Shell脚本中的循环

Question

i have two sets of data, say a=file1 file2 file3 and b=location1 location2 location3 . Now i need to loop through and copy file1 to location1 , file2 to location2 and file3 to location3 .

If I use for loop, then after the first iteration of the the inner loop, it should go back to the outer loop, take the second value, go to the inner loop and take the second value and so on. Basically, the inner loop should not iterate for every value in the outer loop.

Is there a way to do this?

Thanks in advance. Sudhir

Answer 1

It sounds like you're getting too complicated:

a=(file1 file2 file3)
b=(location1 location2 location3)

for (( idx=0; idx<${#a[@]}; idx++ )); do
    cp -v "${a[idx]}" "${b[idx]}"
done

Answer 2

You can create bash arrays and make it work for you:

declare -a f=( "file1" "file2" "file3" )
declare -a d=( "location1" "location2" "location3" )
c=0
for i in ${f[@]}; do
   echo $i ${d[$c]}
   ((c++))
done

Or without arrays something like this script should also work for you:

ci=0
for i in file1 file2 file3; do 
   ((ci++))
   cj=1
   for j in location1 location2 location3; do
      [[ $ci = $cj ]] && echo $i $j && break
     ((cj++))
   done
done

OUTPUT:

file1 location1
file2 location2
file3 location3

Answer 3

For sure $SHELL is simplest here, although once you start doing arrays with bash that advantage starts to dissipate ;-) So, just for comparison, here is a simple, non-oneliner perl approach:

 #!/usr/bin/env perl
 my @arraya = qw/ file1 file2 file3/ ; 
 my @arrayb = qw/ location1 location2 location3/ ;
 foreach my $i ( 0 .. $#arraya ) {`cp $arraya[$i] $arrayb[$i]` }

@arraya and @arrayb can be constructed programmatically into very large lists with /m// matching and filtering, grep ing, find ing, etc.

cf the perl based rename tool.