linux cat command – concatenate files and print on the standard output.
It can also display multiple files concatenated together, and using the shell, its standard output can be redirected from the screen to the file.
syntax
cat [OPTION]... [FILE]...
options
- -A, –show-all
equivalent to -vET - -b, –number-nonblank
number nonempty output lines, overrides -n - -e
equivalent to -vE - -E, –show-ends
display $ at end of each line - -n, –number
number all output lines - -s, –squeeze-blank
suppress repeated empty output lines - -t
equivalent to -vT - -T, –show-tabs
display TAB characters as ^I - -v, –show-nonprinting
use ^ and M- notation, except for LFD and TAB - –help
display this help and exit - –version
output version information and exit
examples
Copy standard input to standard output.
➜ ~ cat
Add the line number of the file(including the blank line) to another file
➜ ~ cat -n examples.txt > test.txt
![](https://www.linuxcommands.site/wp-content/uploads/2019/11/image-132-1024x626.png)
Add the line number of the file (excluding the blank line) and enter it into another file.
➜ ~ cat -b examples.txt > test.txt
Append file content to another file content
➜ ~ cat examples.txt >> test.txt
> :overwrite write
>> :append write
Empty file contents
In Linux, the null
device is basically utilized for discarding of unwanted output streams of a process, or else as a suitable empty file for input streams. This is normally done by redirection mechanism.
And the /dev/null
device file is therefore a special file that writes-off (removes) any input sent to it or its output is same as that of an empty file.
➜ ~ cat /dev/null > test.txt
In server operation, we usually use this method to clear the log file. Of course. You can also use the echo command to achieve the same purpose. ➜ ~ echo "" > test.txt OR ➜ ~ echo > test.txt
Combine multiple file contents into one file
➜ ~ cat examples.txt examples-1.txt > test.txt
To view multiple files
➜ ~ cat examples.txt examples-1.txt