Shell Programming and Scripting

#!/bin/bash

function gui_start {
    local choice=""
    choice=`yad --title="TITLE" --center --text="WELCOME insert text" --entry`
    verify_exit "$?"
    
    if [ "$choice" == "a" ]; then
        gui="gui_1"
    else
        gui="gui_1"
    fi

    "$gui" | fun_1 | yad --title="This is the list" --center --list --column="First":TEXT
}

function gui_1 {
    local x=""
    x=`yad --text="Insert a number" --entry`
    verify_exit $?
    
    if [ "$x" == "" ]; then
        exit
    fi
    
    while [ $x -ne 0 ]
    do
        echo "aaa bbb"
        x=$(($x-1))
    done
}

function fun_1 {
    while read input
    do
        echo "$input"
    done
}

function verify_exit {
    local code="$1"
    if [ "$code" -eq 1 -o "$code" -eq 252 ]; then
        kill_all_child $MY_PID
    fi
}

function kill_all_child {
    local parent=$1
    local childs=""

    local com="ps -Al | grep -w $parent | awk '{print \$4}'"
    childs=`eval $com`

echo "process pid: $parent"
echo "childs: $childs"

    local j=0

        for i in $childs
        do
            if [ $j -ne 0 ]; then #Skip the first pid in $childs that is the current process id
                kill_all_child "$i"
            fi
            j=$(($j+1))
        done

    kill -kill $parent
}

MY_PID=$$
gui_start

$ ps -Al
...
0 S  1002 21515 21512  0  80   0 - 28022 wait   pts/3    00:00:00 my-search-tool
1 S  1002 21519 21515  0  80   0 - 28022 pipe_w pts/3    00:00:00 my-search-tool
1 S  1002 21520 21515  0  80   0 - 28022 pipe_w pts/3    00:00:00 my-search-tool
0 S  1002 21521 21515  0  80   0 - 104391 poll_s pts/3   00:00:00 yad
0 S  1002 21522 21519  1  80   0 - 104357 poll_s pts/3   00:00:00 yad

...

#First call to KILL_ALL_CHILDS
process pid: 21515
childs: 21515 21519 21520 21521

#Second call
process pid: 21519
childs: 21519 21598 #Why 21598 ? Is not in the output of ps -Al of before ?! And why there is not 21522 ??

#Third call
process pid: 21598
childs: 

#And here i get the error:
./my-search-tool-2: line 67: kill: (21598) - No such process

$ ps -Al
0 S  1002 24241 24184  0  80   0 - 28022 wait   pts/1    00:00:00 my-search-tool
1 S  1002 24243 24241  0  80   0 - 28022 pipe_w pts/1    00:00:00 my-search-tool
1 S  1002 24244 24241  0  80   0 - 28022 pipe_w pts/1    00:00:00 my-search-tool
0 S  1002 24245 24241  1  80   0 - 104428 poll_s pts/1   00:00:00 yad
0 S  1002 24246 24243  0  80   0 - 104357 poll_s pts/1   00:00:00 yad

$ EXTERNAL_KILL_ALL_CHILD 24241
mypid: 24241
childs: 24241 24243 24244 24245

mypid: 24243
childs: 24243 24246

mypid: 24246
childs: 24246

mypid: 24244
childs: 

Desktop/EXTERNAL_KILL_ALL_CHILDS: line 20: kill: (24244) - No such process

mypid: 24245
childs: 24245

pkill -TERM -P $$