A list of handy bash commands

handy_bash.sh

# Bash Notes

# Silver search
ag -G "/settings.php" courses
ag -G "/version.php" format_grid /home/

# Search by type
cd /; sudo find . -depth -type d -name .gnupg

# Search plugin Moodle the fast way
ag block_coursespoints  --file-search-regex version.php --silent --ignore-case --skip-vcs-ignores --ignore={vendor,moodledata,public_old,node_modules} /home/

# FPM stats
top -bn1 | grep php-fpm


# Remove all except latest
ls -t | tail -n +2 | xargs -I {} rm {}
ls -t | tail -n +4 | xargs -I {} rm {}

# remove files older than a month in current directory
find . -mtime +40 -exec rm {} \;

#remove files older then a week
find . -mtime +7 -exec rm {} ;

# monitoring cpu and processes
ps -eo pcpu,pid,user,args | sort -k 1 -r | head -20

netstat -tanp

ps -efH

#dump all traffic to a file
tcpdump -i eth0 -s 65535 -w dump1.tcpdump

#remove files older then a week
find . -mtime +7 -exec rm {} \;

#remove files older than a month in current directory
find . -mtime +40 -exec rm {} \;

#dump all traffic to a file
tcpdump -i eth0 -s 65535 -w dump1.tcpdump

# Import mysql
time mysql --defaults-file=/etc/mysql/debian.cnf DATABASENAME < FILENAME.sql

# Snmp check
snmpwalk -v 2c -c public 192.168.1.1:163
snmpwalk -v 2c -c public 192.168.1.1:164

# replace all in directory.
 find /home/www/ -type f -exec sed -i 's/SEARCH/REPLACE/g' {} \;
 
# search in web files.
grep --include=\*.{css,php,js} -rnw $(pwd) -e "YourSearchText"

# find in content.
find . -name "*.php" -print | xargs grep "YourSearchText"

# MAIL
echo "content of mail body" | mail -s "Mail Server Tester" example@example.net

# Mysql import sql.
mysql --defaults-file=/etc/mysql/debian.cnf DB < FILE.sql


# Check cron errors
cat /var/log/syslog | grep cron

# Check if cron is working you will see a number
pgrep cron


# Check disk reads
sudo hdparm -tT /dev/sda

# Write
dd if=/dev/zero of=/tmp/output bs=8k count=10k; rm -f /tmp/output


# Interval a command
watch -n 60 php admin/cli/purge_caches.php

find . -type f -exec sed -i 's/192.168.86.91/192.168.32.21/g' {} \;

Reverse DNS
dig +noall +answer -x THEIP

stat -c '%a %n' *

Set new date on server for testing
date -s '2014-12-25 12:34:56'

grep -Rhi --with-filename "SSLCipherSuite" .

sed -i -- 's/php_admin_flag/#/g' *

Nameserver check

dig @8.8.8.8 NS domain.com

dig domain.com +noall +answer

System

uname -a # shows info about the system (kernel, architecture...)
sudo lshw # (only Linux) list all the hardware components
sudo lshw -short # (only Linux) list a summary table with the hardware components
lscpu # (only Linux) show information about the CPU
lsusb # (only Linux) list the plugged USB devices
date # print the current date and time

Processes

ps # shows the processes running right now on this terminal session
ps aux # shows all the processes running on the computer
htop # display an activity monitor in the terminal

Change users

su # change current user to root
su - # change current user and local variables to root
su maria # change current user to "maria"
sudo nano # runs command "nano" as root user

Filter the output

cat verylongfile.txt | more # shows the content of verylongfile.txt split in pages
cat verylongfile.txt | less # shows the content of verylongfile.txt split in pages, with support for scrolling and backwards navigation
cat verylongfile.txt | grep "I love you" # shows the lines where the string "I love you" is found

Variables and Path

echo "hello" # prints hello in the console
echo $USER # prints the value of the variable USER in the console

env # prints all the environment variables
set # prints all the local variables

MY_FRIENDS=William # create a local variable called MY_FRIENDS
MY_FRIENDS=$MY_FRIENDS:John:Anna # concatenate values 'John' and 'Anna' to MY_FRIENDS
export MY_FRIENDS # makes local variable MY_FRIENDS an environment one
unset MY_FRIENDS # deletes the variable MY_FRIENDS

export PATH=$PATH:/home/john/myprogram # add the directory /home/john/myprogram to the path

which nano # shows where is the executable of "nano" located
whereis nano # shows where are the executable, manuals, source code, etc. of "nano"

Directories

pwd # get current directory

cd # change current directory to home
cd /bin # change current directory to /bin
cd .. # go to parent directory

Directories

rmdir movies # remove the empty directory movies 
rm -rf movies # remove the directory movies and its files
rm file1.txt # remove the file file1.txt

mv /home/michael/myfile.txt /home/john/important.txt # move a file from /home/michael to /home/john
cp /home/michael/myfile.txt /home/john/important.txt # copy a file from /home/michael to /home/john
cp -R letters/ memories/ # copy the contents of the folder "letters" inside the folder "memories"
cp -R letters ~/Desktop # copy the folder "letters" to the Desktop


df -k . # free space in the current directory
df -k # free space in all the mounted volumes

Search / replace

find . -name hello.txt # finds a file called "hello.txt" in the current directory
find /home/joe/Downloads -name *.pdf # finds PDF files in the Downloads folder
find / -executable -atime -10 # find an executable file in the root directory that was accessed less than 10 minutes ago
find ~ -newer reference.txt # find a file in the home directory edited after the file "reference.txt"

sed -i "s|-Lsd|-LS4d|" /etc/default/snmpd

Compress and decompress TAR/ZIP files

# Tar / untar
tar -cvzf myfile.tar myfolder # compress the folder "my_folder" in the file "myfile.tar"
tar -xvzf myfile.tar # decompress the file myfile.tar in the current directory
tar -C /opt/abc -xvzf myfile.tar # decompress the file myfile.tar in /opt/abc

# Zip / unzip
zip -r myfile.zip myfolder # compress the folder "my_folder" in the file "myfile.zip"
unzip myfile.zip # decompress the file myfile.zip in the current directory

Reading Files

# grep: filter by lines
grep 455 sales.txt # print the lines where there is a 455

# cut: show some columns
cut -f 3 sales.txt # print only the third column
cut -f 2-3 sales.txt # print only the 2nd and 3rd columns
cut -c 9-19 sales.txt # for each line, print only from the 9th to the 19th character
cut -f 1 -d ';' clients.txt # the file clients.txt uses ';' as delimiter, instead a tab

# awk: the same than cut, but more flexible with delimiters, with more filters, and more computacionally complex
awk '{print $3}' sales.txt # print only the 3rd column
awk '{print $2 ", " $3}' sales.txt # print the 2nd and 3rd columns, separated with a comma
awk '{print $2 + $3}' sales.txt # print the sum of the 2nd and 3rd columns
awk 'length($0) > 20' sales.txt # print those lines whose length is longer than 20 characters
awk '$2 > 100' sales.txt # print those lines where the value of the second column is greater than 100

# wc
wc sales.txt # print the number of lines, words, and characters in the text file
ls -1 | wc # print the number of lines, words, and characters for each of the files in the current directory

# sort: sort the lines of a file according an alphabetic criteria
sort sales.txt # sort the lines of the file
sort -r sales.txt # sort the lines in reverse order
sort -R sales.txt # sort the lines in random order
sort -t $'\t' -k 3n,3 sales.txt # sort the lines numerically according the 3rd column

# uniq: shows the consecutive non-repeated or duplicated lines of a file
uniq hello.txt # skips consecutive duplicated lines
uniq -d hello.txt # show only consecutive duplicated lines
uniq -u hello.txt # show only lines that are not duplicated
uniq -c hello.txt # for each line, show the number of times it is duplicated

Monitoring

free -h -w -s 3 #Free memory

iotop # writes/reads disk
htop # Improved top 
iptraf # Wireshark alternative without GUI


journalctl -u snmpd --follow

SSL info

openssl s_client -showcerts -servername DOMAIN.nl -connect DOMAIN.nl:443

Speedtest

iperf3 -s 
iperf3 -c 192.168.32.10
iperf3 -c 192.168.32.1 -p 5200

<?php
$input = file_get_contents("php://input");
error_log(print_r($_REQUEST, true). PHP_EOL . $input, 3, __DIR__ . '/dump.txt');

Find installed plugins between 2 moodle folders

diff <(find public_html/ -printf '%P\n' | sort) <(find public_html_old/ -printf '%P\n' | sort) | grep '^[>]' | grep 'version.php' | rev | cut -c12- | rev