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Midterm 2: Linux & Shell Programming

Terms in this set (27)

pwd
Shows where you are (gives path).
ls
See what files are in current directory.
ls -a
See ALL files in current directory (hidden files).
cd
Go to a directory (i.e. cd Desktop).
mkdir
Create a directory.
rmdir
Remove a directory.
rm
Use to delete files.
rm -r
Use to delete directory.
rm *
Use to delete ALL files in a directory.
touch
Create a file (don't forget file extensions).
man & -help
Use to learn more about commands.
cp
Use the cp command to copy files through the command line. It takes two arguments: The first is the location of the file to be copied, the second is where to copy.
mv
Use the mv command to move files through the command line. We can also use the mv command to rename a file. For example, if we want to rename the file "text" to "new", we can use "mv text new". It takes the two arguments, just like the cp command.
locate
The locate command is used to locate a file in a Linux system, just like the search command in Windows. This command is useful when you don't know where a file is saved or the actual name of the file. Using the -i argument with the command helps to ignore the case (it doesn't matter if it is uppercase or lowercase). So, if you want a file that has the word "hello", it gives the list of all the files in your Linux system containing the word "hello" when you type in "locate -i hello".
echo
The "echo" command helps us move some data, usually text into a file. For example, if you want to create a new text file or add to an already made text file, you just need to type in, "echo hello, my name is alok >> new.txt". You do not need to separate the spaces by using the backward slash here, because we put in two triangular brackets when we finish what we need to write.
cat
Use the cat command to display the contents of a file. It is usually used to easily view programs. Can also be used to display multiple files in one command line.
nano & vi
nano and vi are already installed text editors in the Linux command line. The nano command is a good text editor that denotes keywords with color and can recognize most languages. And vi is simpler than nano. You can create a new file or modify a file using this editor. For example, if you need to make a new file named "check.txt", you can create it by using the command "nano check.txt".
sudo
A widely used command in the Linux command line, sudo stands for "SuperUser Do". So, if you want any command to be done with administrative or root privileges, you can use the sudo command. For example, if you want to edit a file like viz. alsa-base.conf, which needs root permissions, you can use the command - sudo nano alsa-base.conf. You can enter the root command line using the command "sudo bash", then type in your user password. You can also use the command "su" to do this, but you need to set a root password before that. For that, you can use the command "sudo passwd"(not misspelled, it is passwd). Then type in the new root password.
df
Use the df command to see the available disk space in each of the partitions in your system. You can just type in df in the command line and you can see each mounted partition and their used/available space in % and in KBs. If you want it shown in megabytes, you can use the command "df -m".
du
Use du to know the disk usage of a file in your system. If you want to know the disk usage for a particular folder or file in Linux, you can type in the command df and the name of the folder or file. For example, if you want to know the disk space used by the documents folder in Linux, you can use the command "du Documents". You can also use the command "ls -lah" to view the file sizes of all the files in a folder.
tar
Use tar to work with tarballs (or files compressed in a tarball archive) in the Linux command line. It has a long list of uses. It can be used to compress and uncompress different types of tar archives like .tar, .tar.gz, .tar.bz2,etc. It works on the basis of the arguments given to it. For example, "tar -cvf" for creating a .tararchive, -xvf to untar a tar archive, -tvf to list the contents of the archive, etc. Since it is a wide topic, here are some examples of tar commands.
zip & unzip
Use zip to compress files into a zip archive, and unzip to extract files from a zip archive.
uname
Use uname to show the information about the system your Linux distro is running. Using the command "uname -a" prints most of the information about the system. This prints the kernel release date, version, processor type, etc.
apt-get
Use apt to work with packages in the Linux command line. Use apt-get to install packages. This requires root privileges, so use the sudo command with it. For example, if you want to install the text editor jed (as I mentioned earlier), we can type in the command "sudo apt-get install jed".
chmod
Use chmod to make a file executable and to change the permissions granted to it in Linux. Imagine you have a python code named numbers.py in your computer. You'll need to run "python numbers.py" every time you need to run it. Instead of that, when you make it executable, you'll just need to run "numbers.py" in the terminal to run the file. To make a file executable, you can use the command "chmod +x numbers.py" in this case. You can use "chmod 755 numbers.py" to give it root permissions or "sudo chmod +x numbers.py" for root executable.
hostname
Use hostname to know your name in your host or network. Basically, it displays your hostname and IP address. Just typing "hostname" gives the output. Typing in "hostname -I" gives you your IP address in your network.
ping
Use ping to check your connection to a server. Wikipedia says, "Ping is a computer network administration software utility used to test the reachability of a host on an Internet Protocol (IP) network". Simply, when you type in, for example, "ping google.com", it checks if it can connect to the server and come back. It measures this round-trip time and gives you the details about it. The use of this command for simple users like us is to check your internet connection. If it pings the Google server (in this case), you can confirm that your internet connection is active!
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