Category: Linux

Threads in bash 2

sheepchenLeave a comment

you want threads in bash and know exactly when they finish and in which state?

#!/bin/bash

threads=()
f_getThreadKeyword(){ for i in ${threads[@]}; do [[ $(echo $i|cut -d':' -f2) == $1 ]] && echo $(echo $i|cut -d':' -f1); done; }  # returns the keyword for a given pid
f_addThread(){ keyword=$1; pid=$2; threads+=( "$keyword:$pid" ); echo "added thread $keyword ($pid)"; }  # adds a thread to the array
f_removeThread(){ pid=$1; threads=( ${threads[@]/$(f_getThreadKeyword $pid):$pid} ); }  # removes a thread to the array
f_getThreadPids(){ echo ${threads[@]}|tr ' ' '\n'|cut -d':' -f2|tr '\n' ' '; }   # returns all pids


sleep 3 &
f_addThread first $!

sleep 10 &
f_addThread second $!

sleep 5 &
f_addThread third $!


while [[ $(jobs|grep -iE 'läuft|running' -c) -gt 0 ]]; do  # there are running background jobs
  wait -p next -n $(f_getThreadPids)
  err=$?
  echo pid $next exited with $err \($(f_getThreadKeyword $next)\)
  f_removeThread $next
done

echo done

Output:

added thread first (1429283)
added thread second (1429285)
added thread third (1429286)
pid 1429283 exited with 0 (first)
pid 1429285 exited with 143 (second)
pid 1429286 exited with 0 (third)

(I killed the second thread from another console)

massping script

sheepchenLeave a comment

just a little script which pings a defined number of servers a defined time and give you the result. Good for looking if you connection is stable or if it may be an internet problem.

#!/bin/bash

targets=( 1.1.1.1 8.8.8.8 cloudflare.com discord.com )
max=100


tmpfile=$$.massping.tmp

# functions
f_ping(){
  v=$(ping -c $max $1 2>/dev/null|grep received|cut -d' ' -f4)
  echo $1 $v >> $tmpfile
}

f_done(){
  [[ ! -f $tmpfile ]] && echo false && return
  [[ $(wc -l $tmpfile 2>/dev/null|cut -d' ' -f1) -eq ${#targets[@]} ]] && echo true && return
  echo false
}

# main
for s in ${targets[@]}; do
  f_ping $s &
done

c=$max; echo
while [[ $(f_done) == false ]]; do
  echo -e "\e[1A\e[Kwaiting. This should need $c more seconds.."
  c=$(( $c - 1 ))
  sleep 1
done
echo -e "\e[1A\e[Kdone"; echo

maxline=0; for w in $(cat $tmpfile|cut -d' ' -f1); do [[ ${#w} -gt $maxline ]] && maxline=${#w}; done
spaces=""; while [[ $(( ${#spaces} + 1 )) -lt $maxline ]]; do spaces="$spaces "; done
echo "server${spaces}%"
IFS="
"
while read -r line; do
  server=$(echo $line|cut -d' ' -f1)
  count=$(echo $line|cut -d' ' -f2)
  perc=$(echo "scale=1; $count * 100 / $max"|bc)
  spaces=""; while [[ $(( ${#spaces} + ${#server} - ( 5 - ${#perc} ) )) -lt $maxline ]]; do spaces="$spaces "; done
  echo "${server}${spaces} ${perc}"
done < $tmpfile

[[ -f $tmpfile ]] && rm -f $tmpfile

exampleoutput:

server             %
1.1.1.1        100.0
8.8.8.8        100.0
cloudflare.com  99.0
discord.com     85.0

threads in bash

sheepchenLeave a comment

Here an easy script for using threads in bash

#!/bin/bash

threads=4

thread(){
  echo "thread $$ started with param $1"
  sleep 10  # do stuff
}

selfcount(){ echo $(( $(ps -ef|grep -v grep|grep -c $0) - 3 )); }

for i in {1..100}; do   # worktasks
  while [[ $(selfcount) -ge $threads ]]; do
    sleep 0.1
  done
  thread $i &   # call thread in background
  sleep 0.1
done

while [[ $(selfcount) > 0 ]]; do sleep 0.1; done # wait for the last threads to finish

Create password for /etc/shadow

sheepchenLeave a comment

Sometimes you have to create a password-hash for the shadow-file. Here is an easy way to do it:

Method 1 (better suitable for scripting – passwort is visible)

openssl passwd -6 -salt xyz  yourpass

Method 2 (you enter in the PW – no clear text to see)

mkpasswd --method=SHA-512 --stdin

Note:
passing -1 will generate an MD5 password, -5 a SHA256 and -6 SHA512 (recommended)
The option --method accepts md5, sha-256 and sha-512

source: [stackexchange]