is defined.
z is not defined.
---- 4.1 ----
a is defined.
x is defined.
y is defined.
z is not defined.
---- 4.2 ----
a is defined.
x is defined.
y is defined.
z is not defined.
---- 4.3 ----
a is defined.
x is defined.
y is defined.
z is not defined.
---- current ----
a is defined.
x is defined.
y is defined.
z is not defined.
Reference expansion in Bash 2.05b.0 seems broken so I added the version
check for it but it's just optional if you'd never run the code in
2.05b. I dislike the idea of adding the test inside the function itself
but you can also do that. Adding another version of is_defined for 2.05b
may also be good and doable but I no longer find that practical.
The Bash 4.3 version is also just optional.
And of course if you're conservative you can always add a code that
checks if the argument is a valid Bash variable like testing it against
ext. pattern [[:alpha:]_]*([[:alnum:]_]) or regex [[:alpha:]_][[:alnum:]_]*.
It's just up to you if you want to return false (1) if it's invalid or just
send a message and exit the shell.
I used lowercase variable names for everyone's preference.
Cheers,
konsolebox
