Visit Our UNIX and Linux User Community


Read the specified line number from file


 
Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Read the specified line number from file
# 1  
Old 12-18-2009
Read the specified line number from file

Hi Guys,
I am new to unix.
Actually i want help in writing an single command where
i can actually read specific line number in file where the line number will be passed to command as parameter.

ex.
1 a
2 b
3 c
4 d

And to my command i pass as 2.
so i should get output as 2 b

---------- Post updated at 05:28 PM ---------- Previous update was at 05:25 PM ----------

i implemented this by below code
Code:
head -n parameter | tail -n 1

but if file is big this will degrade the performance.

But i need to have this as in single line only.
And if possible without awk.
# 2  
Old 12-18-2009
Code:
sed '2!d' yourfile

Number = your wanted line number.
# 3  
Old 12-18-2009
Hi.

Code:
n=3
$ sed "${n}!d" file
or
$ sed -n "${n}p" file
or
awk -v n=$n 'NR == n' file

# 4  
Old 12-18-2009
Quote:
Originally Posted by zaxxon
Code:
sed '2!d' yourfile

Number = your wanted line number.
Hi zaxxon,

Thanks for reply.
Can you please explain me what this command does.
i tried reading man sed in shell but it didn't help
# 5  
Old 12-18-2009
Code:
$ num=3
$ gawk -v n=$num 'NR==n{print;exit}' file

# 6  
Old 12-18-2009
Tools Here is another approach

num=3
cat -n samplefile.txt | grep " $num" | cut -f2
# 7  
Old 12-18-2009
You might want to check websites for sed tutorials etc. or get a good book about it like sed&awk from O'Reilly.

It means
  • 2 ____ when the address is line 2
  • !d ____ do not delete it - ie. it will be printed

The opposite would have been:
Code:
sed -n '2p' infile

Which have meant to not print out every line but only the address you want to process.

Previous Thread | Next Thread
Test Your Knowledge in Computers #104
Difficulty: Easy
Unix is a family of multitasking, portable, multi-user computer operating systems, which do not have time-sharing capability.
True or False?

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

How to read a file starting at certain line number?

I am new to ksh scripts. I would like to be able to read a file line by line from a certain line number. I have a specific line number saved in a variable, say $lineNumber. How can I start reading the file from the line number saved in $lineNumber? Thanks! (4 Replies)
Discussion started by: dcowboys13
4 Replies

2. Shell Programming and Scripting

How to read file line by line and compare subset of 1st line with 2nd?

Hi all, I have a log file say Test.log that gets updated continuously and it has data in pipe separated format. A sample log file would look like: <date1>|<data1>|<url1>|<result1> <date2>|<data2>|<url2>|<result2> <date3>|<data3>|<url3>|<result3> <date4>|<data4>|<url4>|<result4> What I... (3 Replies)
Discussion started by: pat_pramod
3 Replies

3. Shell Programming and Scripting

Need a program that read a file line by line and prints out lines 1, 2 & 3 after an empty line...

Hello, I need a program that read a file line by line and prints out lines 1, 2 & 3 after an empty line... An example of entries in the file would be: SRVXPAPI001 ERRO JUN24 07:28:34 1775 REASON= 0000, PROCID= #E506 #1065: TPCIPPR, INDEX= 003F ... (8 Replies)
Discussion started by: Ferocci
8 Replies

4. Shell Programming and Scripting

Read line with particular number of lines

Hi all, I have a file sample.txt abc asd adf daf adw add adv wdf I want to control the number of lines to read Like if i give input as ./script_name 2 5 required output asd adf daf (2 Replies)
Discussion started by: krux_rap
2 Replies

5. Shell Programming and Scripting

Write $line number into textfile and read from line number

Hello everyone, I don't really know anything about scripting, but I have to manage to make this script, out of necessity. #!/bin/bash while read -r line; do #I'm reading from a big wordlist instructions using $line done Is there a way to automatically write the $line number the script... (4 Replies)
Discussion started by: bobylapointe
4 Replies

6. Shell Programming and Scripting

How to read from specific line number in shell script?

I have a text file which is having 30000 lines in it. I have to create a xml file for each 10000 lines until all the lines in the text files are written. Also please help how can i get number of lines in the text file in a shell variable? (19 Replies)
Discussion started by: vel4ever
19 Replies

7. UNIX for Dummies Questions & Answers

How to read contents of a file from a given line number upto line number again specified by user

Hello Everyone. I am trying to display contains of a file from a specific line to a specific line(let say, from line number 3 to line number 5). For this I got the shell script as shown below: if ; then if ; then tail +$1 $3 | head -n $2 else ... (5 Replies)
Discussion started by: grc
5 Replies

8. Shell Programming and Scripting

bash: read file line by line (lines have '\0') - not full line has read???

I am using the while-loop to read a file. The file has lines with null-terminated strings (words, actually.) What I have by that reading - just a first word up to '\0'! I need to have whole string up to 'new line' - (LF, 10#10, 16#A) What I am doing wrong? #make file 'grb' with... (6 Replies)
Discussion started by: alex_5161
6 Replies

9. Shell Programming and Scripting

how to get the data from line number 1 to line number 100 of a file

Hi Everybody, I am trying to write a script that will get some perticuler data from a file and redirect to a file. My Question is, I have a Very huge file,In that file I have my required data is started from 25th line and it will ends in 100th line. I know the line numbers, I need to get all... (9 Replies)
Discussion started by: Anji
9 Replies

10. Shell Programming and Scripting

How to get the line number from while read

I have a file TXTPROCESS.TXT.20071129 in which line 1 contains the file name and rest of the records are data. The file data looks like this: TXTPROCESS.TXT.20071129 DIVD20071129 INTR20071129 BALN20071129 From line 2 onwards the first 4 characters defines individual process. What I... (2 Replies)
Discussion started by: skymirror
2 Replies

Featured Tech Videos