open terminal: Ctrl+Alt+T
Ctrl + C is used to kill a process with signal SIGINT , in other words it is a polite kill .
Ctrl + Z is used to suspend a process by sending it the signal SIGTSTP , which is like a sleep signal, that can be undone and the process can be resumed again.
Ctrl+D: log out of current session, similar to exit.
history | grep "command looking for"
-
Ctrl+R – type to bring up a recent command
-
!! - repeats the last command
-
exit – log out of current session
-
fg in the foreground or bg in the background
-
Ctrl+W – erases one word in the current line
-
Ctrl+U – erases the whole line
Change password for user
passwd user
sudo groupadd ic-api
sudo usermod -g ic-api ic-api
find . -type f -name "*.conf"
Example:
grep -lr 'gceu' .
grep pattern dir - Search for pattern in dir.
Flags:
-l (or --files-with-matches) option is used to only print filenames of matching files, and not the matching lines (this could also improve the speed, given that grep stop reading a file at first match with this option).
-r recursive
-i ignore-case
--include search only files that match the file pattern
grep -ril --include \*.py --include \*.html ".id"
- command | grep pattern – search for pattern in the output of command
https://www.thegeekstuff.com/2011/10/grep-or-and-not-operators/
grep 'pattern1\|pattern2' filename
grep -E 'pattern1|pattern2' filename
grep -B 4 -A 4
Find all instances of file
locate file
- cal – show this month's calendar
- uptime – show current uptime
- w – display who is online
- whoami – who you are logged in as
- finger user – display information about user
- htop - a lightweight text-mode process viewer packed with handy features such as killing processes without entering their PID, displaying full command lines, etc with a colour display
Show kernel information
uname -a
Ubuntu
lsb_release -a
CentOS
hostnamectl
cat /proc/cpuinfo
Show number of cores only
grep -c ^processor /proc/cpuinfo
cat /proc/meminfo
Show memory and swap usage, show output in gigabytes.
free -g
Show the current date and time, in the format of: date+"T"+hour+minute+second+UTC time zone offset
$ date +"%FT%H%M%S%z"
2019-02-19T104943+1100
https://www.cyberciti.biz/faq/linux-display-date-and-time/
df -h
show disk usage with human readable unit.
du -h --max-depth=1
show directory space usage, only one level deep.
ip a
One line command to just grep the ip:
ip a | grep "scope global" | grep -Po '(?<=inet )[\d.]+'
For older version of centOS:
ifconfig | grep "inet " | grep -v 127.0.0.1 | awk '{print $2}'
CentOS older
netstat - Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships
-a, --all Show both listening and non-listening (for TCP this means established connections) sockets. With the --interfaces option, show interfaces that are not up
--numeric , -n Show numerical addresses instead of trying to determine symbolic host, port or user names.
-p, --program Show the PID and name of the program to which each socket belongs.
netstat -anp | grep :8
https://www.centos.org/docs/5/html/5.1/Deployment_Guide/s1-server-ports.html
CentOS 7 netstat, which is part of the package net-tools has been officially
deprecated, so you should be using ss (part of the package iproute2),
going forward.
ss -anp | grep :8443
https://unix.stackexchange.com/a/385500/36816
ss -lnpt 'sport = :3000'
-l, --listening Display only listening sockets (omitted by default).
-n, --numeric Do not try to resolve service names.
-p, --processes Show process using socket.
-t, --tcp Display TCP sockets.
https://unix.stackexchange.com/questions/106561/finding-the-pid-of-the-process-using-a-specific-port
journalctl -u nginx.service --since today
printenv
printenv DBPASS
or
echo $TERM
The dollar sign $ can actually be used to combine the values of environment variables in many shell commands. For example, the following command can be used to list the contents of the "Desktop" directory within the current user's home directory.
ls $HOME/Desktop
Add var into this file:
sudo -H nano /etc/environment
It's important to do exact the way above, and not as the root user, as it may cause problems like unable to login. If you use normal sudo to start graphical applications (including editors e.g. gedit), sometimes it results in the configuration files being owned by root, read more about it here.
The only time the file is read is on login, when the PAM stack is activated – specifically pam_env.so, which reads the file.
Logging out and back in would apply the changes – and in fact you must do this if you want all your processes to receive the new environment. All other solutions will only apply the environment to the single shell process, but not to anything you launch through the GUI including new terminal windows.
which app
show which app will be run by default
man command
show the manual for command
- whereis app – show possible locations of app
miranda-zhang/bash.md
https://gist.github.com/miranda-zhang/9871f934edbb87a23c11185b85e191be
- cd dir - change directory to dir
- cd – change to home
- pwd – show current directory
- mkdir dir – create a directory dir
- rm file – delete file
- rm -r dir – delete directory dir
- rm -f file – force remove file
- rm -rf dir – force remove directory dir *
- cp file1 file2 – copy file1 to file2
- cp -r dir1 dir2 – copy dir1 to dir2; create dir2 if it doesn't exist
- mv file1 file2 – rename or move file1 to file2 if file2 is an existing directory, moves file1 into directory file2
- touch file – create or update file
- cat > file – places standard input into file
- more file – output the contents of file
- head file – output the first 10 lines of file
- tail file – output the last 10 lines of file
- tail -f file – output the contents of file as it grows, starting with the last 10 lines
xdg-open .
https://askubuntu.com/a/31196/202823
show hidden files with-a, show details with -l
ls -al
Determine file type, i.e. check if somthing is a symbolic link.
file
Counting Files in the Current Directory
ls -1 | wc -l
This uses wc to do a count of the number of lines (-l) in the output of ls -1. http://tldp.org/HOWTO/Bash-Prompt-HOWTO/x700.html
- chmod octal file – change the permissions of file to octal, which can be found separately for user, group, and world by adding:
- 4 – read (r)
- 2 – write (w)
- 1 – execute (x)
Examples:
- chmod 777 – read, write, execute for all
- chmod 755 – rwx for owner, rx for group and world
- tar cf file.tar files – create a tar named file.tar containing files
- tar xf file.tar – extract the files from file.tar
- tar czf file.tar.gz files – create a tar with Gzip compression
- tar xzf file.tar.gz – extract a tar using Gzip
- tar cjf file.tar.bz2 – create a tar with Bzip2 compression
- tar xjf file.tar.bz2 – extract a tar using Bzip2
- gzip file – compresses file and renames it to file.gz
- gzip -d file.gz – decompresses file.gz back to file
- top – display all running processes
- kill pid – kill process id pid
- killall proc – kill all processes named proc *
- bg – lists stopped or background jobs; resume a stopped job in the background
- fg – brings the most recent job to foreground
- fg n – brings job n to the foreground
Display your currently active processes
Show full command including arguments.
$ ps -p [PID] -o args
- ping host – ping host and output results
- whois domain – get whois information for domain
- dig domain – get DNS information for domain
- dig -x host – reverse lookup host
- wget file – download file
- wget -c file – continue a stopped download
Debian
dpkg -i pkg.deb
RPM
rpm -Uvh pkg.rpm
CentOS
yum install pkg
Ubuntu apt update apt upgrade apt install pkg
Node.js, Javascript package manager
npm install
- ./configure
- make
- make install
Possible log location
/var/log/audit/audit.log
grep "denied" /var/log/audit/audit.log
Graph with gnuplot interactively:
apt update
apt install gnuplot-x11
gnuplot
# SET TERMINAL
set term gif
set output 'frequency.gif'
# set title "Word Frequency"
# Axes label
# set xlabel "Words"
# set ylabel "Frequency"
set xtics rotate by -90
plot "frequency.dat" using 1:xticlabels(2) with boxeshttps://shapeshed.com/unix-ln/#how-to-create-a-symbolic-link
Create symbolic link link to file
ln -s source_file link
Without -s, then create hard link.