I have two arrays that I want to loop in. I construct those properly and before going into for loop, I do echo them to be sure everything is ok with arrays. But when I run the script, it outputs an error:
l<=: syntax error: operand expected (error token is "<="
I consulted the mighty Google and I understood it suffers from the lack of the second variable, but I mentioned earlier I do echo the values and everything seems to be OK. Here is the snippet..
#!/bin/bash k=0 #this loop is just for being sure array is loaded while [[ $k -le ${#hitEnd[@]} ]] do echo "hitEnd is: ${hitEnd[k]} and hitStart is: ${hitStart[k]}" # here outputs the values correct k=$((k+1)) done k=0 for ((l=${hitStart[k]};l<=${hitEnd[k]};l++)) ; do //this is error line.. let array[l]++ k=$((k+1)) done
The variables in the for loop are echoed correctly but for loop won't work.. where am I wrong?
#
as gniourf_gniourf answered:
"... At some point, k will reach the value ${#hitEnd[@]}, and this is exactly when hitEnd[k] is not defined and expands to an empty string! Bang!"
meaning error output is displayed not at the beginning of the loop, but when k has a greater value than array's indices, pointing an index that array does not include...
That's because at some point ${hitEnd[k]} expands to nothing (it is undefined). I get the same error with ((l<=)). You should write your for loop as:
k=0 for ((l=${hitStart[0]};k<${#hitEnd[@]} && l<=${hitEnd[k]};l++)); do
so as to always have an index k that corresponds to a defined field in the array ${hitEnd[@]}.
Also, instead of
k=$((k+1))
you can just write
((++k))
Done!
Your script revised using better modern bash practice:
#!/bin/bash k=0 #this loop is just for being sure array is loaded while ((k<=${#hitEnd[@]})); do echo "hitEnd is: ${hitEnd[k]} and hitStart is: ${hitStart[k]}" # here outputs the values correct ((++k)) done k=0 for ((l=hitStart[0];k<${#hitEnd[@]} && l<=hitEnd[k];++l)); do ((++array[l])) ((++k)) done
Now, I'm not too sure the for loop does exactly what you want it to... Don't you mean this instead?
#!/bin/bash # define arrays hitStart[@] and hitEnd[@]... # define array array[@] #this loop is just for being sure array is loaded for ((k=0;k<${#hitEnd[@]};++k)); do echo "hitEnd is: ${hitEnd[k]} and hitStart is: ${hitStart[k]}" # here outputs the values correct ((++k)) done for ((k=0;k<${#hitEnd[@]};++k)); do for ((l=hitStart[k];l<=hitEnd[k];++l)); do ((++array[l])) done done
A bit bandaid-y, but you rewrite your for-loop into a while loop:
l="${hitStart[k]}" while [[ "$l" -le "${hitEnd[k]}" ]]; do let array[l]++ k=$((k+1)) l=$((l+1)) done
