04. Viewing and creating small files cat

Let's look at the cat command (short for concatenation), which is used for manipulating text files.

There are a number of things cat can do including:

  1. Display a (small) text file.
  2. Creating a new text file.
  3. Concatente text files.
  4. Append to a text file.

1) Displaying text files

To display the contents of a file, simply place a filename or the path to a file as an argument.

$ cat fileName
file contents will output here.

2) Creating a text file

cat is also used to create a text file. The following command will allow you to type directly into the terminal to the helloWorld.txt file.

$ cat > helloWorld.txt
type in text here.

To quit, press ctrl+d.

3) Concatenating text files

To place two or more text files together, simply use the following command:

$ cat file1.txt file2.txt > newFile.txt

4) Appending text to a file

To append instead of overwriting, use >>. Appending will simply add to the end of a file instead of starting a new one.

$ cat >> helloWorld.txt
# now type some text here and it will get appended to existing text.

Again, press ctrl+d to when done.


The cat command has a few options which you may find useful.

-E or --show-ends
A $ is shown at each end of line.
-n or --number
Adds line numbers to the beginning of every line.
-s or --squeeze-blank
Compresses groups of blank lines down to a single blank line.
-T or --show-tabs
Shows tab characters at ^I.

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