Add words to a text file using a single terminal command (no editors)

I'm new to Linux. I need to edit a .conf file from the open terminal only and not using any text editors. That is, can I add words and sentences to a config file from an open terminal?

Example: command /home/.../file.conf -add 'abcd' to the 23rd line and so on. And finally, save it.

Is it possible to search a specific word in that config file and add new text to the next line of that config file using only the command?

I usually do this way when I am programming my script to do same what you are asking but programmatically.

echo "Hello you!" >> myfile.txt
echo "this is 2nd line text" >> file.txt
echo "last line!" >> file.txt

Voila! You got it. Important to note >> means adding new line to existing file meanwhile > just simply overwrite everything.

Adding words and sentences to a config file from open terminal can be easily achieved with sed.

sed -i '23iabcd' file.conf

inserts at line 23 the text abcd into file file.conf

-i does the modification directly to file file.conf.

If you want to use awk then:

awk -v n=23 -v s="abcd" 'NR == n {print s} {print}' file > file.conf

The following adds one line after SearchPattern.

sed -i '/SearchPattern/aNew Text' SomeFile.txt

It inserts New Text one line below each line that contains SearchPattern.

To add two lines, you can use a \ and enter a newline while typing New Text.

 sed -i '/pattern/a \
line1 \
line2' inputfile

You can also use the printf command.

To add lines to your file

$ printf "\nThis is a new line to your document" >> file.txt

To overwrite the file

$ printf "This overwrites your file" > file.txt