- Common commands
- Special characters
- Keyboard shortcuts
- Other shortcuts
- Environment Variables
- Changing Shells
- Search for processes and then kill them
- Linux directories
| command | description |
|---|---|
--help |
type this after a command to see the help (try git push -u --help) |
alias wa="whatis" |
create keyboard shortcuts for common commands. Run alias alone to list all aliases. Note these are not persistent...use .bashrc or .bash_aliases for that. Note that if you are using variables in your alias, single quotes will resolve the variable when the alias is invoked (e.g. alias p='$PATH') whereas double quotes will resolve the value when the alias is defined and keep that value (e.g. alias p="$PATH"). |
apropos |
find what man page is appropriate |
cal |
show a calendar |
cat |
output the entire contents of a file (e.g. cat test.txt). Note you can output multiple files (e.g. cat test1.txt test2.txt) |
cat -n |
print the contents with line numbers |
cd |
change directory |
cd - |
go to last directory |
cd .. |
go up one directory (two directories: cd ../..) |
cd ~ |
go to home directory |
cd / |
go to the root directory |
chmod |
change file access permissions e.g. chmod 755 README.py (see permissions.md) |
chown |
change the owner and group of a file or directory (e.g. sudo chown -R jessica Files/ to change the owner or sudo chown -R jessica:everyone Files/ to change both owner and group –note the -R is for recursive) |
clear |
clear the terminal display (or control L) |
cp |
copy a file or directory |
cp -r Notes Notes_copy |
duplicates the Notes directory and its contents as Notes_copy |
cp file1.txt backup/ |
creates a copy of file1 in a directory called backup |
cp file1.txt file2.txt |
copies file1 and creates file2 |
date |
print out the current date |
diff |
compare difference between files |
diff -y |
to display diffs side by side |
diff -u |
to display diffs unified in one blob (similar to a git diff) |
dirs |
used with pushd and popd to see which directories are on the stack |
du -h |
disc usage... outputs sizes in the current directory |
du -h | sort -hr | head |
output the 10 largest files or directories in the current directory |
df -h |
displays free disk space |
echo |
print some arguments (e.g. echo $PATH) |
echo "USERNAME=ADMIN" > config.txt |
creates a new file if not exists with content USERNAME=ADMIN |
env |
look at your environment |
exit |
exit the shell |
export |
export/set a new environment variable |
find |
find files (see man find) |
find . -name 'README.md' |
find all files (recursively) in the current directory called README.md |
find . -type d -name 'venv' |
find all directories (recursively) in the current directory called venv |
find . -type d -name 'venv' -or -name 'node_modules' |
find all directories called venv or node_modules |
find . -name 'README.md' -not -path '*node_modules*' |
find and exclude paths with -not -path |
find . -type f -mtime - |
find files modified in the last 24hrs |
find . -type f -size +10M |
find files 10mb or greater. Units can be: k, M, G, T, P for kilobytes, megabytes, gigabytes, terabytes, petabytes |
grep |
find things inside files (e.g. grep '<body>' index.html) |
grep -r |
searches for files in directories that are within other directories (by default grep only searches the current directory, not sub directories) |
grep -i mountains |
search for mountains, case insensitive |
grep -r 'markdown-toc' . |
recursively search all files in the current directory for the term markdown-toc |
groups |
list all groups for the system |
gunzip |
decompress a file (gunzip doc.pdf.gz). Works the same as gzip -d |
gzip -k |
create a compressed copy of a file (e.g gzip -k doc.pdf) |
gzip -d |
decompress a file (gzip -d doc.pdf.gz). Works the same as gunzip |
head |
print out the first 10 lines of a given file |
head -n 5 app.log |
print out the first 5 lines of a file called app.log |
help |
will open a help file if it exists (for example: brew help, pip3 help) |
history <n> |
shows the previous (n=number) commands |
history | grep 'venv' |
search history for anything with venv in it. Each command will have a number, enter !num to run that command |
hostname |
computers network name |
ifconfig |
show network interfaces (e.g. ip address) |
info |
reports information on a command (info python3, info dirs) |
ip address show |
the modern version of ifconfig shows ip addresses and ranges (linux only) |
ip link show |
shows network interfaces, such as wired connections and Wi-Fi adapters (linux only) |
jobs, bg, fg |
list currently running or suspended jobs, (e.g. if you suspend a process like top using control z, you can see it is stopped using the jobs command). Run fg <n> to resume the job using the number seen in the output of jobs, this will run it it the foreground... use bg 1 to run the process in teh background. |
kill |
kill a process by ID (get ID with ps or top). Note the default signal is -TERM (software termination) |
kill -l |
list the signal types (some of these are also described in man kill), these types can be passed as an option by number, e.g. kill -15 or by name (without the SIG part) e.g. kill -TERM |
kill -KILL <pid> |
force kill a process (kill -9 <pid> also works). You may need to use sudo |
killall |
kill a process by name (e.g. killall -KILL node) |
less |
interactive page through a file... similar to cat but more user friendly as it lets you arrow line by line or spacebar to page down (q to exit). |
ln |
by default creates a hard link (e.g. ln original.txt hardlink.txt) |
ln -s |
creates a soft link (e.g. ln -s original.txt symlink.txt) |
ls |
list current directory |
ls -alh |
lists everything in the current directory with details and human readable numbers |
lsb_release -a |
obtain information specific to your Linux distribution |
man |
read a manual page for a command (e.g. man ls), q to exit from the manual |
mdfind |
search for files or folders |
mdfind -name test -onlyin Documents |
searches for files or folders with the word 'test', in the directory called Documents |
mkdir |
make a directory |
mkdir "Python Books" |
use quotes to identify file names with spaces |
mkdir -p temp/stuff |
will create the temp and stuff directory directories, provided they don't already exist |
mkdir temp/stuff |
will only make the directory stuff if it can find the directory temp |
mv |
move (or rename) a file or directory |
mv Notes Stuff |
essentially renames the Notes directory as stuff (is actually creating a new dir) |
mv file.txt Notes |
moves file.txt into the Notes directory |
nano |
open a file in a very basic text editor |
open |
opens a file or directory (mac only) |
open . |
opens a finder window at the current directory (mac only) |
passwd |
allows you to change your password or another users password if you are admin (e.g. sudo passwd guest) |
popd |
pop directory (returns to the path at the top of the directory stack.) |
pushd |
push directory (saves the current working directory so it can be returned to at any time) |
ps |
show all terminal processes started by the current user |
ps -ax |
show all processes |
ps -ax | grep 'Firefox' |
shoe all processes with 'Firefox' |
pwd |
print working directory |
rm |
remove - BE CAREFUL! |
rm -f |
force remove file without confirmation y/n |
rm -i |
remove with a confirmation |
rm -r |
remove a directory and its contents |
rm -rf |
force remove a directory (hidden files may prevent rmdir from working) |
rmdir |
remove an empty directory |
sed 's/dark/light/' file.txt |
replace the word "dark" with "light" in a file |
sort |
outputs sorted or merged lines of a text file |
sort -n |
outputs sorted or merged lines of a text file numerically |
sort -u |
outputs sorted and removes duplicates (unique values only) |
sort -u | wc -l |
counts the number of unique lines |
su jessica |
switch user to username |
sudo |
super user do - only works if the current user has admin privileges - BE CAREFUL! |
sudo !! |
repeat the last command with sudo |
tail |
print out the last 10 lines of a given file |
tail -n 5 app.log |
print out the last 5 lines of a file called app.log |
tar -cf |
create a tar archive of multiple files (e.g. tar -cf archive.tar file1.txt, file2.txt). Note you can then use gzip to compress the archive to create a archive.tar.gz |
tar -czf |
create a compressed tar archive (same as if you used gzip after creating teh archive) e.g. tar -czf archive.tar.gz file1.txt file2.txt |
tar -xf |
extract files from a tar archive (e.g. tar -xf archive.tar). Note if the archive has also been compressed (with tar -czf or gzip), you don't need to decompress it first, tar -xf will handle it. |
tar -tf |
list filenames in a tar archive (e.g. tar -tf archive.tar) |
top |
much like activity monitor, displays live sorted information on processes (q to quit) |
top -o mem |
sort processes by memory instead of CPU usage |
touch |
makes a file if it does not exist (touch test.txt) or update the last modified timestamp of a file if it does exist |
uniq |
reads a file and outputs removing any duplicate adjacent lines. To remove all duplicates you would sort first (e.g. sort file.txt | uniq). This command is similar to using the -u option with sort but provides more features like -d to only show duplicate lines and -u to only show unique lines or -c to show a count along with each line. |
wc |
output the number of lines, words, and bytes in a given file |
whatis |
gives a one line description of a command (whatis chown) |
which |
shows the path to where something lives (for example: which brew, which python3) |
who |
displays users currently logged in to the system |
whoami |
shows current username |
xargs |
take output of one command and use it as arguments for another command. This is similar to using | but for commands that don't take that kind of input (e.g. cat filesToDelete.txt | xargs rm or find . -size +1M | xargs ls -alh). |
| character | description |
|---|---|
> |
output result to a destination (e.g. date > test.log). Note this action will replace any existing content in the destination file if it exists or create a new file if it doesn't exist. |
>> |
output result to a destination (e.g. date >> test.log). Note this will append the output to an existing file or create a new file if it doesn't exist. |
| |
takes the output of one command and passes as the input of another command (e.g. ls -alh | wc) |
* |
represents any match, e.g. echo *.md will print out the names of all the markdown files in the current directory. |
? |
represents any single character match, e.g. test?.md |
{} |
will iterate through comma separated items (e.g. echo test.{txt,js,css,html} will output test.txt test.js test.css test.html) |
& |
put an ampersand at the end of a command to run it in the background. You can then check that it's running using jobs or bring it to the foreground using fg <n>. |
| key combination | description |
|---|---|
Up Arrow, Down Arrow |
Cycle through your history |
Ctrl + U |
Delete to start of line |
Ctrl + K |
Delete to end of line |
Ctrl + R |
Search history. Repeat Ctrl + R to loop through results |
Ctrl + G |
Cancel the search and restore original line |
Ctrl + W |
Delete previous word |
Ctrl + L |
Clear screen |
Ctrl + D |
Exit Shell |
| combination | description |
|---|---|
Option + Left Click |
Jump cursor to location (shell and vim - might depend on config) |
To temporarily set an environment variable, use the export command in the command line:
export FLASK_APP=run.pyTo permanently set an environment variable, place it in your ~/.bash_profile.
export FLASK_APP=run.py
To see all your current variables:
printenvTo see the value of a specific variable:
echo $FLASK_APPTo change the default shell to Bash:
chsh -s /bin/bash
To change the default shell to Zsh:
chsh -s /bin/zsh
To see a list of all included shells:
cat /etc/shells
ps -ax | grep 'search term' | awk '{print $1}' | xargs kill -9
You can also just run ps then when you find the process, note its PID and run:
sudo kill -9 <PID>
| dir | description |
|---|---|
| /bin | essential user binaries |
| /boot | contains the linux kernel (boot files) |
| /dev | device files (for external devices like hard drives) |
| /etc | system config files |
| /home | home folders (user files) |
| /lib | essential kernel modules and shared libraries |
| /lost+found | recovered files |
| /media | removable media |
| /mnt | temporary mount points |
| /opt | option packages |
| /proc | kernel and process files |
| /root | root home directory |
| /run | application state files |
| /sbin | system binaries |
| /srv | service (server-related) data |
| /sys | virtual file system which allows modification of devices connected to the system |
| /tmp | temporary files (typically cleared on reboot) |
| /usr | user system resources (user binaries and read-only data) |
| /var | variable data files (log files) |