Login or Register to Ask a Question and Join Our Community


Shell Programming and Scripting

Use sed to print first n lines and last n lines of an output.

Login to Discuss or Reply to this Discussion in Our Community

 
Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Use sed to print first n lines and last n lines of an output.
# 1  
Old 07-30-2013
Use sed to print first n lines and last n lines of an output.
Use sed to print first n lines and last n lines of an output.
For example: n=10
Can it be done?
Thanks.
# 2  
Old 07-30-2013
Check "selective printing of certain lines" section on this page

http://www.catonmat.net/blog/wp-cont...9/sed1line.txt
This User Gave Thanks to rajamadhavan For This Post:
carloszhang
# 3  
Old 07-30-2013
Quote:
Originally Posted by rajamadhavan
Check "selective printing of certain lines" section on this page

http://www.catonmat.net/blog/wp-cont...9/sed1line.txt
Hi rajamadhavan, thanks for the reply.
I had seen the page before posting,
but below did not work. Smilie
Code:
$ cat a.txt
1
2
3
4
5
6
7
$ sed 3q -e :a -e '$q;N;4,$D;ba' a.txt
/tools/oss/packages/x86_64-rhel5/sed/default/bin/sed: can't read 3q: No such file or directory
5
6
7

# 4  
Old 07-31-2013
Is your need to print them at one go using a single sed command ?

Can't you go with something like this ?

Code:
sed '3q' filename &&  sed -e :a -e '$q;N;4,$D;ba' filename

This User Gave Thanks to rajamadhavan For This Post:
carloszhang
# 5  
Old 07-31-2013
I know that you asked for a sed solution, but ed is well suited to something like this and only needs to be invoked once to do it. This was tested using a Korn shell, but will work with any shell that recognizes basic Bourne shell syntax:
Code:
#!/bin/ksh
# Usage: tester file count
ed -s "$1" <<-EOF
        1,$2p
        \$-$2+,\$p
        q
EOF

If you save this in a file named tester, make it executable with:
Code:
chmod +x tester

and run it with:
Code:
./tester a.txt 1

where a.txt contains the text shown in the 3rd message in this thread, the output will be:
Code:
1
7

and the output from the command:
Code:
./tester a.txt 5

will be:
Code:
1
2
3
4
5
3
4
5
6
7

These 2 Users Gave Thanks to Don Cragun For This Post:
carloszhang krishmaths
# 6  
Old 07-31-2013
Quote:
Originally Posted by rajamadhavan
Is your need to print them at one go using a single sed command ?

Can't you go with something like this ?

Code:
sed '3q' filename &&  sed -e :a -e '$q;N;4,$D;ba' filename

Hi rajamadhavan,
Actually it's a command output instead of a file,
so your above code seems not applicable.
Thanks.

---------- Post updated at 02:50 PM ---------- Previous update was at 02:45 PM ----------

I googled and got some alternative solutions.
Code:
(head -3; tail -3) < a.txt

but how to apply it to a command output?
I tried below but failed.
Code:
cat a.txt | (head -3; tail -3)

Thanks.
# 7  
Old 07-31-2013
Just for the fun of it, using awk
Code:
awk '{a[NR]=$0} NR<=n {print} END{for (i=NR-n+1;i<=NR;i++) print a[i]}' n=3 file

This prints the first 3 and last 3 records of file

Or if you like it to the output
cat file | awk '{a[NR]=$0} NR<=n {print} END{for (i=NR-n+1;i<=NR;i++) print a[i]}' n=3
This User Gave Thanks to Jotne For This Post:
carloszhang
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

sed print all lines between second and third identical lines

I am trying to extract a table of data (mysql query output) from a log file. I need to print everything below the header and not past the end of the table. I have spent many hours searching with little progress. I am matching the regexp +-\{99\} with no problem. I just can't figure out how to print... (5 Replies)
Discussion started by: godfreydanials
5 Replies

2. AIX

Print output of grep command in multuple lines

HI All, I am using grep command to serach a pattern in a list of files and storing the output in a variable. Then i am applying some logic on that variable to get the required output. But Thing is that when the pattern is present mutiple times in a file, i am getting the output of grep in a... (3 Replies)
Discussion started by: goutam sahoo
3 Replies

3. Shell Programming and Scripting

sed command : print lines having no # at the begining

I am trying to print those line which has no # in the begining of the line. The sed I used for this purpose as shown below is not giving the required output. echo 'PDE 5600' | sed -n 's/^\!#/&/p' Where lies the problem:confused: (3 Replies)
Discussion started by: hiten.r.chauhan
3 Replies

4. UNIX for Dummies Questions & Answers

sed print certain lines matching variable

I have a very large results file, and a list of filters grep -wf filterlist.txt datafile.txt > outfile.txt The above line works but is very slow and I'm wondering how to make it faster. The items in my filterlist are only relevant to the first column. I don't care if any item in the... (1 Reply)
Discussion started by: sayb
1 Replies

5. Shell Programming and Scripting

Print duplicate only lines as normal output - Awk

input output a1 100 200 XYZ_X a1 98 188 ABC (2 Replies)
Discussion started by: quincyjones
2 Replies

6. Shell Programming and Scripting

print lines AFTER lines cointaining a regexp (or print every first and fourth line)

Hi all, This should be very easy but I can't figure it out... I have a file that looks like this: @SRR057408.1 FW8Y5CK02R652T length=34 AGCAGTGGTATCAACGCAGAGTAAGCAGTGGTAT +SRR057408.1 FW8Y5CK02R652T length=34 FIIHFF6666?=:88@@@BBD:::?@ABBAAA>8 @SRR057408.2 FW8Y5CK02TBMHV length=52... (1 Reply)
Discussion started by: kmkocot
1 Replies

7. Solaris

sed command to print lines after expression

Hi guys. I need a sed command to print like 10 lines after a regular expression is found in the log. Can anyone help me out. Thanks ---------- Post updated at 10:52 AM ---------- Previous update was at 10:34 AM ---------- never mind. I just did the search bewteen two expressions. (1 Reply)
Discussion started by: jamie_collins
1 Replies

8. Shell Programming and Scripting

read file-print lines in sed

Hello! Im trying to read file contents. Then, print out every line that has "/bens/here" in the file that was read. cat /my/file.now | sed '/bens/here/p' I keep getting the error asking if I need to predeclare sed? What does predeclaring sed mean? Thanks! Ben (2 Replies)
Discussion started by: bigben1220
2 Replies

9. Shell Programming and Scripting

sed print all lines after pattern match

HiCan someone show me how to print all lines from a file after a line matching a pattern using sed?Thanks (13 Replies)
Discussion started by: steadyonabix
13 Replies

10. Shell Programming and Scripting

Sed one-liner to print specific lines?

I need to print specific lines from a file, say 2-5, 8, 12-15, 17, 19, 21-27. How do I achieve this? (2 Replies)
Discussion started by: Ilja
2 Replies
Login or Register to Ask a Question