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Suppose you have a file, a large file, and you want to display its contents. How would you do it?

You obviously don't want to print out the entire contents of the file, as that's not very practical. You might want to print some selective lines; perhaps you'd use a regular expression to parse the file and print only the matches.

This article will explain several methods.

Skipping lines using head and tail commands

The following example uses five of the most commonly used Bash commands to do this:

tail fileName.txt
head fileName.txt
tail -n fileName.txt # here n is an integer
head -n fileName.txt # here n is an integer
tail +n fileName.txt # prints all lines starting from
# the nth file

tailThe command prints the last ten lines of a file, while the head command prints the first ten lines of a file.

When you use the command with –n option tail, it prints the last n lines. Conversely, when you use the command with –n option head, it prints the first n lines.

It is important to note that n here is an integer, so when you execute the command, you must replace n with an integer.

The fifth method is a bit tricky. It ignores the first (n – 1) rows and prints all the rows after that.

Skip the first n lines using vim

You can also skip first n lines using Vim editor. Vim is a console-based text editor that allows you to create and change any text document efficiently.

To use Vim for the first time, you must install it. Do this with the following command:

$ sudo apt install vim

Now that Vim is installed, we get into the business part of our goal, which is to skip the first n lines using Vim.

We will do this by using an intermediate file. We will first copy the contents of the old file into the new file; then, we will delete the first n lines of the new file.

We will use input and output redirection to copy the contents of one file to another file. If you have taken an operating system course, you should have heard of the ppfdt table (process file descriptor table).

By default, the first descriptor points to stdin (or the keyboard), the second to stdout (or the monitor), and the third to stderror.

Consider the following script for further understanding.

cat 0<old_file.txt 1>new_file.txt # copies old file’s contents to new file

The above command reads the contents of the old file and copies it to the new file. Notice how we use descriptor 0 to read and descriptor 1 to write.

If you find this descriptor confusing, we have something different for you. The following command will also work:

cat <old_file.txt >new_file.txt # copies old file’s contents to new file
cp <old_file.txt >new_file.txt # copies old file’s contents to new file

请注意In the second method above, we used the copy command (i.e., cp). It has two parameters: the path of the source file and the path of the destination file.

Now that we have copied the file, open the new file in Vim and use the following command:

vim new_file.txt

Now use Shift+Esc and type the following command in Vim:

:1,nd # here n is an integer number e.g., 2

The above command deletes the first n lines from new_file.txt. Here, d stands for delete.

Using sed to skip first n lines

Creating a new file and then deleting its contents can be cumbersome. Also, if the old file is large, it can consume a lot of extra memory as well.

So, let's look at a simpler way to achieve the same thing:

sed 1,nd old_file.txt # here n is an integer

It is important to note that sedthe command does not modify the old file. Instead, it simply displays the contents of the old file after deleting the first n lines.