5_cat_echo.md

echo command

It prints the strings that are passed as arguments to the standard output.

echo is usually used in shell scripts to display a message or output the results of other commands.

1. Display a line of text on standard output.

   echo Hello, World!

2. Display a line of text containing a double quote.

   $ echo 'Hello "Linux"'

   $ echo "Hello "Linux""

3. Display a message containing special characters.

   Use the -e option to enable the interpretation of the escape characters.

   $ echo -e "You know nothing, Jamal.\n\t- Linux"

4. echo can be used with redirect operator to output to a file and not standard output.

   $ echo "Test Page" > testpage

5. To append to a file

   $ echo "Test Page" >> testpage

cat command

cat stands for concatenate

1. Display the contents of the file

   $ cat /etc/passwd

2. View contents of multiple files

   $ cat file1.txt file2.txt

3. Create a file with cat command

   cat > file.txt

   Will create a file 'file.txt' and allows user to type the content on the console, until user press CTRL-D to exit

4. Display Line numbers in file

   cat -n file.txt

5. Redirect output of a file to a new file

   cat file1.txt > file2.txt

   Careful, existing contents of file2.txt will be overwritten by contents of file1.txt file.

6. Appending to an existing file

   cat file1.txt >> file2.txt

   Contents of file1.txt will be appended to file2.txt