Editing Content of file
sed is a powerful command-line tool in Unix/Linux that allows you to perform basic text transformations on an input stream (a file or input from a pipeline). It’s commonly used for:
Searching: Finding lines that match a pattern.
Editing: Modifying text by substituting, inserting, deleting, or appending text.
Displaying: Printing specific lines based on patterns.
The head command in Unix/Linux is used to display the beginning of a file or the first few lines of its content.
Case 1: To collect data from a file that contains continuous lines of text.
# Example:
# Suppose we have data like this
──(kali㉿kali)-[/tmp/temp_workspace]
└─$ cat note.txt
Dave's password list:
Window
rickc137
dave
superdave
megadave
umbrella
Note to myself:
New password policy starting in January 2022. Passwords need 3 numbers, a capital letter and a special character
We want to fetch the data from note.txt. We want all the value from Window to umbrella .
The command sed 's/\bbuf\b/shell/g' replaces every whole word buf with shell in the input text, ensuring it doesn't affect words like buffer.
Case 2: If we want to delete last few lines from file.
Suppose we want to delete last four lines from /etc/john/john.conf file. So, We can use head command with -n and -4 (It is minues 4).
Case 3: Deleting particular line number and displaying its content.
We will use sed command for this.
1d: Tellssedto delete the first line.-i: Edits the file in place.
This deletes the last line from Hosts the file. Run Multiple times to delete multiple last lines.
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