- etc: system-wide configuration folder (eg. pacman mirrorlist)
- bin: common binary files for applications (eg. ls)
- boot: stores my bootloader
- lib: shared libraries that applications use
- mnt: where external drives are mounted (eg. usbstick)
- opt: manually installed softwares
- proc: information about system processes and resources, each folder is a process’ PID.
- root: volatile storage
- srv: service directory, where service data is stored
- sys: it’s a way to interact with the hardware
- tmp: where files are temporary stored in a session (eg. writing in a libreoffice file)
- usr: user application’s space, where applications will be installed
- var: contains files that are supposed to grow (eg. logs)
- home: where you store your own personal files
| Expression | Description |
|---|---|
#! | locate an executable for the specified script |
!! | executes last command |
!* | executes command with ALL the args passed to the last command |
!^ | executes command with the FIRST arg passed to the last command |
!$ | executes command with the LAST arg passed to the last command |
!?keyword? | execute a command from history for the first pattern match |
!n | execute a command from the nth position in the history |
!<command> | executes a command with the same flags as before |
| Group | Description |
|---|---|
| u | user (owner) |
| g | group |
| o | others |
| a | all |
| Operator | Description |
|---|---|
| + | add permission |
| - | remove permission |
| = | override permission |
| Octal | Description |
|---|---|
| 0 | nothing |
| 1 | execute |
| 2 | write |
| 3 | 1 + 2 (wx) write and execute |
| 4 | read |
| 5 | 4 + 1 (rx) read and execute |
| 6 | 4 + 3 (rw) read and write |
| 7 | 4 + 2 + 1 (rwx) read, write and execute |
| Command | Description |
|---|---|
chmod -R <specifications> <directory> | changing permissions of the contents of a directory recursively |
chmod og=+r | add read permission for the owner and group |
chmod a +rwx file | allow all user to read, write and execute |
chown user1 filename changing ownership of a file to user1
| Command | Description |
|---|---|
su - | invokes a login shell, reseting most environment variables |
su | normal shell |
sudo su | switch to root |
sudo will run a specific command with root level of permission.
sudo !! (last command) for instance
| Command | Description |
|---|---|
cd - | go to the previous working directory |
ls \*D | pathname expansion, returns all files starting with D |
ls exe\* | all files ending with ‘exe’ |
less <file> | view the contents of a file with a pager |
head <file> | first several lines of a file (pass -n <numer-of-lines> to see N number of lines) |
tail <file> | last several lines of a file (pass -n <numer-of-lines> to see N number of lines) |
uname | show informations about the system (-a flag shows ALL info) |
du | summarizes the disk usage of files |
du -sh * | summarizes every file in the current directory |
df | disk space of filesystem |
ps | process status |
ps -C <name> | find the PID of a specific program |
killall <p> | terminates a process |
kill <PID> | terminates a process given the PID |
which | searches for executables specified by the environment variable PATH |
time | time the execution of any program (eg. time node script.js) |
watch -n N | runs a command infinitely each N seconds |
apropos | find a command that I’m unaware of (eg. apropos “list dir”) |
| use in conjuntion with (whatis) command | |
whereis | searches for executables, source files and manual pages |
diff | compares files, and lists their difference |
find | find files in directory (eg. find -name README.md) |
man giteveryday | useful minimul set of commands for everyday git |
curl wttr.in | weather forecast |
curl parrot.live | rainbow parrot |
sha256sum | verify file checksum. (or sha1sum, md5sum depending on the hash) |
curl cheat.sh/<command>/ | get a cheatsheet about a particular command |
Instead of retyping a long list of arguments of a mispelled command,
we can correct whatever typo we made with ^typo^correct
$ dc /tmp
$ ^dc^cd
| Flags | Description |
|---|---|
| -c –create | create a new archive |
| -x –extract | extract files from an archive |
| -t –list | list the contents of an archive |
| -f –file=ARCHIVE | use archive file |
| -v –verbose | list files being processed |
| -z | compress the archive with gzip (faster, but compresses less) |
| -j | compress the archive with bzip2 (slower, but compresses more) |
| –exclude <path> | ignores subfolder |
| Command | Description |
|---|---|
| tar -cf ./archive.tar ./folder | creates an archive from a folder |
| tar -lf ./archive.tar | lists the contents of the archive without extracting it |
| tar -xvf ./archive.tar | extracts the archive |
| tar -cf archive.tar ./folder –exclude “folder/subfolder” | ignores subfolder inside my-folder |
| tar -czvf archive.tar.gz ./folder | creates a gzip archive |
| tar -cjvf archive.tar.bz2 ./folder | creates a bzip2 archive |
| gunzip <filename> | un-compresses files compressed by gzip |
| gzcat <filename> | look at a gzipped file without having to gunzip it |
| gzip <filename> | compresses a file to gzip format |
| bzip2 <filename> | compresses a file to bzip2 format |
| Flag | Description |
|---|---|
--list-keys | list all keys keyring |
--import <key-path> | Add a pubkey into keyring |
--delete-key <fingerprint> | Del key in keyring |
$ gpg --keyserver <server> --recv-keys <hex>Where <server> can be “pgp.mit.edu” for instance.
Having the receiver’s pkey:
$ gpg --output doc.gpg --encrypt --recipient mail@recipient doc$ gpg --output doc --decrypt doc.gg-c is for symmetric encryption (single pkey for encrypting/decrypting).
$ gpg -c --no-sym-key-cache --cipher-algo AES256 <file>We can use shell expansion to:
- rename and backup operations
- pattern matching
- match any string
- The
*is a greedy operator that matches any string, incuding the null string.
$ echo file* returns file.log file.tex file.txt file.exe
$ echo *.tex returns file.tex
- The
?matches a single character.
$ echo file?.txt returns file1.txt file2.txt file3.txt ...
- The
^character represents not.[abc]means either a, b or c[^abc]any character that is not a, b or c
To backup settings.conf to settings.conf.bak:
cp settings.conf{,.bak}
To revert the file from settings.conf.bak to settings.conf:
mv settings.conf{.bak,}
Other uses:
echo foo{1,2,3}.txt outputs foo1.txt, foo2.txt, foo3.txt
echo file-{a..b}.txt outputs file-a.txt file-b.txt file-c.txt file-d.txt
mv program.{c,exe} bin/
The output from a command normally intended for stdout can be easily diverted to a file.
$ who > users
$ cat users
nexi tty01 Oct 22 08:58
ai tty02 Oct 22 13:58The > operator will always override the contents of the file.
We can use the >> operator to append the output in a file with existing info:
$ echo lorem ipsum >> users
$ cat users
nexi tty01 Oct 22 08:58
ai tty02 Oct 22 13:58
lorem ipsumCommands that receive input from stdin can have their input redirected from a file.
$ wc -l < users
3A “here document” redirects input into an interactive shell script or program.
command << EOF
document
EOFThe >> command is an instruction to read input until it finds a line containing the delimeted (EOF in this case)
$ wc -l <<EOF
lorem ipsum
dolor sit
amet
EOF
3&(Ampersand Operator)run one or more jobs in the background,
EXAMPLE: ping www.google.com & apt-get update & apt-get upgrade &
Ctrl-zpauses the jobjobsprints all the jobs
;(Semi-colon operator)run several commands at once sequentially, disregarding the exit status of the preceding command
EXAMPLE: apt-get update ; apt-get upgrade ; mkdir test
&&(AND operator)executes a command IF the exit status of the preceding command is 0
EXAMPLE: ping www.google.com && links www.google.com (checking the connection before using links command)
||(OR operator)much like an ‘else’ statement, allows to execute the second command only if the execution of the first fails (i.e., the exit status is 1)
EXAMPLE: apt-get update || links www.google.com
!(NOT operator)much like an ‘except’ statement, this command will execute all except the condition provided
EXAMPLE: rm -r !(*.html) removes all files in a folder except .html files
|(PIPE operator)passes the output of the first command to the second one
EXAMPLE: ls -l | less
{}(Command Combination operator)combine two or more commands
[ -d Folder] || { echo creating Folder; mkdir Folder; } && echo Folder exists.
grep(Globally search for a Regular Expression and Print) for searching stuff in files, or any STDOUT (eg. ‘ls’ command)EXAMPLE:
ls | grep "\.exe$"sed(stream editor) for substitituing, deleting or filtering text on a streamEXAMPLE:
sed 's/regexp/replacement/g' file > output-r will extend the Regex portability (POSIX)
xargs(command args) pass any command to it and it will execute it on a stream.EXAMPLE:
find | grep "\.exe$" | xargs ls -lh
| keybinding | description |
|---|---|
ctrl-u | delete from cursor position to beginning of line |
ctrl-k | delete from cursor position to end of line |
ctrl-l | clear screen |
ctrl-w | delete last word |
ctrl-r | search through command history |
alt-. | cycles through last arguments |
alt-* | expands glob |
Steps to free disk space on your Linux machine:
- Check directories disk space:
cd / && sudo du -h --max-depth=1 - Delete pacman cache:
sudo paccache -rkeep at least 3 cachessudo paccache -rk 1keep only 1 pkg cache