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# Linux cat Command [ Linux Command Manual](#) The `cat` (short for **concatenate**) command is used to concatenate files and print their content to the standard output device. Its primary purpose is to view and combine files. ### Permissions All users ### Syntax cat **Parameter Description:** * `-n`: Display line numbers. A line number is added before each line of output. * `-b`: Display line numbers, but only for non-empty lines. * `-s`: Squeeze consecutive empty lines into a single empty line. * `-E`: Display a `$` symbol at the end of each line. * `-T`: Display Tab characters as `^I`. * `-v`: Display some non-printing characters. **Usage Instructions:** * Display file content: `cat filename` will output the contents of the specified file to the terminal. * Concatenate files: `cat file1 file2 > combined_file` can concatenate the contents of file1 and file2, and output the result to combined_file. * Create a file: You can use the `cat` command to create a file, for example `cat > filename`, then you can input text and press `Ctrl+D` to save and exit. * Display file in terminal: You can combine `cat` with a pipe (`|`) to display the output of another command, for example `ls -l | cat` will print the output of `ls -l` to the terminal via `cat`. ### Examples **View file content:** Display the contents of the file `filename`. cat filename **Create a file:** Redirect standard input to the file `filename`, overwriting its contents. cat > filename **Append content to a file:** Append standard input to the end of the file `filename`. cat >> filename **Concatenate files:** Merge the contents of file1 and file2 into file3. cat file1 file2 > file3 **Display content of multiple files:** Display the contents of file1 and file2 simultaneously. cat file1 file2 **Use a pipe:** Use the output of the `cat` command as input to another command. cat filename | command **View the last few lines of a file:** Display the last 10 lines of the file `filename`. cat filename | tail -n 10 **Use the -n option to display line numbers:** Display the contents of the file `filename`, with a line number before each line. cat -n filename Use the -b option to display line numbers only for non-empty lines: cat -b filename **Use the -s option to squeeze empty lines:** Display the contents of the file `filename`, squeezing consecutive empty lines. cat -s filename **Use the -t option to display tabs:** Display the contents of the file `filename`, representing tabs with ^I. cat -t filename **Use the -e option to display line endings:** Display the contents of the file `filename`, representing line endings with $. cat -e filename Add line numbers to the content of textfile1 and input it into textfile2: cat -n textfile1 > textfile2 Add line numbers (excluding blank lines) to the content of textfile1 and textfile2, then append the content to textfile3: cat -b textfile1 textfile2 >> textfile3 Clear the content of the file /etc/test.txt: cat /dev/null > /etc/test.txt `cat` can also be used to create disk images. For example, to create a floppy disk image, insert the floppy disk and enter: cat /dev/fd0 > OUTFILE Conversely, if you want to write an image file to a floppy disk, enter: cat IMG_FILE > /dev/fd0 **Note**: * 1. OUTFILE refers to the output image file name. * 2. IMG_FILE refers to the image file. * 3. When writing back from an image file to a device, the device capacity must match. * 4. It is commonly used to create boot disks. [ Linux Command Manual](#)