Common Unix/Linux & g++ Commands
Tips and resources that are useful for the course.
What is this?
This page can be used as a reference for the basics of the COSC 102 course. It is not meant to be a complete reference, but rather a quick reference for the most common things you will need to know.
This page is aimed at Unix/Linux computers. If you are using Windows, it's more or less the same, but some of the syntax is slightly different like how Windows uses \ instead of / for paths, and the file system structure is different. (e.g. C:\ is the root directory for Windows, but / is the root directory for Unix/Linux. C:\Desktop is the Desktop folder for Windows, but /home/<username>/Desktop is the Desktop folder for Unix/Linux.)
g++ - The C++ Compiler
Compiling
Whenever going to submit your code for an assignment, ALWAYS make sure it compiles and behaves (as intended) before doing so -- ON THE LAB MACHINES. Compilers work different across computers, so even if it compiled on your computer, it doesn't necessarily compile or behave the same way on the lab machines. The TA's grade using the lab machines, so if your code doesn't compile or work correctly there, you will not get credit for the assignment.
g++- Stands for GNU C++ Compiler. This command is used to compile C++ programs. It is the default compiler for C++ programs on Unix/Linux systems. It is also the compiler we will be using in this course.
There are many ways to use the g++ command, but the most common way is to use the following syntax:
g++ -std=c++11 -o <binary> <source>.cpp
| binary | source |
|---|---|
| The name of the binary (final executable) you want to create | The name of the source file (your code) you want to compile |
example
g++ -std=c++11 -o foo lab1.cpp
Running
This will compile the lab1.cpp file and create a binary called foo that you can run with
./foo
Notice foo is just a random name. You can name the executable whatever you want, since the g++ command will create the binary you specify. Usually though you want to name it something that makes sense, like the name of the program you're writing e.g. lab1 or lab2 etc.
We use ./ to tell the computer that we want to run a binary in the current directory. If you want to run a binary in a different directory, you can use the full path to the binary without the .
Later in the course, you may be required to compile programs with extra flags that are specific to the lab. These flags will be provided to you in the lab instructions, but it's paramount that you compile with these flags when required. Often times they affect the way your program runs, and if you don't compile with the correct flags, your program may not run correctly, or it may not compile at all, which will net you a 0 on the lab without chance for appeal.
Logging into the lab machines
ssh - Stands for Secure Shell. This command allows you to log into a remote server. It is used to log into the lab machines.
ssh Syntax
| NetID | Number |
|---|---|
| Your UTK NetID | Any number [0,30] |
# syntax
ssh <netid>@tesla<number>.eecs.utk.edu
# example
ssh bricker1@hydra12.eecs.utk.edu
tesla and hydra are interchangeable. You can use either one to log into the lab machines. Also, any progress on the lab machines is transferred to the others. In other words, it doesn't matter what number or machine you use, you can always access your files from any other machine.
Copying to and from the lab machines (scp)
Here is a full ssh and scp tutorial.
scp - Stands for Secure Copy. This command allows you to copy files from a remote server to your local computer or vice versa.
scp Syntax
| File | NetID | Number | Destination |
|---|---|---|---|
| The path to the file you want to copy | Your UTK NetID | Any number [0,30] | The path to the location you want the file copied |
From your computer to the lab computers
# syntax
scp <file> <netid>@tesla<number>.eecs.utk.edu:<destination>
# example (Unix/Linux)
scp ~/Documents/cs102/hello.cpp bricker1@hydra2.eecs.utk.edu:~/cs102/labs/lab1/
# example (Windows)
scp C:\Users\bricker1\Documents\cs102\hello.cpp bricker1@hydra2.eecs.utk.edu:~/cs102/labs/lab1/
From the lab computers to your computer
# syntax
scp <netid>@tesla<number>.eecs.utk.edu:<file> <destination>
# example (Unix/Linux)
scp bricker1@hydra2.eecs.utk.edu:~/cs102/labs/lab1/hello.cpp ~/Downloads/
# example (Windows)
scp bricker1@hydra2.eecs.utk.edu:~/cs102/labs/lab1/hello.cpp C:\Users\bricker1\Downloads\
Common SCP FAQs/Errors
If you're copying a file from your computer to the lab computers, you need to make sure one of the following is true:
- You are in the same directory as the file you want to copy
- You provide the full path of the file you want to copy
If you aren't in the same directory as the file you want to copy, then you can use cd to navigate to the directory that contains the file you want to copy. Or you can provide the full path to the file you want to copy. (e.g. scp ~/Desktop/file.txt as opposed to scp file.txt)
scp ~/Desktop/file.txt <netid>@tesla<number>.eecs.utk.edu:<destination>
# as opposed to
scp file.txt <netid>@tesla<number>.eecs.utk.edu:<destination>
If you are in the same directory, then the path you use for the file you want to copy is just the name of the file.
If you're copying a file from the lab computers to your computer, then <file> & <destination> will always be the full path to the file you want to copy. (e.g. ~/cosc102/labs/lab1.cpp for <file>). You can however copy a file to your current directory by using . as the destination.
scp <netid>@tesla<number>.eecs.utk.edu:~/cosc102/labs/lab1.cpp .
Other commands you should know
List files in a directory
ls- Stands for List. This command is used to list the contents of a directory. It is often used to see what files are in a directory, or to see if a file exists in a directory. There are multiple flags you can use withlsthat alter the output
ls -a # lists hidden files/directories (ones that start with a . character)
ls -l # a more detailed list of the current directory. It shows things like file mod times, permissions, and more
ls <directory/file> # lists the contents of a specific directory/lists whether a file exists in the current directory, respectively
Change directory
cd- Stands for Change Directory. This command is used to change the current directory. It is often used to navigate to a specific directory, or to navigate back to your home directory.
cd <directory> # changes the current directory to the directory specified
cd .. # changes the current directory to the parent directory of the current directory (moves back one)
cd ~ # changes the current directory to your home directory
Print current directory path
pwd- Stands for Print Working Directory. This command is used to print the current directory. It is often used to see what directory you are currently in.
pwd
Make a new directory
mkdir- Stands for Make Directory. This command is used to create a new directory.
mkdir <new-directory-name>
Copy a file or directory
cp- Stands for Copy. This command is used to copy a file or directory.
cp <source> <destination>
cp -r <source-directory> <destination-directory>
Move/rename a file
mv- Stands for Move. This command is used to move a file to a different location. You can also use it to rename a file.
mv <source> <destination> # moves source to destination or renames source to destination
Remove a file or directory
rm- Stands for Remove. This command is used to remove files and directories.
rm <file> # removes a file
rm -r <directory> # removes a directory and all of its contents
Create a new file
touch- This command is used to create a new file.
touch <new-file-name>
Print the contents of a file
cat- Stands for Concatenate. This command is used to print the contents of a file to the terminal.
cat <file>
Tips & Important Notes
I'm just gonna throw out a bunch of small bits of info here that I see students struggle with often.
- Instead of typing
/home/netid/in SCP/SSH, use~. This is basically shorthand for that path. So/home/netidis the same thing as~. - When you're in a directory, you can use
..to go back one directory. So if you're in/home/netid/cosc102/labs, you can usecd ..to go back to/home/netid/cosc102