Cheatsheet & Examples: cat
cat command is used to read, concatenate, and display the content of files in the terminal. It can also be used to create, view, or merge files.
Display file contents
Example Usage:
cat filename
What it does: Prints the content of the specified file to the terminal.
Command-line Arguments Explained:
- filename: The path to the file being read and displayed.
Concatenate multiple files
Example Usage:
cat file1 file2 > combined
What it does:
Combines the contents of file1 and file2 into a new file called combined.
Command-line Arguments Explained:
- file1, file2: The files to be concatenated.
>: Shell redirection operator, not acatargument, used to direct output to a file.
Create or overwrite a file
Example Usage:
cat > newfile
What it does:
Creates a new file named newfile or overwrites an existing one, allowing input to be entered and saved.
Command-line Arguments Explained:
>: Shell redirection operator, not acatargument, used to redirect input to a file.
Display file with line numbers
Example Usage:
cat -n filename
What it does:
Displays the content of filename with line numbers added to each line.
Command-line Arguments Explained:
-n: Enables line numbering for the output.
Append to a file
Example Usage:
cat >> existingfile
What it does:
Adds input from standard input to the end of existingfile without overwriting it.
Command-line Arguments Explained:
>>: Shell redirection operator, not acatargument, used to append output to a file.
Display non-printing characters
Example Usage:
cat -v filename
What it does:
Displays non-printing characters in filename as visible symbols (e.g., tabs as ^I, newlines as $.).
Command-line Arguments Explained:
-v: Enables visualization of non-printing characters.
Show help information
Example Usage:
cat --help
What it does:
Displays a summary of cat command options and usage.
Command-line Arguments Explained:
--help: Shows the help message for thecatcommand.
Pipe file content to another command
Example Usage:
cat file | grep "pattern"
What it does:
Passes the content of file to the grep command for filtering.
Command-line Arguments Explained:
|: Shell pipe operator, not acatargument, used to connect commands.
Squeeze multiple blank lines
Example Usage:
cat -s file1 file2
What it does: Removes extra blank lines between files when outputting their content.
Command-line Arguments Explained:
-s: Squeezes multiple consecutive blank lines into one.
Number non-empty lines
Example Usage:
cat -b filename
What it does:
Displays the content of filename with line numbers, excluding blank lines.
Command-line Arguments Explained:
-b: Enables line numbering, skipping blank lines.
