Process Substitution

This command uses process substitution (<(command)) to pass the output of curl as a file-like input to bash. Let’s break it down:

What’s Happening?

bash <(curl -sL https://raw.githubusercontent.com/v2fly/fhs-install-v2ray/master/install-release.sh)

1. curl -sL <URL>
   • Fetches the script (install-release.sh) from the given URL.
   • -s = Silent mode (no progress/errors shown).
   • -L = Follow redirects (if any).
2. Process Substitution (<(...))
   • <(command) creates a temporary named pipe (FIFO) or /dev/fd file descriptor containing the output of curl.
   • Instead of saving the script to disk, Bash treats the output as a temporary “file” for input.
3. bash <file>
   • The script is executed directly by bash without being saved to disk.

Why Use Process Substitution?

• No Temporary File Needed
  Avoids writing the script to disk (cleaner, no cleanup required).
• Security Consideration
  Prevents tampering (if the script were saved, malware could modify it before execution).
• One-Liner Convenience
  Combines download + execution in a single command.

Alternatives (Without Process Substitution)

# Download to a file, then run (less secure)
curl -sL https://.../install-release.sh -o install.sh
bash install.sh
rm install.sh  # Cleanup

# Pipe directly (no process substitution)
curl -sL https://.../install-release.sh | bash

• Piping (| bash) works but may miss script features (e.g., $0 detection fails).
• Process substitution preserves script behavior as if it were a local file.

Key Takeaway

Process substitution (<()) is used here to treat the downloaded script as a file without saving it, combining safety and convenience. It’s a common pattern for remote script execution.