Better way to write this script

faizlo · 01-07-2009, 07:23 PM

Hi All,

I have written the following script. I have just repeated some commands, and I am sure there is a more better way to do it. I hope I one of gurus here will help me make it in a better shape. Here is the script:

Code:

#! /bin/sh

sed -i -e "s/test2.xxx/test3.xxx/" -e "s/output2/output3/" makeFV.C
root -l .x makeFV.C

sed -i -e "s/test3.xxx/test4.xxx/" -e "s/output3/output4/" makeFV.C
root -l .x makeFV.C

sed -i -e "s/test4.xxx/test5.xxx/" -e "s/output4/output5/" makeFV.C
root -l .x makeFV.C

sed -i -e "s/test5.xxx/test6.xxx/" -e "s/output5/output6/" makeFV.C
root -l .x makeFV.C

sed -i -e "s/test6.xxx/test7.xxx/" -e "s/output6/output7/" makeFV.C
root -l .x makeFV.C

sed -i -e "s/test7.xxx/test8.xxx/" -e "s/output7/output8/" makeFV.C
root -l .x makeFV.C

sed -i -e "s/test8.xxx/test9.xxx/" -e "s/output8/output9/" makeFV.C
root -l .x makeFV.C

Thanks in advance,

faizlo

colucix · 01-07-2009, 07:51 PM

What about using a for loop over the sequence of numbers between 2 and 8 and use the arithmetic operator to retrieve the numbers between 3 and 9?

faizlo · 01-07-2009, 08:01 PM

Hi,
Thanks for the reply,

I got the first part of your answer (the use of a for loop), yet it is the second part that causes me the headache!
Also, I am not that good at programming

faizlo

faizlo · 01-07-2009, 09:13 PM

This is my first try:

Code:

#! /bin/sh

   for i in `seq 2 1 9`

     sed -i -e "s/test${i}/test${i+1}/" -e "s/output${i}/output${i+1}"
     root -l .x makeFV.C
done

echo "All is done well"

It did not work

I am using sed as you may have noticed, does this need special commands?

faizlo

David the H. · 01-07-2009, 09:47 PM

"${i+1}" is not a mathematical operator. In this construct the + doesn't add anything, it specifies an alternate value in case the variable is null. See parameter substitution at the Advanced Bash Scripting Guide for more details. What you probably want is something like "test$(($i+1))". See arithmetic expansion for that.

Also, it's generally recommended that you use the $() form these days instead of backticks for command substitution. "for i in $(seq 2 1 9)". But actually in this case, seq probably isn't even needed. The for loop will automatically step through each number in the list anyway. "for i in 2 1 9"

faizlo · 01-07-2009, 09:53 PM

Thank you for the response, I will see what I can do about it.

It seems I need to read the abs guide, and I think I should

faizlo

colucix · 01-08-2009, 02:25 AM

Quote:

Originally Posted by faizlo

It seems I need to read the abs guide, and I think I should

This is the correct answer!

Your question about shell programming is very basic, so I tried to encourage to look at the documentation. Anyway, in addition to what already explained by David the H, in bash you can use the extended brace expansion (available since bash version 3) to get a sequence of numbers. Then use the double parentheses construct to do calculations.

An example script to achieve what you're trying to do is

Code:

#!/bin/bash
for i in {2..8}
do
  sed -i -e "s/test$i.xxx/test$((i + 1)).xxx/" -e "s/output$i/output$((i + 1))/" makeFV.C
  root -l .x makeFV.C
done

Hope you will deepen into this. Cheers!