Why does the loop break unexpectedly?

Question

bash

There is a script:

#!/bin/bash

file="/tmp/test.csv"    # 879314 strok

for ((;;))
do

index=0
while read line; do
        array[$index]="$line"
        index=$(($index+1))
done < $file

for ((a=0; a < ${#array[*]}; a++))
do
echo "${array[$a]}" >> /tmp/test-cycle.csv
done

echo > /tmp/test-cycle.csv
done

The essence of the script is as follows, the /tmp/test.csv file is re-read and added line by line to /tmp/test-cycle.csv, after the entire file has been re-read, it is reset (echo > /tmp/test-cycle.csv) and re-read again and line folding.
So, even if I comment out the line echo > /tmp/test-cycle.csv, my cycle for rereading the file does not complete, if I follow the filling of the /tmp/test-cycle.csv file using the tail command, then it pops up " file is truncated".
Please note that my source file has 879314 lines. If you set on a file, for example, from 10k lines, then everything works like clockwork, and with a large file an unexpected truncation occurs, and each time in a different place (i.e. somewhere approximately in the same, but still different)
Why is this happening? please help me to do it right.

Answer 1

I suspect you're just hitting the memory limit that bash allocates for an array.
For example, for ksh93 it is ~4 MB by default. Offhand what is the limitation in bash and how to look at it I will not say.
But in this script, why would you want to create an array at all? You can immediately output to a file

while read line; do
  echo "$line" >> /tmp/test-cycle.csv
done < $file