Cheat Sheet #day51 - cat

cat Command Cheatsheet

The cat command in Unix/Linux is used to concatenate and display the contents of files. It stands for "concatenate" and is commonly used to read and output file content. Below are the basic and advanced usages of the cat command along with practical examples.

Basic Usage

• Display the contents of a file

    cat filename
  

• Display the contents of multiple files

    cat file1 file2
  

• Concatenate multiple files and redirect the output to a new file

    cat file1 file2 > newfile
  

Common Options

• Number all output lines

    cat -n filename
  

• Show non-printing characters (except for tabs and the end of line)

    cat -v filename
  

• Display line ends with a $ sign

    cat -E filename
  

• Display tabs as ^I

    cat -T filename
  

• Suppress repeated empty output lines

    cat -s filename
  

Examples

• Display a single file

    cat file.txt
  

• Display multiple files

    cat file1.txt file2.txt
  

• Concatenate files and write to a new file

    cat file1.txt file2.txt > newfile.txt
  

• Number all output lines

    cat -n file.txt
  

• Show non-printing characters

    cat -v file.txt
  

• Display line ends

    cat -E file.txt
  

• Display tabs as ^I

    cat -T file.txt
  

• Suppress repeated empty lines

    cat -s file.txt
  

Advanced Usage

• Concatenate files and append to an existing file

    cat file1.txt file2.txt >> existingfile.txt
  

• Create a new file with cat (end input with Ctrl+D)

    cat > newfile.txt
    This is the content of the new file.
  

• Combine cat with other commands using pipes

    cat file.txt | grep "search_term"
  

Practical Tips

• View Large Files: Use cat to quickly view the contents of large files, but consider using less or more for easier navigation.

• Combine Files: Use cat to combine multiple files into a single file.

• Create Files: Use cat to create and quickly input content into new files.

• Use with Caution: Be careful with output redirection (>) to avoid accidentally overwriting important files.

Quick Reference

• Display file contents:

    cat filename
  

• Number all output lines:

    cat -n filename
  

• Show non-printing characters:

    cat -v filename
  

• Display line ends:

    cat -E filename
  

• Display tabs as ^I:

    cat -T filename
  

• Suppress repeated empty lines:

    cat -s filename
  

• Concatenate files:

    cat file1 file2 > newfile
  

• Append to an existing file:

    cat file1 file2 >> existingfile
  

• Create a new file:

    cat > newfile.txt
  

This cheatsheet covers the essential commands and options for using cat effectively, from displaying file contents to concatenating and creating new files. Adjust the commands according to your specific requirements and environment.