What

The filter mode (-e/--show-matches) outputs matched values. This adds a flag to output their original 0-based indexes instead.

Why

When using fzy in scripts (specifically in filter mode, -e), it is often far more robust to receive the index of the selected item rather than its string value.

This becomes critical when the input list is pre-formatted with rich content. Consider a script that displays a list of git branches, formatting each line with:

• The branch name
• The commit hash in yellow
• The commit message in grey with emojis
• ANSI control characters to apply the colors

If fzy returns the full selected string, the calling script must parse this complex line, full of control characters and extra data, just to figure out which original item was selected. This process is brittle and error-prone.

The -I flag provides a much cleaner solution. The script receives a simple integer (the index), which it can directly use to reference its original, unformatted data array. This makes index-based selection patterns simple and reliable.

Changes

Core implementation:

• Added index field to scored_result struct to preserve original positions during search
• Implemented choices_getindex() with bounds checking
• Modified filter output in fzy.c to emit indexes when flag is set

CLI interface:

• Added -I/--show-indexes flag to options parsing
• Updated help text and man page

Testing:

• Added test_choices_get_index() to verify index tracking through search and sort

Usage

Without the flag, fzy outputs the matched values, sorted by relevance:

$ echo -e "apple\nbanana\napricot\navocado" | fzy -e "a"
apple
apricot
avocado
banana

With the -I flag, fzy outputs the 0-based indexes of those same matches:

$ echo -e "apple\nbanana\napricot\navocado" | fzy -e "a" -I
0
2
3
1

This enables robust index-based selection patterns in scripts:

# Create an array of files
FILES=($(find -type f))

# Let the user select a file using fzy and get its index
# Then, use the index to retrieve the original, clean filename from the array
SELECTED_INDEX=$(printf '%s\n' "${FILES[@]}" | fzy -e "query" -I)

# Open the selected file
vi "${FILES[$SELECTED_INDEX]}"