error function bash

using sed

function error {
  [ $( sed 's/\s/+/g' <<<${PIPESTATUS[*]} | bc ) -eq 0 ] && return || echo error && exit 1
}

using awk

function error {
  [ $( awk 'BEGIN{ OFS="+"} $1=$1; { print }' <<<${PIPESTATUS[*]} | bc ) -eq 0 ] && return || echo error && exit 1
}

top tools to monitoring performance on linux

top	display Linux processes
htop	interactive process viewer
iotop	simple top-like I/O monitor
iftop	display bandwidth usage on an interface by host
bmon	bandwidth usage monitor
atop	advanced system & process monitor
slabtop	display kernel slab cache information in real time

install virtualbox extension pack on linux

download extension pack from virtualbox.org

curl -O https://download.virtualbox.org/virtualbox/6.0.14/Oracle_VM_VirtualBox_Extension_Pack-6.0.14.vbox-extpack

install extension pack ( as root )

vboxmanage extpack install Oracle_VM_VirtualBox_Extension_Pack-6.0.14.vbox-extpack

list installed extensions pack

vboxmanage list extpacks

remove color from bash output

echo -e "\e[33;1mcolor\e[m" | sed 's/\x1b\[[0-9;]*m//g'

append text to standard input on linux

apeend a new line to stdin using cat

printf %s\\n ID-{1..3}' '{1..9..4} | cat <(echo c1 c2) -

join a text to stdin using bash

echo 1 2 3 | echo nums: $(</dev/stdin)

join a text to stdin using awk

awk '{ print "nums:", $0 }' <<< '1 2 3'

join a header text to stdin using awk

echo -e "a\nb\nc" | awk 'BEGIN{print "num"} {print $0}'

filter content on file maintaining the first line “header”

grep mail /etc/passwd | cat <(head -1 /etc/passwd) -

print output colored with sed

highlight matched input with color using sed

sed "s/root/$(tput setaf 1)&$(tput sgr0)/" /etc/passwd

Reference: http://linuxcommand.org/lc3_adv_tput.php

basename and dirname commands implemented in awk

basename implementation using awk. Get only filename

awk 'sub( /\/.*\//,"",$0 )' <<< '/usr/bin/ls'

dirname implementation using awk. Get only directory path

awk 'sub( /\/[a-z]*$/,"",$0 )' <<< '/usr/bin/ls'

rotate screen linux

rotate screen to the left

xrandr --output $( xrandr | awk '/ connected/ {print $1}' ) --rotate left

back screen to normal mode

xrandr --output $( xrandr | awk '/ connected/ {print $1}' ) --rotate normal

show progress while copy file in linux

pv fileName > /path/to/destination/dir/fileName

history of ssh logins/connections

On Debian

grep 'ssh.*Accepted password.*ssh.$' /var/log/auth* | cut -d: -f2- | column -t

On CentOS

grep 'ssh.*Accepted password.*ssh.$' /var/log/secure* | cut -d: -f2- | column -t

split and join a big file in linux

split a iso file with 4.5GB into 2 files

split -b 2500M image.iso image.iso_part-

join splited files, recreating original file

cat image.iso_part-* > new_image.iso

check integrity of the file

md5sum image.iso new_image.iso