Day 3: Working with Text Editors and Files

Objectives

• Learn to use basic text editors: nano and gedit.
• Understand file manipulation commands: viewing, searching, and editing text files.
• Get familiar with text processing tools like cat, grep, and awk.

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1. Using Text Editors

nano Text Editor

nano is a simple and user-friendly command-line text editor.

1. Opening a File with nano

   • To create or open a file:

     $ nano filename

2. Basic nano Commands

   • Save Changes: Press Ctrl + O, then press Enter.
   • Exit nano: Press Ctrl + X.
   • Cut Text: Press Ctrl + K.
   • Paste Text: Press Ctrl + U.
   • Search Text: Press Ctrl + W.

gedit Text Editor

gedit is a graphical text editor for the GNOME desktop environment.

1. Opening a File with gedit

   • To create or open a file:

     $ gedit filename &

   • The & symbol runs gedit in the background, allowing the terminal to be used for other commands.

2. Basic gedit Features

   • Save Changes: Click Save in the menu or press Ctrl + S.
   • Exit gedit: Click Close in the menu or press Ctrl + Q.
   • Find and Replace: Click Search in the menu, then Find... or Replace....

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2. File Manipulation Commands

Viewing Text Files

1. cat Command

   • Concatenate and display file content:

     $ cat filename

   • Display multiple files:

     $ cat file1 file2

2. more Command

   • View file content one screen at a time:

     $ more filename

   • Navigate through the file using Space for the next page, b for the previous page, and q to quit.

3. less Command

   • Similar to more but with more navigation options:

     $ less filename

   • Navigate using arrow keys, Space for the next page, b for the previous page, and q to quit.

Searching Text Files

1. grep Command
   • Search for specific text in a file:

     $ grep "search_term" filename

   • Search recursively in all files in a directory:

     $ grep -r "search_term" directory

   • Common options:
     • -i: Ignore case.
     • -n: Show line numbers.
     • -v: Invert match, showing lines that do not match the search term.

Editing Text Files

1. sed Command

   • Stream editor for filtering and transforming text.
   • Replace text in a file:

     $ sed 's/old_text/new_text/' filename

   • Replace text globally in the file:

     $ sed 's/old_text/new_text/g' filename

   • Save changes to the same file:

     $ sed -i 's/old_text/new_text/g' filename

2. awk Command

   • Pattern scanning and processing language.
   • Print specific columns from a file:

     $ awk '{print $1, $3}' filename

   • Print lines matching a pattern:

     $ awk '/pattern/ {print}' filename

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Practical Exercises

Exercise 1: Using nano

1. Open a new file with nano:

   $ nano myfile.txt

2. Write the following text:

   Hello, World!
   This is a sample file.

3. Save the file and exit nano.

Exercise 2: Using gedit

1. Open a new file with gedit:

   $ gedit myfile2.txt &

2. Write the following text:

   Welcome to gedit.
   Enjoy editing text files!

3. Save the file and close gedit.

Exercise 3: Viewing Files with cat, more, and less

1. Create a sample text file with multiple lines using nano or gedit.
2. Display the content using cat:

   $ cat myfile.txt

3. View the content one page at a time using more:

   $ more myfile.txt

4. Navigate through the file using less:

   $ less myfile.txt

Exercise 4: Searching Files with grep

1. Search for the word "sample" in myfile.txt:

   $ grep "sample" myfile.txt

2. Search for the word "sample" ignoring case:

   $ grep -i "sample" myfile.txt

3. Display line numbers while searching:

   $ grep -n "sample" myfile.txt

Exercise 5: Editing Files with sed and awk

1. Replace the word "Hello" with "Hi" in myfile.txt using sed:

   $ sed 's/Hello/Hi/' myfile.txt

2. Print the first and second columns of myfile.txt using awk:

   $ awk '{print $1, $2}' myfile.txt