On 28/06/2023 00:40, Kerin Millar wrote:
On Tue, 27 Jun 2023 21:52:53 +0200
of1 <of1@disroot.org> wrote:
On 27/06/2023 21:05, Kerin Millar wrote:
It doesn't work at all for >=5.2. The reason for this is interesting and I may
make a separate post about it.
Prior to 5.2, it can easily be tricked into printing names that do not exist.
$ VAR=$'\nNONEXISTENT=' ./declare-P | grep ^NONEXISTENT
NONEXISTENT
Thank you. I was just reading the discussion in Gentoo forum and
realizing that I've been to quickly: it doesn't pass the
FOO=$'\nBAR BAZ QUUX=' test. But what about this? (I also quickly
tested with Bash 5.2.15).
FOO=$'\nBAR BAZ QUUX='
VAR=$'\nNONEXISTENT='
declare-P() {
local curVar
declare -a curVars
readarray -t curVars <<<"$1"
curVars=( "${curVars[@]%%=*}" )
curVars=( "${curVars[@]##* }" )
for curVar in "${curVars[@]}"; do
### we can use [[ -v "$curVar" ]] at some point!
[[ "${curVar//[a-zA-Z0-9_]}" || \
"${curVar:0:1}" == [0-9] || \
! -v "$curVar" || \
! "$curVar" =~ $2 ]] || printf '%s\n' "$curVar"
done
}
declare-P "$(declare -p)"
echo "##################"
declare-P "$(declare -p)" "QU|^NON|VAR"r
This use of test -v is probably sufficient to address that particular issue. It
is just as well that the test occurs after determining that the string is a
valid identifier because test -v has the power to facilitate arbitrary code
execution.
My assertion that your code is broken in 5.2 was incorrect. Rather, the problem
seems to be that regcomp(3) behaviour differs across platforms, where given an
empty expression to compile. To address that, you could determine whether a
second positional parameter was given and is non-empty before proceeding to use
it.
Thank you, good to know. I think that ${2:-.} should be correct.
Curiously, repeated invocation may lead to obvious issues of resource
consumption.
# This is excruciatingly expensive
time for i in {1..100}; do
declare-P "$(declare -p)"
done
# This is not so expensive (!)
time for i in {1..100}; do
declare-P "$(declare -p)"
:
done
I made some testing by adding
echo -n "$(( ++COUNT ))>$(wc -c <<<"$1") "
echo "$1" >"/tmp/declare-P$COUNT"
to the function:
1>4651 2>9785 3>15283 4>21504 5>29173 6>39739 7>56095 8>84036
9>135145 10>232592 11>422710 12>798174 13>1544326 14>3031854
15>6002134 16>11937918 ^C
ls -rtnh /tmp/declare-P*
-rw-r--r-- 1 1000 1000 4,6K 28 juin 11:09 /tmp/declare-P1
-rw-r--r-- 1 1000 1000 9,6K 28 juin 11:09 /tmp/declare-P2
-rw-r--r-- 1 1000 1000 15K 28 juin 11:09 /tmp/declare-P3
-rw-r--r-- 1 1000 1000 21K 28 juin 11:09 /tmp/declare-P4
-rw-r--r-- 1 1000 1000 29K 28 juin 11:09 /tmp/declare-P5
-rw-r--r-- 1 1000 1000 39K 28 juin 11:09 /tmp/declare-P6
-rw-r--r-- 1 1000 1000 55K 28 juin 11:09 /tmp/declare-P7
-rw-r--r-- 1 1000 1000 83K 28 juin 11:09 /tmp/declare-P8
-rw-r--r-- 1 1000 1000 132K 28 juin 11:09 /tmp/declare-P9
-rw-r--r-- 1 1000 1000 228K 28 juin 11:09 /tmp/declare-P10
-rw-r--r-- 1 1000 1000 413K 28 juin 11:09 /tmp/declare-P11
-rw-r--r-- 1 1000 1000 780K 28 juin 11:09 /tmp/declare-P12
-rw-r--r-- 1 1000 1000 1,5M 28 juin 11:09 /tmp/declare-P13
-rw-r--r-- 1 1000 1000 2,9M 28 juin 11:09 /tmp/declare-P14
-rw-r--r-- 1 1000 1000 5,8M 28 juin 11:09 /tmp/declare-P15
-rw-r--r-- 1 1000 1000 12M 28 juin 11:09 /tmp/declare-P16
But by adding set -p to the subshell: