Command-line interface(CLI) is a way that allows users to interact with computer programs through commands. A user issues commands to a program which gets interpreted by a command-line interpreter. Most operating system implements CLI in the form of shells that are used for interactive access of the various services or functions of the operating system. CLI has its own benefits over a graphical user interface(GUI). The command-line interface is more efficient than a GUI. A program can be accessed through CLI, which is not accessible on GUI. So in this article we are going to discuss some important commands that are used in Linux/Unix terminal frequently.
File commands –
| COMMANDS | DESCRIPTION |
|---|
ls | List files and directories under the current working directory |
pwd | Show the path of the current working directory |
mkdir dir(s) | Make a directory with name dir |
cd dir | Change directory to dir |
cd | Change the current directory to home directory |
rm -r dir(s) | Remove or delete the directory dir |
rm -rf dir(s) | Delete the directory dir forcefully |
touch file(s) | Create a file |
rm file(s) | Delete the file |
rm -f file(s) | Delete the file forcefully |
cat >file | Place the standard input into the file |
cp file1 file2 | Copy the content of file1 to file2 |
cp -r dir1 dir2 | Copy the directory dir1 to dir2 |
mv file_or_directory dir | Move a file or directory to directory dir |
System info commands –
| COMMANDS | DESCRIPTION |
|---|
date | Show the current date and time |
cal | Show the month’s calendar |
uptime | Show the current uptime(total time of the current session since you log in) |
w | Display who is online |
whoami | Display who are you logged in as |
uname -a | Display the kernel information |
finger user_name | Display about the user |
man command | Display the manual for the given command |
df | Show the disk usage and other related information |
du | Show directory space usage |
free | Show the physical memory and swap usage |
cat /proc/cpuinfo | Display Cpu information |
cat /proc/meminfo | Display Memory information |
File/directory searching commands –
| COMMANDS | DESCRIPTION |
|---|
grep pattern | Search for patterns in a file |
grep -r pattern dir | Search recursively for a pattern in dir |
command | grep pattern | Search pattern in the output of a command |
locate file | Display the path of the file with other file having a similar name |
find .-name filename | Searches in the current directory and below it for files and directories with the names starting with filename |
pgrep pattern | Searches for all the named processes, that matches with the pattern and by default, it returns their process ID |
Commands used in process management –
| COMMANDS | DESCRIPTION |
|---|
ps | Display the current working process |
top | Display the all running process with resource usage |
kill pid | Kill the process with given process ID |
killall -9 name | If more than one process runs with that name, all of them will be killed |
pkill pattern | Kill the multiple process matches with pattern |
bg | Resume a stopped job in the background |
fg | Resume a stopped job in the foreground |
Detailed use of process management commands with examples are given in a separate article. You should read process management in Linux/Unix.
File permission commands –
chmod octal file -Change the permission of file to octal, which can be found separately for user, group, world by adding, 4-read(r), 2-write(w), 1-execute(x). For detailed use of file permission commands, you should read this article file ownership and permissions in Linux/Unix.
Network commands –
| COMMANDS | DESCRIPTION |
|---|
ping host | Ping the given host and output the result |
whois domain | Display the information about domain and its owner |
dig domain | Display DNS information for a domain |
dig -x host | Reverse lookup host |
wget file | Download file |
wget -c file | Continue a stopped download |
Compression commands –
| COMMANDS | DESCRIPTION |
|---|
tar cf file.tar file(s) | Create tar named file.tar containing file |
tar xf file.tar | Extract the files from file.tar |
tar czf file.tar.gz file(s) | Create a tar with gzip compression |
tar xzf file.tar.gz | Extract a tar using Gzip |
tar cjf file.tar.bz2 file(s) | Create tar with Bzip2 compression |
tar xjf file.tar.bz2 | Extract a tar using Bzip2 |
gzip file | Compress file and rename it to file.gz |
gzip -d file.gz | Decompress file.gz back to file |
Shortcuts used in Linux/Unix terminal –
| COMMANDS | DESCRIPTION |
|---|
ctrl+c | Halts the current command |
ctrl+z | Suspend the current command and can be resumed using fg or bg |
ctrl+d | Logout the current session |
ctrl+w | Erases one word in the line |
ctrl+u | Erases the whole line |
ctrl+r | Type to bring up whole command or reverse search |
!! | Repeat the last command |
exit | Logout the current session |