Linux print line from file

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Sunday, 12 April 2015

Sed Command in Linux — Print Lines in a File

This is the first article of the «Super sed ‘ Series», in which we will learn how to print lines in a file using line numbers and regular expressions.

Before we directly jump to the main content, every learner should know what sed is. Here is the brief introduction of the Super sed :

• sed stand for Stream EDitor and it being based on the ed editor, it borrows most of the commands from the ed . It was developed by Lee E. McMahon of Bell Labs.
• sed offers large range of text transformations that include printing lines, deleting lines, editing line in-place, search and replace, appending and inserting lines, etc.
• sed is useful whenever you need to perform common editing operations on multiple lines without using ‘vi’ editor.
• Whenever sed is executed on an input file or on the contents from stdin, sed reads the file line-by-line and after removing the trailing newline, places it in the «Pattern space», where the commands are executed on them after conditions (as in case of regex matching) are verified, and then printed on the stdout.

Printing Lines from a File using sed

Before we start, just remember two points:

1. sed «p» command lets us print specific lines based on the line number or regex provided.
2. sed with option -n will suppress automatic printing of pattern buffer/space. So, we would want to use this option. (Explained in later section)

For our better understanding, let us have a file sedtest.txt with contents as follows:

A. sed — Print Lines with Line Number

1. Print ‘N’th line

This will print ‘N’th line in the FILE.txt .

Example:
To print 1st line,

While, to print last line,

Let us see, what if we had not used option -n , what would have been the result.

You can easily see that 5th line is printed twice, one from pattern buffer/space and other is the result of sed ‘5p’ .

2. Print all Lines starting from ‘M’th up to ‘N’th

This will print the block of lines starting at line number M and ending at line number N .

Example:
To print 3rd line to 8th line.

Similarly, in order to print lines starting from 5th up to last line, you would run-

3. Print Every ‘N’th Line Starting from ‘M’th Line

This will print Mth line and every Nth line coming after that.

Example:
To print every alternate line staring from 2nd one.

B. sed — Print Lines with Regular Expression/Pattern

1. Print lines containing a Pattern

This will print the line that contains the pattern provided.

2. Print lines excluding a Pattern

This will print all those lines which do not contain the pattern provided.

3. Print Block of lines starting from pattern matching line

This will start printing the lines from the one where pattern matches, till ‘N’th line.

Of course, in order to print all the lines starting from pattern matching line till the end, you would use ‘/PATTERN/,$p’ as follows —

4. Print Block of lines ending at pattern matching line

This will start printing the lines starting from the ‘N’th line, till the one where pattern matches.

So, here, if you wish to start from first line and end at a line matching a pattern, you would use —

5. Print Block of lines between two Pattern matches

This will start printing lines from 1st pattern match till 2nd pattern match.

That was all about the first article on sed command. More articles on sed are coming soon. So, stay tuned. Of course, do not forget to share your feedback in the comment section below.

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How to Display Specific Lines of a File in Linux Command Line

How do I find the nth line in a file in Linux command line? How do I display line number x to line number y?

In Linux, there are several ways to achieve the same result. Printing specific lines from a file is no exception.

To display 13th line, you can use a combination of head and tail:

Or, you can use sed command:

To display line numbers from 20 to 25, you can combine head and tail commands like this:

Or, you can use the sed command like this:

Detailed explanation of each command follows next. I’ll also show the use of awk command for this purpose.

Display specific lines using head and tail commands

This is my favorite way of displaying lines of choice. I find it easier to remember and use.

Print a single specific line

Use a combination of head and tail command in the following function the line number x:

You can replace x with the line number you want to display. So, let’s say you want to display the 13th line of the file.

Explanation: You probably already know that the head command gets the lines of a file from the start while the tail command gets the lines from the end.

The “head -x” part of the command will get the first x lines of the files. It will then redirect this output to the tail command. The tail command will display all the lines starting from line number x.

Quite obviously, if you take 13 lines from the top, the lines starting from number 13 to the end will be the 13th line. That’s the logic behind this command.

Print specific range of lines

Now let’s take our combination of head and tail commands to display more than one line.

Say you want to display all the lines from x to y. This includes the xth and yth lines also:

Let’s take a practical example. Suppose you want to print all the the lines from line number 20 to 25:

Use SED to display specific lines

The powerful sed command provides several ways of printing specific lines.

For example, to display the 10th line, you can use sed in the following manner:

The -n suppresses the output while the p command prints specific lines. Read this detailed SED guide to learn and understand it in detail.

To display all the lines from line number x to line number y, use this:

Use AWK to print specific lines from a file

The awk command could seem complicated and there is surely a learning curve involved. But like sed, awk is also quite powerful when it comes to editing and manipulating file contents.

NR denotes the ‘current record number’. Please read our detailed AWK command guide for more information.

To display all the lines from x to y, you can use awk command in the following manner:

It follows a syntax that is similar to most programming language.

I hope this quick article helped you in displaying specific lines of a file in Linux command line. If you know some other trick for this purpose, do share it with the rest of us in the comment section.

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Write a bash script to print a particular line from a file

Given a file, name file.txt, out task is to write a bash script which print particular line from a file.

Content of file.txt:

Syntax in Bash Script

1. awk :
2. sed :
3. head :

Examples:

Print a line from single file

To print 4th line from the file then we will run following commands. The output of following lines will be “articles”.

1. awk :
2. sed :
3. head :

Print a line from multiple files

Suppose we have two files, file1.txt and file2.txt, We can use the above commands and print particular line from multiple files by ‘&’.

1. awk:
2. sed:
3. head:

This article is contributed by Sahil Rajput. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

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Unix Sed Tutorial: Printing File Lines using Address and Patterns

Let us review how to print file lines using address and patterns in this first part of sed tutorial.

We’ll be posting several awesome sed tutorials with examples in the upcoming weeks.

Unix Sed Introduction

• sed is a “non-interactive” stream-oriented editor. Since its an “non-interactive” it can be used to automate editing if desired.
• The name sed is an abbreviation for stream editor, and the utility derives many of its commands from the ed line-editor (ed was the first UNIX text editor).
• This allows you to edit multiple files, or to perform common editing operations without ever having to open vi or emacs.
• sed reads from a file or from its standard input, and outputs to its standard output.
• sed has two buffers which are called pattern buffer and hold buffer. Both are initially empty.

Unix Sed Working methodology

This is called as one execution cycle. Cycle continues till end of file/input is reached.

1. Read a entire line from stdin/file.
2. Removes any trailing newline.
3. Places the line, in its pattern buffer.
4. Modify the pattern buffer according to the supplied commands.
5. Print the pattern buffer to stdout.

Printing Operation in Sed

Linux Sed command allows you to print only specific lines based on the line number or pattern matches. “p” is a command for printing the data from the pattern buffer.

To suppress automatic printing of pattern space use -n command with sed. sed -n option will not print anything, unless an explicit request to print is found.

Let us first create thegeekstuff.txt file that will be used in all the examples mentioned below.

5 Sed ADDRESS Format Examples

Sed Address Format 1: NUMBER

This will match only Nth line in the input.

# sed -n ‘N’p filename

For example, 3p prints third line of input file thegeekstuff.txt as shown below.

Sed Address Format 2: NUMBER1

N with “p” command prints every Nth line starting from line M.

# sed -n ‘M

2p prints every 2nd line starting from 3rd line as shown below.

Sed Address Format 3: START,END

M,N with “p” command prints Mth line to Nth line.

# sed -n ‘M,N’p filename

For example, 4,8p prints from 4th line to 8th line from input file thegeekstuff.txt

Sed Address Format 4: ‘$’ Last Line

$ with “p” command matches only the last line from the input.

# sed -n ‘$’p filename

For example, $p prints only the last line as shown below.

Sed Address Format 5: NUMBER,$

N,$ with “p” command prints from Nth line to end of file.

# sed -n ‘N,$p’ filename

For example 4,$p prints from 4th line to end of file.

6 Sed PATTERN Format Examples

Sed Pattern Format 1: PATTERN

PATTERN could be unix regular expression. The below command prints only the line which matches the given pattern.

# sed -n /PATTERN/p filename

For example, following prints the line only which matches the pattern “Sysadmin”.

Sed Pattern Format 2: /PATTERN/,ADDRESS

# sed -n ‘/PATTERN/,Np’ filename

For example, following prints lines which matches the pattern to Nth line, from input. 3rd line matches the pattern “Hardware”, so it prints from 3rd line to 6th line.

Sed Pattern Format 3: ADDRESS,/PATTERN/

It prints from the Nth line of the input, to the line which matches the pattern. If the pattern doesnt match, it prints upto end of the input.

# sed -n ‘N,/PATTERN/p’ filename

For example, 4th line matches the pattern “Security”, so it prints from 3rd line to 4th line.

Sed Pattern Format 4: /PATTERN/,$

It prints from the line matches the given pattern to end of file.

# sed -n ‘/PATTERN/,$p’ filename

Sed Pattern Format 5: /PATTERN/,+N

It prints the lines which matches the pattern and next N lines following the matched line.

# sed -n ‘/PATTERN/,+Np’ filename

For example, following prints the 5th line which matches the pattern /Storage/ and next two lines following /Storage/.

Sed Pattern Format 6: /PATTERN/,/PATTERN/

Prints the section of file between two regular expression (including the matched line ).

# sed -n ‘/P1/,/P2/p’ filename

For example, 5th line matches “Storage” and 8th line matches “Design”, so it prints 5th to 8th.

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This is a great addition to my bag of tricks. I knew about grep to find patterns, but sed looks like a good way to fix things in multiple files. Thanks!

format #2
invalid command code

# sed -n ‘4,’p file
sed: 1: “4,p”: expected context address

oh, sorry, my mistake =)
# sed -n ‘4,$’p file

2’p thegeekstuff.txt
sed: invalid command code

2’p thegeekstuff.txt
works fine. (gsed = GNU sed)

# — variant for UNIX (non GNU) sed:

> sed -n ‘3,$’ thegeekstuff.txt
prints every 2nd line starting from 3rd

> sed -n ‘3,$’ thegeekstuff.txt
prints every 3rd line starting from 3rd

Useful link:
http://sed.sourceforge.net/sed1line.txt
awesome tricks with 1-line scripts for sed
(http://ant0.ru/sed1line.html – russian version of sed1line document)

However, in the very last example, the match is on ‘Design’, not on ‘Website’.

Usefull Article, thanks Ramesh…

Hi,
Very good tutorial. Really it helped me a lot. Thank u sooooooo much.

Very good tutorial for sed. Thank you very much.

For the below command the output is not being limited to N’th (6th) line.

$sed -n ‘/Sysadmin/,6p’ thegeekstuff.txt

1. Linux – Sysadmin, Scripting etc.
2. Databases – Oracle, mySQL etc.
3. Hardware
4. Security (Firewall, Network, Online Security etc)
5. Storage
6. Cool gadgets and websites
10.Windows- Sysadmin, reboot etc.
================================

Please let me know where i am doing wrong.

The given command will print the lines which matches for the word ‘Sysadmin’ to 6th line in a file (if available) . Since first line matches for the word ‘Sysadmin’ it prints the first line to 6th line. And 10th line (last) line also matches to the given word, so it prints.

These examples are very useful.
I wonder how to apply “sed” to print the following format.
input data output data
a1 b1 a1 b1 a3 b3 a5 b5 a1 b1 b3 b5
a2 b2 —-> a2 b2 a4 b4 a6 b6 —-> a2 b2 b4 b6
a3 b3
a4 b4
a5 b5
a6 b6

Thank you in advance 🙂

In an organisation one wants to know how many programmers are there. The employee data is stored in a file called ‘personnel’ with one record per employee. Every record has field for designation. How can sed be used to print only the records of all employees who are programmers ?

How to find last 10 lines if I don’t know size of file?

It’s helping a lot ……thank uuuuuuuuuuuuuu

Hi ramesh
whats wrong with this code?

=========
I want to use sed for printing a file line by line

sorry for foolish question
the answer is :

for ((i=1;i> newfile
done

for ((i=1;i doomhammer65ir November 27, 2011, 3:27 pm

Hi,
There are some problems I am facing with linux right now.
This is what I am doing to generate a cryptographic signature fron bash script….

step1. I encrypt a text : encrypt(bhavyakailkhurabhavyakailkhura) and get a encrypted string sdfghjklsdfghjklzxcvbnmghjkdfghjkzxcvbnmzxc
step2. I copy that string manually from mouse no commands used and append it with a file..

$ cat textfile.txt…
user=bhavya
signature=

step3. Using “sed” on text file I send text between “<” and “>” to another file bhavya.txt
step4. now when I try to decrypt bhavya.txt it say error in reading file. I checked the text is same as encrypted. When I copy original encrypted text in step 1 and decrypt It works.

I think the problem is sed command changes spacing between text its not same as copying using mouse. Do you have any idea how we can solve this problem?

Sorry for clumsy and lengthy explanation.

I would like to subsitute the comma in the amount enclosed in double quote only and leave all the comma as it. How can I do it?R,112074121151,45891,SMITH,JOHN ,HELLEN,”$1,078.67″,1118.69
Thank you.
Hedy

It’s very helpful to understand what sed is!.

i want to print the last 5 lines of a file using sed command.

hi., i want to know the syntax for printing multiple different lines using sed.
like sed -n ‘2,4’p,’6,8’p thegeekstuff.txt..
want to print lines 2 to 4 and 6 to 8., how to do it.

Rahul Prasad,
Try this command for emulating tail -5.
sed -e :a -e ‘$q;N;6,$D;ba’ thegeekstuff.txt

Shiva,
You can try this command.
sed -n ‘2,4 p; 6,8 p’ thegeekstuff.txt
or
sed -n -e ‘2,4 p’ -e ‘6,8 p’ thegeekstuff.txt

I just started learning sed and I am glad I found this article. You made it very illustrative with all the examples. Thank you

Hi All,
How to print 3th line first and 2nd line next??
3. Hardware
2. Databases – Oracle, mySQL etc.

Hi., i want to change the extension of my all files which are in current dir. via using sed command………….. , i m trying this code in a shell script
#!/bin/bash
for file in *
do
NEW=”echo $file|sed -f ‘s/.txt.new/.txt/g’”
mv $file $NEW
done

when i m running this shell script, o/p is :-
mv: target `\’s/txt.new/txt/g\” is not a directory

Plz fix it……………. thanx in advance………

has anyone got issues with

Sed Pattern Format 6: /PATTERN/,/PATTERN/
Prints the section of file between two regular expression (including the matched line ).

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