Shell: how to use 2 variables with for condition

Question

I need to use 2 variables with for condition. For example,

cat days
01072017
02072017
03072017

cat hours
00:00
01:00
02:00
03:00

my shell script sample

 for i in `cat days` & j in `cat hours`
    do
    cat file | grep $i $j >data-$i-$j
    done

I want an output of 3 days * 4hours = 12 files redirected with corresponding data-day-hour

Solution 1

You need to use a nested for loop

   for i in `cat days` 
      do 
        for j in `cat hours`
        do
        cat file | grep  "$i $j"  >data-${i}-${j}
      done
    done

Solution 2

The standard solution for such problem is to make two loops:

for i in $(<days); do
     for j in $(<hours); do
           grep "$i $j" file > data-"$i-$j"
     done
done

Notice that I changed backticks to $() for command substitution, eliminated dead cats, and added double quotes.

Solution 3

You can use this one-liner command to run multiloop , for example you have to restart service on different hosts with different service parameters "i" is for host id and "j " is for service name parameter

for i in 1 2 3 4;do  ssh host$i 'for j in A B C D; do sudo systemctl restart service_$j; done'; done

Note: you must change the "i" and "j" values to your requirements

Comments

[Jeff Schaller]

If I'm reading your comment correctly you want nested loops, not a lock-step single loop through both files ?