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cat Linux Command
cat command is used to create, read & concatenate files in Linux/ Unix machines
2019-08-21
2022-10-05

cat command is used to create, read & concatenate files in Linux/ Unix machines.

1. Creating a file with content

Lets create a file with name file1.txt and put following three lines of content into it.

First you need to run the following command to create a file

cat >file1.txt

When you press enter after the above command, it waits for the file content input. You can give multi line input and once you are done you need to press CTRL + D to save and exit.

2. Displaying file contents

Following command shows the content of given file

cat file1.txt

3. Display content from multiple files

Following command shows content from file1.txt followed by content from file2.txt

cat file1.txt file2.txt

4. Copy the contents of one file to another file

Following command copies content from file1.txt to file2.txt

cat file1.txt > file2.txt

5. Append the contents of one file to the end of another file

Following command appends content of file1.txt to the end of file2.txt

cat file1.txt >> file2.txt

6. Display content in reverse order

Following command displays content of file1.txt in reverse order

tac file1.txt

7. Open dashed files

Following command displays content of -dashfile

cat -- "-dashfile"

8. If the file has a lot of content and can’t fit in the terminal

cat "filename" | more

9. Merge the contents of multiple files

cat "filename1" "filename2" "filename3" > "merged_filename"

10. Display Line Numbers before every line

Following command prefixes line numbers before each line from content

cat -n file1.txt

Following is an example for that

$ cat -n file1.txt
     1	line-1
     2	line-2
     3	line-3
     4	line-4

11. Display content with More & Less Options

If a file having a large number of content that won’t fit in the output terminal and the screen scrolls up very fast, we can use parameters more and less with the cat command as shown below.

cat song.txt | more
cat song.txt | less

More Options

Option Description
-e Shows $ at the end of the content
-t To see tabs in file, this shows tabs with ^I
-s Removes repeated empty lines in content
-E Highlights the end of line