Cheatsheet & Examples: head
The head command displays the beginning of a file, typically the first 10 lines by default. It is useful for quickly previewing files without opening them entirely.
Display the first 10 lines of a file
Example Usage:head filename.txt
What it does:
Prints the first 10 lines of the specified file.
Command-line Arguments Explained:
filename.txt: The file whose content is to be displayed.
Display a specified number of lines
Example Usage:head -n 5 filename.txt
What it does:
Prints the first 5 lines of the file.
Command-line Arguments Explained:
-n 5: Specifies the number of lines to display (in this case, 5).filename.txt: The file to be read.
Display a specified number of bytes
Example Usage:head -c 100 filename.txt
What it does:
Prints the first 100 bytes of the file.
Command-line Arguments Explained:
-c 100: Specifies the number of bytes to display (in this case, 100).filename.txt: The file to be read.
Suppress headers when viewing multiple files
Example Usage:head -q -n 3 file1.txt file2.txt
What it does:
Displays the first 3 lines of each file without printing filenames as headers.
Command-line Arguments Explained:
-q: Suppresses the display of filenames for multiple files.-n 3: Specifies the number of lines to display (3 in this case).
Display the first 10 lines of standard input
Example Usage:head
What it does:
Reads and displays the first 10 lines of input from the standard input stream (e.g., user input or piped data).
Command-line Arguments Explained:
- No arguments: Uses default behavior (first 10 lines).
Display the first 10 lines of multiple files
Example Usage:head file1.txt file2.txt
What it does:
Prints the first 10 lines of each specified file, including their filenames as headers.
Command-line Arguments Explained:
file1.txt: The first file to be read.file2.txt: The second file to be read.
Display the first 5 lines of a file and write to another file
Example Usage:head -n 5 filename.txt > output.txt
What it does:
Extracts the first 5 lines of filename.txt and saves them to output.txt.
Command-line Arguments Explained:
-n 5: Specifies the number of lines to display (5 in this case).filename.txt: The source file.> output.txt: Redirects the output to a new file.
Follow a file's content in real time
Example Usage:head -f log.txt
What it does:
Continuously displays new lines added to log.txt as they are written, useful for monitoring logs.
Command-line Arguments Explained:
-f: Enables "follow" mode, keeping the command running to show updates.log.txt: The file to monitor for new content.
Display the first 10 lines of a file with verbose output
Example Usage:head -v filename.txt
What it does:
Prints the first 10 lines of the file, along with the filename as a header (even for a single file).
Command-line Arguments Explained:
-v: Enables verbose mode, showing filenames for individual files.filename.txt: The file to be read.
