Script to extract and convert associated on frequencies to channel numbers from a wpa_supplicant log

associated_freqs.sh

#!/bin/sh
# Author: TBK
# Email: tbk@jjtc.eu
# SPDX-License-Identifier: GPL-2.0-only
# Version: 0.0.1
# Description: Tool to extract and nicely present channels that wpa_supplicant has associated on
# Usage: ./associated_freqs.sh

if [ -f wpa_supplicant.log ]; then
    # Grab all lines with frequencies that has been associated on | Reduce it to the frequency | Sort | Remove duplicates
    grep -E "^.*nl80211: Associated on.*$" wpa_supplicant.log | cut -d " " -f5-6 | sort | uniq > associated_frequencies.txt

    # Original code - https://github.com/torvalds/linux/blob/master/net/wireless/util.c#L141
    ieee80211_freq_mhz_to_channel() {
        freq="$1"

        # see 802.11 17.3.8.3.2 and Annex J
        if [ "$freq" -eq 2484 ]; then
            return 14
        elif [ "$freq" -lt 2484 ]; then
            return $(((freq - 2407) / 5))
        elif [ "$freq" -ge 4910 ] && [ "$freq" -le 4980 ]; then
            return $(((freq - 4000) / 5))
        elif [ "$freq" -lt 5925 ]; then
            return $(((freq - 5000) / 5))
        elif [ "$freq" -eq 5935 ]; then
            return 2
        elif [ "$freq" -le 45000 ]; then
            # DMG band lower limit
            # see 802.11ax D6.1 27.3.22.2
            return $(((freq - 5950) / 5))
        elif [ "$freq" -ge 58320 ] && [ "$freq" -le 70200 ]; then
            return $(((freq - 56160) / 2160))
        else
            return 0
        fi
    }

    # Debug
    #ieee80211_freq_mhz_to_channel 2484
    #echo "Should return 14 - $?"

    # Time to style the result
    rm -f associated_frequencies-tmp.txt
    channels=""
    while read l; do
        f=$(printf "$l" | cut -d " " -f1)
        ieee80211_freq_mhz_to_channel "$f"
        channel="$?"
        channels="${channels}${channels:+,}$channel"
        printf "%s MHz - %s\n" "$f" "$channel" >> associated_frequencies-tmp.txt
    done < associated_frequencies.txt

    ## Add string of the channels that can be used in wpa_sup config directly
    printf "\n\nChannels: %s\n" "$channels" >> associated_frequencies-tmp.txt

    rm -f associated_frequencies.txt
    mv associated_frequencies-tmp.txt associated_frequencies.txt

    printf '\nContent of associated_frequencies.txt:\n'
    cat associated_frequencies.txt

    exit 0
else
    printf 'Wooh! wpa_supplicant.log needs to be present!\n'
    exit 1
fi