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cat – Concatenates Multiple Files and Prints to Standard Output

The cat command is a Linux command that concatenates multiple files and prints them to standard output. It is a simple and useful command that allows users to view the contents of multiple files without having to open each file individually.

Overview

The basic syntax for the cat command is:

cat [OPTION]... [FILE]...

The cat command can take one or more file names as arguments. When multiple file names are provided, cat will concatenate the contents of each file and display them on the screen.

For example, to concatenate the contents of two files named file1.txt and file2.txt, you would use the following command:

cat file1.txt file2.txt

This would display the contents of file1.txt followed by the contents of file2.txt.

You can also use wildcards to concatenate multiple files at once. For example, to concatenate all .txt files in the current directory, you would use the following command:

cat *.txt

This would display the contents of all .txt files in the current directory.

The cat command can also be used to create new files or append to existing files. To create a new file, you can use the following command:

cat > newfile.txt

This will create a new file named newfile.txt and allow you to type in the contents of the file. To save the file, press Ctrl + D.

To append to an existing file, you can use the following command:

cat >> existingfile.txt

This will append the contents of standard input to the end of the file named existingfile.txt.

Options

The cat command has several options that can be used to modify its behavior. The following table lists the available options:

Option Description
-A Equivalent to -vET. Displays non-printing characters and appends $ to end of each line.
-b Number non-blank output lines.
-e Equivalent to -vE. Displays non-printing characters and appends $ to end of each line.
-E Displays $ at the end of each line.
-n Number all output lines.
-s Squeezes multiple blank lines into a single blank line.
-t Equivalent to -vT. Displays non-printing characters and appends ^I to tabs.
-T Displays ^I at tabs.
-u Disables output buffering.

Troubleshooting Tips

  • If you receive an error message that says “No such file or directory”, make sure that the file name is spelled correctly and that the file exists in the specified location.
  • If you are using wildcards to concatenate multiple files, make sure that the wildcard pattern matches the files you want to concatenate.
  • If you are creating a new file with cat, make sure that you press Ctrl + D to save the file when you are done typing the contents.

Notes

  • The cat command can be used with pipes (|) to send the output of one command as input to another command.
  • The cat command is often used in shell scripts to concatenate files or to display the contents of a file on the screen.

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