mkdir → to make a new directory
ls → to print list of all dirctories and files
clear → to clear terminal
whoami → to display the current user
pwd → display the current working directory
cd → to change directory
touch filename.txt → create a empty text file
touch file{1..5}.txt → create 5 empty file
cat > filename.txt → add content to file from terminal
cat filename.txt → print content of file
cat file{1..2}.txt → print content of file1 to file2
cat >> file1.txt → to update content of file
cp file1.txt file2.txt → copy content of file1 into file2
mv file3.txt f3.txt → rename file3 as f3
wc -l file1.txt → print count of lines in file
wc -w file1.txt → print count of words in file
wc -m file1.txt → print count of character in file
cmp file4.txt file5.txt → compare two file byte by byte and tell its identical or not
comm file4.txt file5.txt → gives what is comman in file4 and file5 (also used to find unique)
diff file4.txt file5.txt → give difference between file4 and file5
sort f{1..2}.txt → sort content of f1.txt and f2.txt (alphabetically)
cat f1.txt f2.txt > f3.txt → merge two files f1.txt and f2.txt and copy in to f3.txt
sort f3.txt | uniq -u → remove all dublicates from f3.txt and print (doesn’t affect the original file).
tr a-z A-Z < f1.txt → translate lower case to upper case (doesn’t affect the original file).
sed ‘s/[0-9]*//g’ < f1.txt → remove numeric values from file.
head f3.txt → print first 10 lines from file
tail f3.txt → print last 10 lines from file
more f3.txt → print all things *
less f3.txt → print all things *
grep -w linux < file9.txt → it gives all lines containing linux word (grep linux file9.txt)
grep -n linux < file9.txt → it gives line number with line containing linux word
grep -a --count linux < file9.txt → it gives count of line containing linux word
grep ‘+linux*’ file9.txt → gives the lines which starts from linux word
grep ‘os$’ file9.txt → gives lines which ends with os word
ls -l → gives what permissions files have
ls -l filename→ gives what permissions files have
ls -ld → gives directory permissions
history > workdone.txt → history give all the commands that we just write we can store it text file
w → gives info about all users
Permissions
rwx rwx rwx
user group other
Note that “r” is for read, “w” is for write, and “x” is for execute
chmod ugo+rwx foldername → to give read, write, and execute to everyone.
chmod a=r foldername → to give only read permission for everyone.
- The first character will almost always be either a ‘-‘, which means it’s a file, or a ‘d’, which means it’s a directory.
- The next nine characters (rw-r–r–) show the security;
- The next column shows the owner of the file. In this case it is me, my userID is “aditya314”.
- The next column shows the group owner of the file. In my case I want to give the “aditya314” group of people special access to these files.
- The next column shows the size of the file in bytes.
- The next column shows the date and time the file was last modified.
- And, of course, the final column gives the filename.
chmod 755 file.txt → to change permissions of file
chmod 555 ce → change permission of directory
new permission will be -rwxr-xr-x
id → gives information about current user and groups and other info
$HOME → gives path of home.
$PATH → also give path
sudo su → become root user
head -5 file.txt → print first five lines
tail -2 file.txt → print last two lines
rm file.txt → remove file
rm -r directory_name → remove dirctory
sudo adduser username → adds a new user
sudo addgroup g1 → adds new group
sudo groupadd -g 10000 groupname → create group
cat /etc/group → display all the groups
sudo usermod -aG groupname username → add user to a group
sudo chown username filename → to change username
sudo chown username:groupname filename`→ change group name
sudo chgrp groupname filename → change groupname
sudo chgr groupname directoryname → change groupname
umask → display current value of shells mask
umask 531 → set umask
top → display all processes
ps → give all process associated with current user
ps aux → list down all the processes associated with their terminal and states
ps l →
ps lx →
kill -l → display all names and number of available signal
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