How to copy the first few lines of a giant file, and add a line of text at the end of it using some Linux commands?

Question

How do I copy the first few lines of a giant file and add a line of text at the end of it, using some Linux commands?

Answer 1

I am assuming what you are trying to achieve is to insert a line after the first few lines of of a textfile.

head -n10 file.txt >> newfile.txt echo "your line >> newfile.txt tail -n +10 file.txt >> newfile.txt 

If you don't want to rest of the lines from the file, just skip the tail part.

Answer 2

The head command can get the first n lines. Variations are:

head -7 file head -n 7 file head -7l file 

which will get the first 7 lines of the file called "file". The command to use depends on your version of head. Linux will work with the first one.

To append lines to the end of the same file, use:

echo 'first line to add' >>file echo 'second line to add' >>file echo 'third line to add' >>file 

or:

echo 'first line to add second line to add third line to add' >>file 

to do it in one hit.

So, tying these two ideas together, if you wanted to get the first 10 lines of the input.txt file to output.txt and append a line with five "=" characters, you could use something like:

( head -10 input.txt ; echo '=====' ) > output.txt 

In this case, we do both operations in a sub-shell so as to consolidate the output streams into one, which is then used to create or overwrite the output file.