bash - do a "while" instead of "for" on an array

grishaoks · 12-12-2008, 08:23 AM

Hello,

I know that if I have an array and I want to go over all the elements in the array I can do something like this:

Code:

ELEMENTS=${#ARRAY[@]}

for (( i=0;i<$ELEMENTS;i++)); do
   echo ${ARRAY[${i}]}
done

Now I have 3 arrays:

Code:

ELEMENTS1=${#arr1[@]}
ELEMENTS2=${#arr2[@]}
ELEMENTS3=${#arr3[@]}

but instead of a "for" loop, I want to use "While". I am trying to do something like this:

Code:

i=0
k=0
j=0
while [ i<$ELEMENTS1 && j<$ELEMENTS2 && k<$ELEMENTS3 ]; do

But it gives me error in the While line that there is no such file or directory. What am I doing wrong?

Thanks in advance,

Greg

The full code is below:

Code:

let tmp=1
ELEMENTS1=${#arr1[@]}
ELEMENTS2=${#arr2[@]}
ELEMENTS3=${#arr3[@]}
i=0
k=0
j=0
while [ i<$ELEMENTS1 && j<$ELEMENTS2 && k<$ELEMENTS3 ]; do
  echo -n $tmp")"
  if [[ ${arr1[${i}]} != NULL ]];
  then
    echo -n ${arr1[${i}]}
    let i++
  fi
  if [[ ${arr2[${j}]} != NULL ]];
  then
    echo -n ${arr2[${j}]}
    let j++
  fi  
  if [[ ${arr3[${k}]} != NULL ]];
  then
    echo ${arr3[${k}]}
    let k++
  fi
  let tmp++
done

Unmindfulawe · 12-12-2008, 12:52 PM

Whenever you use the < operator you must enclose it within [[ ]] otherwise it thinks it is the command in linux to input to a specific file. Whenever you are increasing using ++ it must be enclosed in (( )).
otherwise you will receive a command not found error. I am very new to scripting myself and have found this link to be very helpful.

http://tldp.org/LDP/abs/html/

I modified your code for testing purposes. But I hope this helps.

Code:

let tmp=1
arr1=(1 2 3 4 5 6)
arr2=(A B C D E F G H I)
arr3=(L I N U X S C R I P T )

 ELEMENTS1=(1 2 3 4 5 6)
 ELEMENTS2=(1 2 3 4 5 6 7 8 9)
 ELEMENTS3=(1 2 3 4 5 6 7 8 9 10 11 12)
 i=0
 j=0
 k=0

while [[ $i < ${ELEMENTS1[${i}]} && $j < ${ELEMENTS2[${j}]} && $k < ${ELEMENTS3[${k}]} ]]; do
  echo -n $tmp")"
  if [[ ${arr1[${i}]} != NULL ]];
  	then
		echo -n ${arr1[${i}]};
		((i++))
  fi

  if [[ ${arr2[${j}]} != NULL ]];
	then
		echo -n ${arr2[${j}]}
		((j++))

  fi
	
  if [[ ${arr3[${k}]} != NULL ]];
  	then
   		echo ${arr3[${k}]}
		((k++))
  fi
((tmp++))
done

grishaoks · 12-13-2008, 05:29 AM

Does the code you modified work? Because it doesnt print anything on the screen so I dont think it enters the "While" loop even once...

Unmindfulawe · 12-14-2008, 12:52 AM

Well, when I run the script in the console this is the result of it.

1)1AL
2)2BI
3)3CN
4)4DU
5)5EX
6)6FS

So, the while loop lasts 6 times as $ELEMENTS1 has 6 numbers to iterate.