grab Apple DEVELOPMENT_TEAM ID from Keychain

devteamid.sh

#!/usr/bin/env bash

CODESIGN_CN_STRING='Developer ID Application'
#CODESIGN_CN_STRING='Apple Development'

#requires openssl@3 from Homebrew
_openssl=$(brew --prefix openssl 2>/dev/null)/bin/openssl
[[ -x $_openssl ]] || { echo "missing openssl, try \`brew install openssl\`"; exit 1; }

#find development cert
csids=$(security find-identity -v -p codesigning | grep -E '[A-F0-9]{40}')
[[ -n $csids ]] || { echo 1>&2 "could not find codesigning identity"; exit 1; }
read -r sha1 cn _ < <(sed -En "s/^.*([A-F0-9]{40}).*$CODESIGN_CN_STRING.*\((.*)\).*$/\1 \2/p" <<<"$csids")
[[ -n $cn && -n $sha1 ]] || { echo 1>&2 "could not find valid development cert"; exit 1; }

#make temp dir
outdir=$(mktemp -d /private/tmp/teamid.XXXXXX)
[[ -n $outdir ]] || { echo "error creating temp dir"; exit 1; }

#export cert
if ! security find-certificate -a -c "$cn" -Z -p >"${outdir}/${cn}.pem"; then
  echo "error exporting cert from Keychain"
  exit 1
fi

#check for hash match
certhash=$(awk -v h="$sha1" '$0 ~ "^SHA-1 hash: " h {print $NF; exit}' "${outdir}/${cn}.pem")
[[ $certhash == "$sha1" ]] || { echo "hash mismatch! ($certhash vs $sha1)"; exit 1; }

#output DEVELOPMENT_TEAM
$_openssl x509 -in "${outdir}/${cn}.pem" -subject -noout |
sed -En 's/.*OU ?= ?([^,]+),.*$/\1/p'

#cleanup
rm -r "${outdir:?}"

src: https://stackoverflow.com/a/70464809/617864