Login or Register to Ask a Question and Join Our Community


Shell Programming and Scripting

deleting lines from file

Login to Discuss or Reply to this Discussion in Our Community

 
Thread Tools Search this Thread
Top Forums Shell Programming and Scripting deleting lines from file
# 1  
Old 03-03-2010
deleting lines from file
We have a server that logs transactions to a file. I want to write a script that will delete the first 50 lines of the file daily without renameing the file or moving the file.
# 2  
Old 03-03-2010
In early sed versions you can run this script

Code:
sed '1,3d'

I don't remember the option that forces to overwrite the file with the modified text, but I think is -i

---------- Post updated at 02:00 PM ---------- Previous update was at 01:59 PM ----------

PS: In my script I delete lines 1 to 3
# 3  
Old 03-03-2010
-i is the option. But that's possible not widely available (certainly on UNIX).

Another option is ed:

Code:
$ cat file1
1
2
3
4
5

$ ed file1 << !
1,3d
w
q
!

$ cat file1
4
5

(and of course perl will do it easily!)
# 4  
Old 03-03-2010
Question Just thinking about awk
Could awk read the file, line-by-line into an array
then starting at element 51 begin writing back out to the same file?
# 5  
Old 03-03-2010
Code:
cat file | awk ' NR > 50 ' > file

Code:
cat file | sed -n "51,$ p" > file

Code:
perl -i -ne ' if($. > 50) { print $_ ; } ' file

# 6  
Old 03-03-2010
Quote:
Originally Posted by joeyg
Could awk read the file, line-by-line into an array
then starting at element 51 begin writing back out to the same file?
Not like this:
Code:
awk  'NR >= START  {X[NR]=$0} END {for( x = START; x<=NR; x++ ) print X[x] }' START=51 file1 > file1

But you might get away with it like this:
Code:
awk  'NR >= START  {X[NR]=$0} END {for( x = START; x<=NR; x++ ) print X[x] > "file1"}' START=51 file1


Quote:
Originally Posted by anbu23
Code:
cat file | awk ' NR > 50 ' > file

Code:
cat file | sed -n "51,$ p" > file

Some UUOC's there!
# 7  
Old 03-03-2010
Code:
printf '1,50d\nwq!\n' | ex -s myFile
{ rm myFile; sed -e '1,50d' > myFile; } < myFile
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Deleting selected lines in a file

Hi Guys , I have two files say a1 and a2 having following contents a1 dag wfd a2 dag wfd chire hcm I want to delete only the lines in a2 which are in a1 and final output of a2 should be a2 chire hcm (6 Replies)
Discussion started by: Pradeep_1990
6 Replies

2. Shell Programming and Scripting

Deleting specific lines in a file

Hello, I have a file filled with dates, such as: 04-08-2011 message 04-08-2011 message 03-08-2011 message 01-08-2011 message 31-07-2011 message 24-07-2011 message 15-07-2011 message 13-12-2008 message 26-11-2007 message And I want to delete those lines whose date is older than 10... (5 Replies)
Discussion started by: asanchez
5 Replies

3. Shell Programming and Scripting

Re: Deleting lines from big file.

Hi, I have a big (2.7 GB) text file. Each lines has '|' saperator to saperate each columns. I want to delete those lines which has text like '|0|0|0|0|0' I tried: sed '/|0|0|0|0|0/d' test.txt Unfortunately, it scans the file but does nothing. file content sample:... (4 Replies)
Discussion started by: dipeshvshah
4 Replies

4. Shell Programming and Scripting

Deleting certain new lines from a file with shell

Good morning!!! Im a newbie with shell programing and i was wondering if there is a way to delete certain new lines from a file, here is an example of my current file: >seq_0 GTGAGATTGCTAATGAGCTGCTTTTAGGGGGCGTGTTGTGCTTGCTTTCC AACTTTTCTAGATTGATTCTACGCTGCCTCCAGCAGCCACCCCTCCCATC... (11 Replies)
Discussion started by: machalita
11 Replies

5. UNIX for Advanced & Expert Users

Deleting lines from a file

How I can delete 100 lines anywhere in a file without opening a file and without renaming the file. (11 Replies)
Discussion started by: Nirgude07
11 Replies

6. Shell Programming and Scripting

Deleting lines ending with . from a file

HI I'm looking to delete lines ending with .tk from below data file --------- abc.tk mgm.tk dtk mgmstk ------ I have written below code ---- sed '/.tk *$/d' dat_file.txt > temp.txt ---- But its deleting all the lines ending with tk. I need to delete only the lines ending .tk my... (5 Replies)
Discussion started by: shekhar_v4
5 Replies

7. UNIX for Dummies Questions & Answers

Deleting whole lines from a file

I have a file with 65 sets of 35 coordinates, and would like to isolate these coordinates so that I can easily copy the coordinates to another file. The problem is, I've got a 9 line header before each set of coordinates (so each set is 44 lines long). There are a zillion threads out there about... (3 Replies)
Discussion started by: red baron
3 Replies

8. Shell Programming and Scripting

Deleting lines in a file

How do I delete all the lines after the line containing text ***DISCLOSURES*** . I want to delete this line too. Thank you (2 Replies)
Discussion started by: reachsamir
2 Replies

9. Shell Programming and Scripting

Deleting last 2 lines from the file.

Hi I have a file & always I need to remove or delete last 2 lines from that file. So in a file if I have 10 lines then it should return me first 8 lines. Can someone help me? (4 Replies)
Discussion started by: videsh77
4 Replies

10. Shell Programming and Scripting

deleting lines in a log file

Is there an easy way to delete the first so many lines in a log file? like I have a log file that has 10000 lines, i want to just get rid of the first 9000. (2 Replies)
Discussion started by: BG_JrAdmin
2 Replies
Login or Register to Ask a Question