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Can sed replace every 2 instances it finds in a file? Pattern.

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Top Forums Shell Programming and Scripting Can sed replace every 2 instances it finds in a file? Pattern.
# 8  
Old 03-06-2010
Sure:
Code:
awk '/PORT/ && gsub("PORT",int(i)){i+=0.5}1' file

# 9  
Old 03-06-2010
Sweet, you sir, are a god...

Can you tell me what does this do?

"int(i)){i+=0.5}1"

What can I change if I want it to do every 3 instances or maybe start like at 4000 for the integer?
# 10  
Old 03-06-2010
I believe you want to replace each pair of mentions of PORT with a unique port number, the following does that:
Test file before running script:
Code:
$ cat port_test
1:PORT
2:PORT
3:PORT
4:PORT
5:PORT
6:PORT
7:PORT
8:PORT
9:PORT
11:PORT
12:PORT
13:PORT
14:PORT
15:PORT
16:PORT
17:PORT
18:PORT
19:PORT
21:PORT
22:PORT
23:PORT
24:PORT
$

Test file after running script:
Code:
$ cat port_test
1:1000
2:1000
3:1001
4:1001
5:1002
6:1002
7:1003
8:1003
9:1004
11:1004
12:1005
13:1005
14:1006
15:1006
16:1007
17:1007
18:1008
19:1008
21:1009
22:1009
23:1010
24:1010
$

Script to do the above:
Code:
$ cat port_test.sh
index=1000
STARTLINE=1
ENDLINE=`expr ${STARTLINE} + 1`
while [ ${index} -lt 1500 ]; do
  sed -e ''${STARTLINE}','${ENDLINE}'{
s/PORT/'${index}'/ 
}' port_test > port_test.$$ && \
  cp port_test.$$ port_test
  index=`expr ${index} + 1`
  STARTLINE=`expr ${STARTLINE} + 2`
  ENDLINE=`expr ${STARTLINE} + 1`
done
rm port_test.$$
$

This should work in Bourne and BASH shells.
Increase the value 1500 to reflect the number of lines to be changed in your file, in my example's case it could have been set to 1011.

HTH.
# 11  
Old 03-06-2010
Quote:
Originally Posted by EXT3FSCK
Sweet, you sir, are a god...

Can you tell me what does this do?

"int(i)){i+=0.5}1"

What can I change if I want it to do every 3 instances or maybe start like at 4000 for the integer?
Explanation:
Code:
gsub("PORT",int(i))

substitute all instance of PORT in the current line with the integer of i
Code:
{i+=0.5}1

increase i with 0.5 and print the line

This approach suites for 2 instances:

Quote:
int(0) gives 0
int(0.5) gives 0
int(1) gives 1
int(1.5) gives 1
etc.
If you don't have to much substitutes, you can try some thing like for 3 instances if you want to start with 4000:

Code:
awk -v i="4000" '/PORT/ && gsub("PORT",int(i)){i+=0.33334}1' file

# 12  
Old 03-06-2010
Nicely done, Franklin52.

I took the liberty of building on your solution and parameterizing it. i=starting port number, n=how many times to reuse a port number:
Code:
awk '/PORT/ && gsub("PORT",i){i+=!(++j%n)}1' i=1 n=2 file

Regards,
Alister
Last edited by alister; 03-06-2010 at 07:44 PM..
# 13  
Old 03-06-2010
Quote:
Originally Posted by alister
Nicely done, Franklin52.

I took the liberty of building on your solution and parameterizing it. i=starting port number, n=how many times to reuse a port number:
Code:
awk '/PORT/ && gsub("PORT",i){i+=!(++j%n)}1' i=1 n=2 file

Regards,
Alister
Thanks Alister, this did the trick perfectly.

Thank you, I can't thank you enough.
# 14  
Old 03-07-2010
Quote:
Originally Posted by alister
Nicely done, Franklin52.

I took the liberty of building on your solution and parameterizing it. i=starting port number, n=how many times to reuse a port number:
Code:
awk '/PORT/ && gsub("PORT",i){i+=!(++j%n)}1' i=1 n=2 file

Regards,
Alister
I had something similar to that in mind with a mod operator but with NR:
Code:
awk '/PORT/ && gsub("PORT",i){i+=!(NR%n)}1' i=4000 n=3 file

Regards
Last edited by Franklin52; 03-07-2010 at 08:39 AM..
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