Linux Basics Exercises

1. List the user names of all logged-in users on the current system, note: The same user logged in multiple times, only one time is displayed

[[email protected] ~]# whoroot     tty1         2018-06-08 12:24root     pts/0        2018-06-08 10:58 (192.168.6.88)[[email protected] ~]# who | cut -d‘ ‘ -f1 | uniq or [[email protected] ~]# who | cut -d‘ ‘ -f1 | sort -uroot

2. Remove information about the user who last logged on to the current system

[[email protected] ~]# last | head -1root     pts/1        192.168.6.88      Fri Jun  8 12:40   still logged in

3. Remove the shell that is the user's default shell on the current system.

[[email protected] ~]# cut -d: -f7 /etc/passwd | sort | uniq -c | sort -n | tail -1 | cut -d‘ ‘ -f7/bin/bash

4. Change the value of the third field in the/etc/passwd to the top 10 user and save the information to the/tmp/maxusers.txt file.

[[email protected] ~]# sort -n -t: -k3 /etc/passwd | tail | tr ‘a-z‘ ‘A-Z‘ > /tmp/maxusers.txt[[email protected] ~]# cat /tmp/maxusers.txtBASH:X:4008:4008::/HOME/BASH:/BIN/BASHBASHER:X:4009:4009::/HOME/BASHER:/BIN/BASHTESTBASH:X:4010:4010::/HOME/TESTBASH:/BIN/BASHNOLOGIN:X:4011:4011::/HOME/NOLOGIN:/SBIN/NOLOGINUSER5:X:4012:4012::/HOME/USER5:/BIN/BASHUSER6:X:4013:4013::/HOME/USER6:/BIN/BASHUSER7:X:4014:4014::/HOME/USER7:/BIN/BASHHADOOP:X:4015:4015::/HOME/HADOOP:/BIN/BASHFEDORA:X:4016:4016::/HOME/FEDORA:/BIN/BASHCENTOS:X:4017:4017::/HOME/CENTOS:/BIN/BASH

5. Remove the IP address of the current host and tip: Slice the results of the ifconfig command

[[email protected] ~]# ifconfig eno16777736 | grep "inet " | cut -d‘ ‘ -f10192.168.6.89

6. List the file names of all files ending with. conf in the/etc directory and convert their names to uppercase and save them to the/tmp/etc.conf file

[[email protected] ~]# ls -R /etc | grep ".conf$" | tr ‘a-z‘ ‘A-Z‘ > /tmp/etc.conf

7. Displays the total number of subdirectories or files under the/var directory

Is this question ambiguous? So give two answers:

Limited to this layer directory under the/var directory:

[[email protected] ~]# find /var | grep "^/var\(/[^/]*\)\{2\}$" | wc -l81

is limited to subdirectories of this level directory under the/var directory:

[[email protected] ~]# find /var | grep "^/var/[^/]*$" | wc -l21or [[email protected] ~]# ls -A /var | wc -l

8. Remove the names of the 10 groups with the smallest number of third fields in the/etc/group file

[[email protected] ~]# sort -n -t: -k3 /etc/group | head | cut -d: -f1rootbindaemonsysadmttydisklpmemkmem

9. Save the contents of the/etc/fstab and/etc/issue files to a/tmp/etc.test file after merging them into the same content

[[email protected] ~]# cat /etc/fstab /etc/issue > /tmp/etc.test

　
　

Linux Basics Exercises