Redirections

• Redirect the output of the ls command to the /tmp/lista-<username>.txt file, where the <username> is your login name!

feri@columbo:~$ ls >/tmp/lista-feri.txt

feri@columbo:~$ ls >/tmp/lista-${USER}.txt

• Concatenate all files in the /etc directory which have .conf extension to one big file in named /tmp/lista-<username>.txt! What happened its previous content?

feri@columbo:~$ cat /etc/*.conf >/tmp/lista-feri.txt

feri@columbo:~$ cat /etc/*.conf >/tmp/lista-${USER}.txt

• Append the current date and time to the end of the /tmp/lista-<username>.txt!

feri@columbo:~$ date >>/tmp/lista-feri.txt

feri@columbo:~$ date >>/tmp/lista-${USER}.txt

• Create this new directory: /tmp! Redirect the error message into the hiba.txt!

feri@columbo:~$ mkdir /tmp 2>hiba.txt

Filters

• Show the content of /etc/passwd page by page!

feri@columbo:~$ cat /etc/passwd | more

feri@columbo:~$ cat /etc/passwd | less

feri@columbo:~$ cat /etc/passwd | most

• Show all lines from the /etc/passwd which contain the sh string!

feri@columbo:~$ cat /etc/passwd | grep sh

• Show all lines from the /etc/passwd which don't contain the sh string!

feri@columbo:~$ cat /etc/passwd | grep -v sh

• Show all lines from the /etc/passwd which first character is s!

feri@columbo:~$ cat /etc/passwd | grep ^r

• Show all lines from the /etc/passwd which last part is false!

feri@columbo:~$ cat /etc/passwd | grep false$

• Show all lines from the /etc/passwd which login name starts with f!

feri@columbo:~$ cat /etc/passwd | grep ^f

• Show all lines from the /etc/passwd which login name dont't contain feri!

feri@columbo:~$ cat /etc/passwd | cut -d: -f1 | grep -v feri

• Show all lines from the /etc/passwd which contains in the login name field the root user!

feri@columbo:~$ cat /etc/passwd | grep ^root:

• how many users are in that system whose name start with a vocal letter? Do not make difference between uppercase and lowercase letters!

feri@columbo:~$ cat /etc/passwd | grep -i ^[aeiou]

• How many user are there without a bash shell?

feri@columbo:~$ cat /etc/passwd | grep -v /bin/bash$

• Show all lines from /etc/bash.bashrc which aren't comments and aren't empty! (Comments start with #, empty lines are ^$)!

feri@columbo:~$ cat /etc/bash.bashrc | grep -v ^$ | grep -v ^'#'

• Write the output of the previous task to your home directory into the bash.txt file!

feri@columbo:~$ cat /etc/bash.bashrc | grep -v ^$ | grep -v ^'#' >bash.txt

• How many folders are in the /etc which group right are: r-x?

feri@columbo:~$ ls -l /etc | cut -c 5-7 | grep r-x | wc -l

• Show the login history of the root (in this month)!

feri@columbo:~$ last | grep root

• Is the root user logged in the system?

feri@columbo:~$ w | grep ^root

• How many different shell exists in the system?

feri@columbo:~$ cat /etc/passwd | cut -d: -f7 | sort | uniq

• Show the name of all logged users! If somebody logged in more than once, only one name should be listed!

feri@columbo:~$ w -h | cut -d' ' -f1 | sort | uniq

• Which users has logged in this month except the reboot user?

feri@columbo:~$ last | grep -v ^$ | grep -v 'wtmp begins' | cut -d' ' -f1 | sort | uniq | grep -v reboot

• List the name of all users in a sorted list!

feri@columbo:~$ cat /etc/passwd | cut -d: -f1 | sort

• How many lines start in the /etc/passwd with f?

feri@columbo:~$ cat /etc/passwd | grep ^f | wc -l

• Show the first three lines of the /etc/passwd file!

feri@columbo:~$ cat /etc/passwd | head -3

• Show the last seven lines of the /etc/passwd file!

feri@columbo:~$ cat /etc/passwd | tail -7

• Show the first twelwe and the last twelve names from the list of users! Try to solve this with one line!

feri@columbo:~$ cat /etc/passwd | head -1 ; cat /etc/passwd | tail -12

• Which user logged in first in this month?

feri@columbo:~$ last | tail -3 | head -1

• How many lines does have the /etc/passwd file?

feri@columbo:~$ cat /etc/passwd | wc -l

• How many characters are in the /etc/passwd file last 8 lines?

feri@columbo:~$ cat /etc/passwd | tail -8 | wc -c

• How many characters are in the directory of the /etc folder?

feri@columbo:~$ ls /etc | wc -c

• How many times has the root logged in this month?

feri@columbo:~$ last | grep ^root | wc -l

• show the sorted content of /etc/passwd!

feri@columbo:~$ cat /etc/passwd | sort

• Show all UIDs from the /etc/passwd in reverse order!

feri@columbo:~$ cat /etc/passwd | cut -d: -f3 | sort -r -n

• Which is the biggest UID in the /etc/passwd file?

feri@columbo:~$ cat /etc/passwd | cut -d: -f3 | sort | head -1

• Show the first 15 lines in ascending order from the /etc/passwd!

feri@columbo:~$ cat /etc/passwd | sort | head -15

• How many lines and how many characters are in the output of the previous command?

feri@columbo:~$ cat /etc/passwd | sort | head -15 | wc -l -c

• Show all real names from the /etc/passwd file and replace all spaces to a _ character!

feri@columbo:~$ cat /etc/passwd | cut -d: -f5 | tr ' ' '_'

• Delete all j character from the list of users!

feri@columbo:~$ cat /etc/passwd | tr -d 'j'