UNIX for Dummies Questions & Answers

Hi all! I think someone might be able to solve my problem pretty easily.

I am trying to run a bash loop with 3 variables. I know how to do:

Code:

for var1 in `cat list1`; do for var2 in `cat list2`; do for var3 in `cat list3`; command var1 var2 > var3; done; done; done

However, this will run all permutations between the three variables.
So if I have three files defining var1, var2 and var3, I only want the first line from each file to run in loop1, then the second line of each file to run for loop2, etc....

So if each file as 10 variables, the loop will run 10 times:
first iteration:

Code:

command var1a var1b > var1c

second iteration and so forth...

Code:

command var2a var2b > var2c

Is this easy to do??
Thanks in advance!!

Something like this might work for you, this is assuming each file(list1, list2, list3) has the same number of lines:

Code:

ln_cnt=`stat -c %s list1`      # count of lines
for i in 1..${ln_cnt}
do
  var1=`sed -n "${i}p" list1`  # Load line from first file
  var2=`sed -n "${i}p" list2`  # Load same line# from 2nd file
  var3=`sed -n "${i}p" list3`  # Load same line# from 3rd file
  command $var1 $var2 $var3;   # Run command
done

paste will put all 3 files into a single stream. by default the separator is a tab.

Code:

paste file1 file2 file3 |
while IFS=$'\t' read -r var1 var2 var3; do
    echo command "$var1" "$var2" '>' "$var3"
done

replace echo if look good.

Please post what Operating System and version you are using.

Code:

uname -a # Blotting anything confidential with X characters

There is some variation in the paste command - including whether it will accept more than two input filenames.

aside @spacebar: stat -c "%s" will give you the byte count of the file, not the line count. I don't know of any format char to output the line count.