A shell script to enable sudo by "Touch ID" on macOS

enable_sudo_by_touch_id.sh

#!/bin/sh
# A shell script to enable sudo by "Touch ID" on macOS
# tested on macOS 11.6 Big Sur
TARGET_FILE=/etc/pam.d/sudo 

# skip if it is not run on macOS
if [ 'Darwin' != `uname` ]; then
	echo "not on macOS platform. exit."
	exit 0
fi

# check target file
grep "auth       sufficient     pam_tid.so" $TARGET_FILE > /dev/null 

if [ $? -ne 1 ]; then
	echo "already has pam_tid.so line in ${TARGET_FILE}. do nothing."
	exit 0
fi

# edit file with sed command. 
# with -i option, sed creates backup file on the same directory.

sudo chmod +w ${TARGET_FILE}
sudo sed -i '.bak' -e '2 i\
auth       sufficient     pam_tid.so' ${TARGET_FILE}
if [ $? -ne 0 ]; then
	echo "an error occured. exit."
    exit 0
fi

sudo chmod -w ${TARGET_FILE}

echo "succeeds. see ${TARGET_FILE}."

cat ${TARGET_FILE}