Swapping or switching 2 lines using sed


 
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# 1  
Old 10-14-2008
Power Swapping or switching 2 lines using sed

I made a script that can swap info on two lines using a combination of awk and sed, but was hoping to consolidate the script to make it run faster. If found this script, but can't seem to get it to work in a bash shell. I keep getting the error "Too many {'s". Any help here would be appreciated:

Swapping two lines with sed
Assume, in the following file I want to swap the third with the fifth line:
Code:
one
two
five
four
three
six
seven

Then this could be done with the following sed script:

Code:
sed -ne '
 3!{p;d;}
 h;n;:1
 4!{N;b1}
 G;h;n;p;g;p' numbers

Note, it's a 4, not a 5 in the sed script!

Last edited by Neo; 12-21-2013 at 01:31 PM.. Reason: code taggies
# 2  
Old 10-15-2008
hi

I think below perl script can help you a little.

Code:
$file=shift;
$l1=shift;
$l2=shift;
open FH,"<$file";
while(<FH>){
	$arr[$.]=$_;
}
close FH;
for($i=1;$i<=$#arr;$i++){
	if($i==$l1){
		print $arr[$l2];
	}
	else{
		if ($i==$l2){
			print $arr[$l1];
		}
		else{
			print $arr[$i];
		}
	}
}


Below sed script can not adress your question flexbily, but should throw some light on that.
Code:
1
2
5
4
3
6

Code:
1
2
3
4
5
6

Code:
sed -n '/5/ !{
p
}
/5/ {
h
n
G
x
n
G
p
}'


Last edited by summer_cherry; 10-15-2008 at 04:19 AM..
# 3  
Old 10-16-2008
I'm sorry, but I'm new to unix and am not familiar with perl...in that script, where do i tell the script what file to sort...also, how do i tell it which lines to swap?
# 4  
Old 10-16-2008
With awk:

Code:
awk 'NR==3 {
  s=$0
  getline;s=$0"\n"s
  getline;print;print s
  next
}1' file

Regards
# 5  
Old 10-16-2008
Quote:
Originally Posted by Franklin52
With awk:

Code:
awk 'NR==3 {
  s=$0
  getline;s=$0"\n"s
  getline;print;print s
  next
}1' file

Regards
Awesome! is there any way to make this code dynamic? I wanted to put some shell variables in here...For example, If I wanted to start with line $x instead of 3, I would start by replacing NR==3 with NR=="'"$x"'"...where would I input my variable for line 5?

Last edited by LaTortuga; 10-16-2008 at 06:28 PM..
# 6  
Old 10-17-2008
You can use a variable as follow:

Code:
#!/bin/sh

line=3

awk -v var="$line" 'NR==var {
  s=$0
  getline;s=$0"\n"s
  getline;print;print s
  next
}1' file

Regards
# 7  
Old 10-17-2008
Quote:
Originally Posted by Franklin52
You can use a variable as follow:

Code:
#!/bin/sh
 
line=3
 
awk -v var="$line" 'NR==var {
  s=$0
  getline;s=$0"\n"s
  getline;print;print s
  next
}1' file

Regards
Right, so now this code switches line "var" (which for this example is set at 3), with a line two below it...but how do I switch line "var" with say another line defined by another variable, say "var2"?...or would this code not be able to do that?...I know I probably should've asked for this caveat at the outset, my apologies.
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