wpa_supplicant end process if wrong password detected

Question

Normally when I run wpa_supplicant I'll get some output like this:

Successfully initialized wpa_supplicant
ioctl[SIOCSIWAP]: Operation not permitted
ioctl[SIOCSIWENCODEEXT]: Invalid argument
ioctl[SIOCSIWENCODEEXT]: Invalid argument
wlan3: Trying to associate with 9c:3d:cf:fb:95:96 (SSID='Bell420' freq=2462 MHz)
wlan3: Association request to the driver failed
wlan3: Associated with 9c:3d:cf:fb:95:96
wlan3: Authentication with 9c:3d:cf:fb:95:96 timed out.
ioctl[SIOCSIWAP]: Operation not permitted
wlan3: CTRL-EVENT-DISCONNECTED bssid=9c:3d:cf:fb:95:96 reason=3 locally_generated=1
wlan3: WPA: 4-Way Handshake failed - pre-shared key may be incorrect

The problem is it just keeps trying over and over.

Is there a way I can tell wpa_supplicant to quit as soon as it gets an obvious error like wrong key?

I'm on an older embedded device with wpa_supplicant v2.1.

---

I wrote a workaround for monitoring wpa_supplicant for incorrect keys. Using grep on wpa_supplicant (with stdbuf based on Stéphane Chazelas' comment here):

  # Create conf file with ssid and password
  wpa_passphrase "$ssid" "$password" > /etc/wpa_supplicant/wpa_supplicant.conf

  # If wifi key is wrong kill subshell
  subshell=$BASHPID
  (sudo stdbuf -o0 wpa_supplicant -Dwext -iwlan1 -c/etc/wpa_supplicant/wpa_supplicant.conf 2>&1 \
    | grep -m 1 "pre-shared key may be incorrect" \
    && kill -s PIPE "$subshell") &

Note: the above block is inside a subshell in a script.

It seemed to work initially but over time I found sometimes it would cause the whole script to fail when the password was fine. Other times it would work as expected.

There must be a better way to do this.

---

Edit: Maybe I should be using wpa_cli here instead?

Answer 1

#!/bin/bash

# SSID and password
ssid="YourSSID"
password="YourPassword"

# Create wpa_supplicant.conf
wpa_passphrase "$ssid" "$password" > /etc/wpa_supplicant/wpa_supplicant.conf

# Run wpa_supplicant in the background
wpa_supplicant -Dwext -iwlan1 -c/etc/wpa_supplicant/wpa_supplicant.conf > /tmp/wpa_supplicant.log 2>&1 &

# Monitor log file for error messages
tail -f /tmp/wpa_supplicant.log | while read -r line; do
    if [[ $line == *"pre-shared key may be incorrect"* ]]; then
        echo "Incorrect key detected. Exiting..."
        kill $!
    fi
done

wpa_supplicant is run in the background, and its output is redirected to a log file. The tail command continuously reads the log file and checks for the specified error message. If the error message is found, it prints a message and terminates the script by killing the wpa_supplicant process.