How to perform a for loop on each character in a string in Bash?

Question

I have a variable like this:

words="这是一条狗。"

I want to make a for loop on each of the characters, one at a time, e.g. first character="这", then character="是", character="一", etc.

The only way I know is to output each character to separate line in a file, then use while read line, but this seems very inefficient.

• How can I process each character in a string through a for loop?

Answer 1

You can use a C-style for loop:

foo=string
for (( i=0; i<${#foo}; i++ )); do
  echo "${foo:$i:1}"
done

${#foo} expands to the length of foo. ${foo:$i:1} expands to the substring starting at position $i of length 1.