How do I split a string on a delimiter in Bash?

To split a string on a delimiter in Bash, you can use several methods depending on your needs. Here are the most common approaches:

1. Split into an Array with read and IFS

Set the Internal Field Separator (IFS) to your delimiter and use read -ra to split the string into an array.

Example: Split on commas (,):

string="apple,banana,cherry"
IFS=',' read -ra arr <<< "$string"

# Access elements
echo "${arr[0]}"   # Output: apple
echo "${arr[1]}"   # Output: banana
echo "${#arr[@]}"  # Output: 3 (number of elements)

2. Split with Parameter Expansion

Replace the delimiter with a space and convert the string into an array:

string="one:two:three"
delimiter=":"
arr=(${string//$delimiter/ })  # Replace delimiter with spaces

echo "${arr[2]}"  # Output: three

Note: This works only if the string does not contain spaces.

3. Use awk for Advanced Splitting

For multi-character delimiters or field extraction:

string="name|age|city"
echo "$string" | awk -F'|' '{print $2}'  # Output: age

4. Split with tr and Process Line-by-Line

Convert the delimiter to newlines and iterate:

string="dog;cat;bird"
echo "$string" | tr ';' '\n' | while read -r item; do
  echo "Item: $item"
done

Output:

Item: dog
Item: cat
Item: bird

5. Extract Specific Fields with cut

Get the nth field (e.g., 2nd field):

string="red,green,blue"
echo "$string" | cut -d',' -f2  # Output: green

Key Notes

• Delimiters with Special Characters: Escape them (e.g., IFS=$'\t' for tabs).
• Empty Elements: Leading/trailing delimiters create empty array elements (e.g., ",a,b," splits into "", "a", "b", "").
• Multi-Character Delimiters: Use awk or sed (e.g., awk -F'::' '{...}').

Full Example: Split and Iterate

# Split a CSV string into an array
csv="item1,item2,item3"
IFS=',' read -ra items <<< "$csv"

for item in "${items[@]}"; do
  echo "Processing: $item"
done

Output:

Processing: item1
Processing: item2
Processing: item3

Edge Cases

• Handle Empty Strings:

  string=",,apple,,"
  IFS=',' read -ra arr <<< "$string"
  echo "${#arr[@]}"  # Output: 5 (includes empty elements)

• Trim Whitespace (if needed):

  string="  apple ,  banana  "
  IFS=',' read -ra arr <<< "$string"
  # Trim spaces for each element
  arr=("${arr[@]// /}")  # Remove all spaces

Use these methods to split strings for parsing CSV, paths (e.g., $PATH), or configuration data!