Create a shortcut to an existing command:
alias gs='git status '
alias ga='git add '
alias gb='git branch '
alias gc='git commit'
alias gd='git diff'
alias gco='git checkout '
alias gf='git fetch '
alias gp='git push '
alias gl='git log --pretty=format:"%h %ad | %s%d [%an]" --graph --date=short'Basically console.log - prints text or expressions passed.
echo $HOME # /home/max
echo $USER # max
echo $((2 + 2)) # 4Basically regexp.
| Pattern | Matches |
|---|---|
* |
Any characters |
g* |
Filenames starting with 'g' |
b*.txt |
Filenames starting with 'b' and ending with '.txt' |
? |
Single character |
data??? |
Filenames starting with 'data' and followed by any 3 characters |
[abc] |
Any character from the set |
[!abc] |
Any character expect from the set |
[:digit:] |
Numeric POSIX class |
[:upper:], [:lower:] |
Uppercase, lowercase |
[[:upper:]]* |
Uppercase character followed by anything |
*[![:lower:]] |
Any filename that does not end with a lowercase letter |
Double quotes "" used to escape everything except $, backslashes and backticks.
Single quotes '' used to escape everything.
The results of the commands be default are sent to the standard output - display. We can redirect it to a file using > to set and >> to append
# overwrite the file with each new call
ls > ls_result
# append new data to the file
ls >> ls_resultTo redirect the standard input from the keyboard to the file, use <
# reverse sort the content of the file line by line
sort -r < ls_resultThe result is displayed on the screen since this is a standard output. We can again redirect it to the file:
sort -r < ls_result > sorted_ls_resultWe can use pipelines | to redirect the standard output of one command to the standard input of another.
ls -l | lessBasically str.match(regexp).
Structure: grep pattern files or some input | grep pattern.
Use this file for testing: unix.txt
UNix
OMGunixOID.
linux Unix which one you choose.
uNix is easy to learn.unix is a multiuser os.Learn unix .unix is a powerful.| Flag | Description | Example | Result |
|---|---|---|---|
| - | - | grep 'unix' unix.txt |
lines 2, 4 |
-v |
inverted match, ! |
grep -v 'unix' unix.txt |
lines 1, 3 |
-i |
case-insensitive | grep -i 'unix' unix.txt |
all 4 lines |
-c |
count of the matches | grep -c 'unix' unix.txt |
2 |
-l |
list of the files with matches | grep -l 'unix' * > result.txt |
result.txt with 'unix.txt' inside |
-w |
word matches | grep -iw 'unix' unix.txt |
lines 1, 3, 4 |
-x |
string matches | grep -ix 'unix' unix.txt |
line 1 |
-o |
display only the matched pattern instead of the whole line | grep -io 'unix' unix.txt |
7 matched words |
^pattern |
line starting with a pattern | grep -i '^unix' unix.txt |
lines 1, 4 |
pattern$ |
line finishing with a pattern | grep -i 'nix$' unix.txt |
line 1 |
Copy files to a remote server via SSH.
# Copy all files in a folder using `key` from `source` to `host:target`
scp -r -i audio_ember_staging.pem ./audio_member [email protected]:/home/ubuntu/audio_emberEach file and directory is assigned access rights for the owner of the file, the members of a group of related users, and everybody else.
Rights can be assigned to read a file, to write a file, and to execute a file.
We can use ls -l filename to see the rights.
ls -l /bin/bash
# -rwxr-xr-x 1 root root 928016 лип 10 19:57 /bin/bashbash is owned by the user root belonging to the group root.
- The superuser can read, write and execute the file
- Members of the group
rootcan read and execute - Everybody else can read and execute
Think of the permission settings as a series of bits:
| Attributes | Binary | Decimal |
|---|---|---|
| rwx rwx rwx | 111 111 111 | 777 |
| rw- rw- rw- | 110 110 110 | 666 |
| rwx --- --- | 111 000 000 | 700 |
Change permissions for a file.
There are two ways to change permissions:
- By setting an octal number
chmod 700 unix.txt- By setting a symbolic representation of changes. The combination of:
u,g,o+,-,=r,w,x
chmod g=rw,u=rwx,o=r unix.txt
chmod u-rwx unix.txt
chmod o+w unix.txtThe common permission sets:
| Decimal | Attributes | What for |
|---|---|---|
755 |
rwxr-xr-x |
Common programs used by everybody |
666 |
rw-rw-rw |
Common files to read and write by everybody |
644 |
rw-r--r-- |
Files that everybody can read but only the owner to modify. |
700, 600 |
rwx------, rw------- |
Private files for the owner only |
chmod can also be used for directory permissions.
rallows the content of the dir to be listed ifxis also set.wallows files within the directory to be created, deleted, or renamed ifxis also set.xallows a directory to be entered (i.e.cd dir).
The common permissions sets for directories:
| Decimal | Attributes | What for |
|---|---|---|
755 |
rwxr-xr-x |
The owner has full rights, everybody else can list and read files but not modify anything |
700 |
rwx------ |
The owner had full rights, everybody else can do nothing - private directory. |
Change permissions for all directories inside a directory:
sudo find /opt/lampp/htdocs -type d -exec chmod 755 {} \;Change permissions for all files inside a directory:
sudo find /opt/lampp/htdocs -type f -exec chmod 644 {} \;Change Owner and Change Group.
chown username file.txt
chgrp groupname file.txtSet User Id. Only affects files.
When the setuid bit is set, an executable runs not with the privileges of the user launching it but with the privileges of the owner.
It is set by adding 4 before the standard octal number:
chmod 4777 myprogor by adding s to the user:
chmod u+s myprogThe file must be executable (x) for this feature to work. If it was executable, s will replaces x. If it wasn't, S will replace x (and nothing will work).
ls -l
# -rwsr--r-- 1 max shareSet Group Id. Affects both files and folders.
When set on a file, an executable file will run with the privileges of the group of the owner instead of the usual group of the user running it.
When set on a foler, makes the group of the files created inside the directory to belong to the group of the directory itself, not to the usual group of the creator. This is very useful for the shared folders: set the common folder group to share and all the files created inside will have this group by default, regardless of the user who creates them.
It is set by adding 2 before the standard octal number:
chmod 2770 myprog # file
chmod 2770 /share # folderor by adding s to the group:
chmod g+s myprog # file
chmod g+s /share # the actual settings for the shared folderResult:
ls -l
# drwxrws--- 2 root shareRemember: the file/folder should also be executable. The capital S will indicate that it is not!
Affects directories.
Makes all the files inside the directory only modifiable by their owners. Typically used for directories writable by all users to make impossible for one of them deleting the files or another.
It is set by adding 1 before the standard octal number:
chmod 1777 /tmpor by adding t to the others' permissions:
chmod o+t /tmpResult:
ls -l
# drwxrwxrwt 20 root rootAgain, capital T will indicate that x is not present for others (and the sticky bit won't work either).
Set File Access Lists. Basically the default permissions for the files inside a directory.
setfacl -d -m g::rwX /<directory> # group
setfacl -d -m o::rX /<directory> # othersFiles cannot be set executable by default!
Put the process to sleep pressing CTRL + Z. Wake up typing bg.
# Run Wireshark for test
sudo wireshark
# Then put it to sleep. And later wake upList all processes for all users:
ps xPipe the output through the grep to find a process you need:
# Assumimg `gnome-system-monitor` is running
ps x | grep monitor
Sends the kill signal to the process.
# Assuming `gnome-system-monitor` is running
ps x | grep monitor
kill 10063List the signals available
kill -lThe standard signal of kill is 15. The most severe is 9 - in this case not the process kills itself but the kernel kills a process.
ps x | grep monitor
kill -9 10063Lists open files for running processes.
Example: find the process running at the specific port:
# Find the process running at port 5000
lsof -i tcp:5000
# Find and kill the process running at port 5000
lsof -i :5000 -t | xargs kill