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Run cmd1, then if cmd1 successful run cmd2, otherwise skip.
cmd1 && cmd2
Run cmd1, then if cmd1 not successful run cmd2, otherwise skip.
cmd1 || cmd2
Do cmd1 and then cmd2.
cmd1; cmd2
Do cmd1, start cmd2 without waiting for cmd1 to finish.
cmd1 & cmd2
clears content on window (hide displayed lines)
clear
shows the manual for specified command
man
Shortcuts
halts the current command
Ctrl+C
stops the current command, resume with fg in the foreground or bg in the background
Ctrl+Z
Delete the current word / argument left of the cursor
Ctrl+W
cuts everything before the cursor
Ctrl+U
search previous typed commands
Ctrl+R
log out of current session
exit
Ctrl+D
full window program
cmd+up
not full window program
cmd+down
undo
ctrl+_
swap two characters
ctrl+t
swap two words
ALT+t
prints last argument from previous command
ALT+.
expand glob/star
ctrl+x+*
move forward a word
ctrl+arrow
move forward a word
ALT+f
move backward a word
ALT+b
opens the command string in an editor so that you can edit it before execution
ctrl+x+ctrl+e
move to the opposite end of the line
ctrl+xx
cuts everything after the cursor
ctrl+k
pastes from the buffer
ctrl+y
clears screen and redisplay the line
CTRL+L
same as RETURN
CTRL+J
same as RETURN
CTRL+M
next line in command history
CTRL+N
same as RETURN, then displays next line in history file
CTRL+O
previous line in command history
CTRL+P
searches forward
CTRL+S
lists the possible filename completefions of the current word
CTRL+X
Move to beginning of line
Ctrl+A
Move to end of line
Ctrl+E
Directory & Navigation
create a new directory
mkdir
changes to home
cd
changes directory
cd
tells you where you currently are
pwd
Go to previous directory
cd -
delete directory dir
sudo rm -r dir
force remove directory dir *
sudo rm -rf dir
copy dir1 to dir2; create dir2 if it doesn't exist
cp -r dir1 dir2
Finds a file/directory
find filename dir
Find files from root rirectory
find / -name wordToFind*
List files that match the reg. exp. from current folder
find . -name wordToFInd
Shows the location of a file
whereis filename
Shows the location of a file if it is in your PATH
which filename
Jobs
Step 1, write in the terminal: at ENTER ex --> at 16:45 or at 13:43 7/23/11 (to be more precise) or after a certain delay: at now +5 minutes (hours, days, weeks, months, years) Step 2: ENTER repeat step 2 as many times you need Step 3: CTRL D to close input atq = show a list of jobs waiting to be executed atrm = delete a job n. ex (delete job #42) --> atrm 42 sleep = pause between commands with ";" you can chain commands, ex: touch file; rm file you can make a pause between commands (minutes, hours, dys) ex --> touch file; sleep 10; rm file <-- 10 seconds
execute a command regularly
crontab
modify the crontab
crontab -e
view current crontab
crontab -1
delete you crontab
crontab -r
Crontab syntax
<Day of week (0-6, 0 = Sunday)>
ex, create the file movies.txt every day at 15:47
47 15 * * * touch /home/bob/movies.txt
every minute
at 5:30 in the morning,from the 1st to 15th each month:
30 5 1-15 * *
at midnight on Mondays, Wednesdays and Thursdays:
0 0 * * 1,3,4
Execute programs in the background
Add a '&' at the end of a command
cp bigMovieFile.mp4 &
nohup: ignores the HUP signal when closing the console (process will still run if the terminal is closed)
nohup cp bigMovieFile.mp4
lists all jobs / what is running in the background (use with -l to see associated PID)
jobs
put a background process to foreground
fg (process 1), f%2 (process 2) f%3, ...
lists stopped or background jobs ; resume a stopped job in the background
bg
brings the most recent job in the foreground
fg
brings job to the foreground
fg
To suspend a job, type CTRL+Z while it is running. You can also suspend a job with CTRL+Y.
This is slightly different from CTRL+Z in that the process is only stopped when it attempts to read input from terminal.
Of course, to interupt a job, type CTRL+C.
runs job in the background and prompts back the shell
myCommand &
brings most recently invoked background job
fg %+
brings second most recently invoked background job
fg %-
brings job number N
fg %N
brings job whose command begins with string
fg %string
brings job whose command contains string
fg %?string
removes the process from the list of jobs
disown <PID|JID>
waits until all background jobs have finished
wait
brings job n to the foreground
fg n
Scheduling a shutdown
wait 60 mins before starting the shutdown
sudo shutdown -P +60
shutdown at 1 AM
sudo shutdown -P 1:00
Cancel a pending shutdown
sudo shutdown -c
Run command at specific time
echo "ls -l" | at 07:00
I/O Redirection
Output of pgm is redirected to file.
pgm > file
python hello.py > output.txt
Program pgm reads its input from file. (takes standard input from file)
pgm < file
feed foo.txt to stdin for python
python hello.py < foo.txt
Output of pgm is appended to file.
pgm >> file
python hello.py >> output.txt
Output of pgm1 is piped into pgm2 as the input to pgm2.
pgm1 | pgm2
Standard input comes from here through next tag at start of line.
<< tag
Note that file descriptor 0 is normally standard input, 1 is standard output, and 2 is standard error output.
forces standard output to file even if noclobber is set
|file
forces output to file from file descriptor n even if noclobber is set
n>|file
uses file as both standard input and standard output
<> file
uses file as both input and output for file descriptor n
n<>file
Merge output from stream n with stream m.
n >& m
Merge input from stream n with stream m.
n <& m
duplicates standard output to file descriptor n
n>&
duplicates standard input from file descriptor n
n<&
directs standard output and standard error to file
adds your ssh key to host for user to enable a keyed or passwordless login
ssh-copy-id user@host
Network
displays whois online
w
pings host and outputs results
ping
gets whois information for domain
whois
gets DNS information for domain
dig
reverses lookup host
dig -x
downloads file
wget
ping host and output results
ping host
continue a stopped download
wget -c file
User and Group
who you are logged in as
whoami
lets you change your password
passwd
displays information about user
finger
Example: Display information about the user ch. Output will appear similar to the following:
finger -p ch
Login name: admin In real life: Computer Hope On since Feb 11 23:37:16 on pts/7 from domain.computerhope.com 28 seconds Idle Time Unread mail since Mon Feb 12 00:22:52 2001
lists your last logins
last
User and Group Quotas
Definition
The user and group quotas provide the mechanisms by which the amount of space used by a single user or all users within a specific group can be limited to a value defined by the administrator.
- Soft Limit − If the user exceeds the limit defined, there is a grace period that allows the user to free up some space.
- Hard Limit − When the hard limit is reached, regardless of the grace period, no further files or blocks can be allocated.
Displays disk usage and limits for a user of group
quota
This is a quota editor. Users or Groups quota can be edited using this command
edquota
Scans a filesystem for disk usage, creates, checks and repairs quota files
quotacheck
This is a command line quota editor
setquota
This announces to the system that disk quotas should be enabled on one or more filesystems
quotaon
This announces to the system that disk quotas should be disabled for one or more filesystems
quotaoff
This prints a summary of the disc usage and quotas for the specified file systems
repquota
list all users available
who
root creates new user
sudo adduser bob
change a user's password
sudo passwd
Delete an account
sudo deluser
reate a new user group
addgroup friends
delete a user group
delgroup friends
add user to a group
usermod -g friends
change account name
usermod -g bob boby
add groups to a user without loosing the ones he's already in
usermod -aG friends bob
System
shows kernel information
uname -a
Memory & Process Management
cpu information
cat /proc/cpuinfo
memory information
cat /proc/meminfo
show memory and swap usage
free
process's from current user
ps -u yourusername
kill all processes with the name
killall
displays your currently active processes dinamically
top
prints process ID of the current shell
echo $$
prints process ID of the most recently invoked background job
echo $!
returns a list of all signals on the system, by name and number
kill -l
terminates process with specified PID
kill
selects all processes with a tty except session leaders
ps -a
executes a command when a signal is received by the script
trap cmd sig1 sig2
ignores that signals
trap "" sig1 sig2
resets the action taken when the signal is received to the default
trap - sig1 sig2
display your currently active processes
ps
List processes sorted
ps aux --sort -rss
display all running processes
top
select all processes
ps -e
kill process
killall UnResponsiveProg
Kill all processes matching the string "unresponsiveprog" (ignoring the difference between upper- ## lowercase letters)
killall -I unresponsiveprog
violent kill
kill -9
graphic representation of system load average (quit with CTRL C)
tload
View and Manage Processes
htop
Suspend and send to background
Ctrl + z
Then
bg
Get a process back to the foreground again
fg
Date & Time
shows the current date and time
date
shows current uptime
uptime
show this month's calendar
cal
show current uptime
uptime
List current day Events (calendar)
calendar
Output date
ex: 12-Mar-2004
date +%d-%b-%Y
today=$(date +%d-%b-%Y) && echo $today
If it's 9 am, then it will show 09
date “+%H”
Applications
show possible locations of app
whereis app
show which app will be run by default
which app
list all directories were installation script might added files
grep -P '("|/)\S+/\S+' setup.sh
run a program/app
sudo %program%
sudo program -l
remove application
sudo apt-get remove <application_name>
When software is available in the repositories:
sudo apt-get install
ex
sudo apt-get install aptitude
downloaded package
sudo dpkg --install
ex
sudo dpkg --install megasync-xUbuntu_17.04_amd64.deb
If you download it from the Internets in .gz format
(or bz2) - “Compiling from source”
Step 1, create a folder to place the file:
mkdir /home/username/src <-- then cd to it
Step 2, with 'ls' verify that the file is there
(if not, mv ../file.tar.gz /home/username/src/)
Step 3, decompress the file (if .zip: unzip )
Step 4, use 'ls', you should see a new directory
Step 5, cd to the new directory
Step 6.1, use ls to verify you have an INSTALL file,
then: more INSTALL
If you don't have an INSTALL file:
Step 6.2, execute./configure <-- creates a makefile
Step 6.2.1, run make <-- builds application binaries
Step 6.2.2 : switch to root --> su
Step 6.2.3 : make install <-- installs the software
Step 7, read the readme file
Install from source
./configure
make
make install
install a package (Debian)
dpkg -i pkg.deb
install a package (RPM)
rpm -Uvh pkg.rpm
shows the disk usage of the files and directories in filename (du -s give only a total)
du
du -s
show disk usage
df
show directory space usage
du
The -h option makes the output easier to comprehend
du -h /etc
(disk free) displays the disk space usage in kilobytes
df -k
History
Commands
Show history
history
Don’t execute expanded result immediately
shopt -s histverify
Expansions
Expand last parameter of most recent command
!$
Expand all parameters of most recent command
!*
Expand nth most recent command
!-n
Expand nth command in history
!n
Expand most recent invocation of command
!
Operations
Execute last command again
!!
sudo !!
Replace first occurrence of to in most recent command
!!:s///
Replace all occurrences of to in most recent command
!!:gs///
Expand only basename from last parameter of most recent command
!$:t
Expand only directory from last parameter of most recent command
!$:h
Note: !! and !$ can be replaced with any valid expansion.
Slices
Expand only nth token from most recent command (command is 0; first argument is 1)
!!:n
Expand first argument from most recent command
!^
Expand last token from most recent command
!$
Expand range of tokens from most recent command
!!:n-m
Expand nth token to last from most recent command
!!:n-$
!! can be replaced with any valid expansion i.e. !cat, !-2, !42, etc.
Easily search and use the commands that you had used in the past
ctrl+r search_term
Other Shell Features
Command-Line Processing Cycle.
The default order for command lookup is functions, followed by built-ins, with scripts and executables last.
There are three built-ins that you can use to override this order: command, builtin and enable.
removes alias and function lookup. Only built-ins and commands found in the search path are executed
command
looks up only built-in commands, ignoring functions and commands found in PATH
builtin
enables and disables shell built-ins
enable
takes arguments and run them through the command-line processing steps all over again
eval
Create command alias
cd; nano .bash_profile
alias gentlenode='ssh [email protected] -p 3404' # add your alias in .bash_profile
Using alias to fix typos
alias gerp=grep
To quickly go to a specific directory
cd; nano .bashrc
shopt -s cdable_vars
export websites="/Users/mac/Documents/websites"
source .bashrc
cd websites
