Bash script: test command -o option

Question

I have a piece of code like this:

count=0
until [ -f $filename -o $count -ge 60 ]
do
  count=$((count+1))
  sleep 1
done

I know [ -f $filename -o $count -ge 60 ] is a test command, "-f $filename" tests if the file exists or not, "$count -ge 60" tests if count is greater than or equal to 60, what does "-o" mean?

I googled, can't find the answer, anyone can help?

Answer 1

It's logical OR operator.

From bash documentation:

expr1 -o expr2
    True if either expr1 or expr2 is true.

Answer 2

It is a logical or operation. The code checks if $filename exists once/second for 60 seconds.