As I mentioned on the previous page, Unix has multiple purposes and can execute various tasks. Evidently, this is what makes it such a reliable resource for Mac users everywhere. One useful feature is that it can perform different functions involving files. You can use Unix to copy, move, and delete files from your computer. Of course there are so many commands that you can use, but for the purpose of this website, I will only be discussing a handful of them. This page is an introduction to the type of Unix commands that are used to manipulate files. Such commands include ls, lpr, chmod, cp and many more. With these commands, you can change file permissions, lists content in your folders, zip files, and perform other unique tasks. In case you are not familiar with file permissions and access levels of files, don't worry. This will all be discussed in the pages of this section.

You may want to look at other pages for further clarification, as they specifically elaborate what these commands do and how to use them at the right moment. Learning how to use these commands is vital to mastering Unix and all it has to offer. In this section, you will learn how to work with files using Unix commands. After taking a look at these commands and their functions, you will have a better idea of how they should be used. Ready to dive in?

If you're familiar with FTP software, you've probably had experience with changing file or directory permissions. Read, write, and execute are access levels that must be taken into consideration when working with files. In fact, there are numbers associated with the access levels. 4 corresponds to the read access level, 2 corresponds to write, and 1 corresponds to execute. The numbers all add up to 7, which indicates full access to a file or directory. There are three categories that you must determine the access levels for. These categories are comprised of the user, group, and everyone else. Now let's take a look at the syntax for the chmod commands:

• chmod filename mode

To better understand the syntax, let's take a look at an applied example:

• chmod index.html 644

I'll explain the reason for the numbers in the mode. Let's examine the first digit of 644. The first digit signifies the access level of the first category, the user. As I mentioned before, 4 coincides with read, 2 coincides with write, and 1 coincides with execute. If you add 4 and 2 together, the outcome is obviously 6. This indicates that the user has access levels of read and write. Now let's look at the second digit, the next category. This category represents the group. Notice that the group category has 4 as a digit. This shows that the group category has an access level of read. The last category, everyone else, has the same access level because it too has a digit of 4. Basically, the chmod command sets the permissions for both files and directories alike.

Ever wanted a file in more than one directory? Well, the cp command will most definitely get the job done for you. This command enables you to copy files. You might be wondering if the cp command is useful. May I kindly state that it can be useful, especially if you accidentally delete a file. With this command, you can have a copy of the same file saved somewhere else or even in the same directory. There are two of many ways in which you can use the cp command. One way is its default function, which is copying files from one location to the next. Another way is using the * wildcard followed by an extension to copy all files with the same extension to a designated directory.

Here are examples of how to use this command in both ways:

• cp filename newDirectory
• cp *fileExtension newDirectory

Now apply these commands in a real scenario like the one shown below

• cp my.txt my_folder
• cp *.txt my_folder

It may not seem like an important task, but comparing files can be advantageous to you. Often times, you may desire to see where your files may differ. One command that can help you do that is the diff command. To put simply, this command allows you to compare files and view their differences. Specifically, it displays both files and the lines that are distinct to their respective files. In other words, you will only be able to see the differences rather than the similarities. This can also be done with directories, especially since they carry multiple items and content inside. While this command works interchangeably with directories, we will focus on how it can affect files for the sake of this section of the website.

The syntax for the diff command can be found below:

• diff filename1 filename2

Here's an applied example:

• diff my.txt this.txt

On the computer, you've probably zipped files before. You can simply do this in multiple steps by holding the shift button, right-clicking the desired file or folder, going to the option 'Send To', and selecting the sub-option 'Compressed(zip folder)'. This sounds like it can be a hassle, but there is an easier way to zip files using Unix. This action involves a command known as gzip. You can guess by a part of the name that this command deals with compressing files, or zipping it. It is convenient to compress files due to the fact that the end result produces a smaller size file. Logically speaking, the smaller the size of the file, the less space it takes up on your computer. As a result, this command can be very beneficial in the long run because you'll have more space to work with after using it on multiple files. More importantly, gzip is said to give the highest compression rate and gives its files the ending .gz. Here is the proper syntax for the gzip command: gzip filename.

Commands Relating to gzip

There are a few commands that relate to the gzip command. One of them is known as gunzip. This is basically the opposite of the gzip command in the sense that it uncompresses any files that were compressed by gzip. Another command is known as gzcat, which allows you to view zipped files without unzipping or uncompressing them. By using this command with the lpr command, you can even print out the file. Below is the proper syntax for each scenario and command that was discussed:

• gunzip filename
• gzcat filename
• gzcat filename | lpr

One great feature about Unix that even I did not know about until now is the fact that you can print your files straight from the terminal. The command that we will discuss to accomplish this is lpr. With this command, you can print anything you desire. There's also options that you may want to specify when attempting to print a file from your terminal. For instance, you can print double-sided documents in Unix. In order to do this, you must input lpr -Pvalkyr-. Also, you must use the -P option to specify the printer that you want to use if you are not going to use your default printer. Other commands, such as lpq and lprm, deviate from the main function of lpr, but are still separate commands nevertheless.

The lpq command allows you to check out the printer queue. With this information, you can get the number necessary to halt the printing process or view the number of files being printed before yours.

The lprm command allows you to delete a file from the printer queue. While using this command, you must use the job number from the printer queue to remove that file. You may also have to specify the name of the printer if it is not your default printer that you are using.

The ls command is a very useful tool in the sense that it tells you what files you have in your working directory. In other words, it gives you a list of the items. One advice I would give you to remember the ls command is to think about the word list and remember that the letters ls are found in that word. This sounds a bit cheesy, but it works. Also, you can use this command to confirm that you have a certain file in your directory. As the saying goes, better safe than sorry.

There are other commands that branch off the ls command, such as ls-l and ls-a. The ls-l command lists out all the files in long format. This command gives other useful information as well, such as the last time the files were modified and the exact size of them. The ls-a command is essential if you want to list the hidden files, which are usually the ones that start with a dot in their name.

By using the ls command, you will be able to organize yourself and keep track of all files in your directories. After all, things can get out of hand if you lose track of everything. Let's say you misplaced a file somewhere on your computer but don't know where to locate it. The ls command can list all files and content of the current working directory, which enables you to view everything that you have. This can help you locate a file, but it may take awhile because you have to insert this command for every directory until you find the lost file. My advice to you is to use the command ff to locate a missing file. It will save you ample time to do other important things and make your life easier. Just remember the file name in order to find it. Other than that, the ls command will list everything for you.

It's obvious that you may want to move certain files around on your computer on certain occasions. Let's say you had a file saved in the wrong directory and wanted to move it in your intended one. This command serves its function in this type of scenario. As the name suggests, the mv command moves the file around but does one of two things: transfer it to another directory or give it a different name. In other words, it can also be used as a renaming tool. When you think of the mv command, think of the word move. This may help in case you forget the command.

Below is the proper syntax for the command to utilize its effectiveness:

• mv filename1 filename2
• mv filename /destination/directory

• mv my.txt this.txt
• mv this.txt /Desktop/my_folder
• ls

Filename1 is referred to as the file's original name. Filename2 is the name you desire to change your file to. If you want to retain the same name and just move the file, set filename1 and filename2 identical to each other. The bottom command is used to move the file to a different location. Use the command ls to confirm that you have the file in the right place.

You will most definitely find yourself in a situation where you amy have to delete some files on your computer. This scenario can occur if you either have files that are no longer important or if you need to make room for files that are more important. Nevertheless, it is a significant decision to make, especially with the command rm. This command not only deletes the file, but it also permanently discards it from your computer. It's not like deleting a file and sending it to the trash can where you can recycle the file if you change your mind. This is a permanent move.

Therefore, you must use this command with caution. You do not want to accidentally erase a file from your computer that you may need in the future. This shows the fact that there is a positive and negative side to this command. However, there is one advice that I will give you: use rm-i. This command will require confirmation from you before performing any action. This can actually save you from permanently deleting any essential files. Aside from that warning, now let's look at the syntax and applied example:

• rm filename
• rm my.txt