How Do I Ignore Blank Lines in Grep?

grep stands for Global Regular Expression Print. It has many functionalities, i.e., searching in a file, searching only names of a file, grep recursively, etc. grep is considered a powerful command in the linux command portfolio when it comes to searching. In many cases, we face situations where we don’t need spaces, or there is a need to remove unwanted gaps in our data. One of the most challenging ways of using grep is to ignore or remove blank lines from the text file. This procedure is accomplished through different examples so please read on below to see how its done.

Syntax

grep [pattern] [filename]

After using grep, there comes a pattern. The pattern implies the way we want to use it in removing extra space in the data. Following the pattern, the filename is described through which the pattern is performed.

Prerequisite

To understand the usefulness of grep easily, we need to have Ubuntu installed on our system. Provide user details by providing username and password to have privileges in accessing the applications of Linux. After logging in, open the application and search for a terminal or apply the shortcut key of ctrl+alt+T.

By Using [: blank:] Keyword

You can create a file either on text editor or with a command line in the terminal. To create a file on the terminal, including the following commands.

$ echo “text to be entered in a file” > filename.txt

There is no need to create a file if it is already present. Just display it using the appended command:

$ cat filename.txt

Suppose we have a file named bfile having a text extension. Text written in these files contains spaces between them, as seen in the figure below.

$ echo "my name is guria.
i am a good student.
i read in class 5.

i have one brother and one sister

my mother is a house wife
i want to go to school
" > bfile.txt

Display the file contents as shown below:

$ cat bfile.txt

These blank lines can be removed using a blank command to ignore empty spaces between the words or strings.

$ egrep '^[[:blank:]]*[^[:blank:]#]' bfile.txt

After applying the query, the blank spaces between the lines will be removed, and the output will no longer contain extra space. The first word is highlighted as spaces between the last word of the line and between the first words of the next line are removed. We can also apply conditions on the same grep command by adding this blank function to remove useless space in the output.

By Using [: space:]

Another example of ignoring space is explained here. First lets create our text file on the terminal:

$ echo "my name is hamna

I am a house wife
I want to learn programing

I have one daughter

" > file20

Without mentioning file extension, we will first display the existing file using the command.

$ cat file20

Let’s look at how extra space is removed using the grep command besides the [: space:] keyword. grep’s –v option will help print lines that lack blank lines and extra spacing that is also included in a paragraph form.

$ grep -v '^[[:space:]]*$' file20

You will see that extra lines are removed and output is in sequenced form line-wise. That’s how grep –v methodology is so helpful in obtaining the required goal.

Let’s do another example with the following data file:

$ echo "grep is a versatile command that help new user.

It is used to search file names with the help of commands.

we can go to mannual by using grep man

" > fileg.txt

Output is as follow:

By applying the command, our output file has been obtained. Here, we can see data without spacing between the lines that are consecutively written.

$ grep -v '^[[:space:]]*$' fileg.txt

Besides long commands, we can also go with the short written commands in Linux and Unix to implement grep supports shorthand characters in it.

$ grep '\s' fileg.txt

We have seen how the output is obtained by applying commands from the input. Here, we will learn how input is maintained back from the output.

$ grep '\S' fileg.txt > tmp.txt && mv tmp.txt fileg.txt

Here we will use a temporary text file with extension of text named as tmp to transfer the filtered content back to the original file.

By Using ^#

Let’s create a new data file in order to test this syntax version:

$ echo "graphic designing is a good platform of designing

and making logos business cards

and posters etc. Photoshop

and illustrator are used for that"> fileb.txt

$ cat fileb.txt

The text file includes 4 lines in it, having space between them. These space lines are easily removed using a particular command.

$ grep -Ev "^#|^$" fileb.txt

Regular extended operations are enabled by –E, which allows all regular expressions, especially pipe. A pipe is used as an optional “or” condition in any pattern.”^#”. This shows the matching of text lines in the file that begins with the sign #. “^$” will match with all free spaces in the text or blank lines.

The output shows the complete removal of extra space between the lines present in the data file. In this example, we have seen that in the command that ”^#” comes first, which means the text is matched first. “^$” comes after | operator, so free space is matched afterward.

By Using ^$

Just like the example mentioned above, we will come with the same results because the command is almost the same. However, the pattern is written oppositely. File22.txt is a file, which we are going to use in removing spaces.

$ echo "technical writing is a good feild of studying

it is an analytical field

we can learn many things in it
business writing is its category of writting

Thanku fot learning"> file22.txt

$ grep –v '^$' file22.txt

The same methodology is applied except the working with priority. According to this command, first, free spaces will be matched, then the text files are matched. The output will provide a sequence of lines by removing extra gaps in them.

Other Simple Commands

grep '^..' file22.txt

grep '.' file22.txt

These both are so simple and helps in removing gaps in text lines.

Conclusion

Removing useless gaps in files with the help of regular expressions is quite an easy approach to achieve a smooth sequence of data and maintain consistency. Examples are explained in a detailed manner to enhance your information regarding the topic.