Mistakenly entered a command in terminal in Greek? Auto switch keyboard

If you often type commands in Greek and English, you might have noticed a common annoyance: typing Greek letters by mistake in the terminal, which results in errors like λσ: command not found.

You can automate language switching in your macOS Terminal using a small Bash function and a utility called macism.

Step 1 — Install macism

macism is a command-line tool that lets you control the current macOS input source.
Install it via Homebrew:

brew tap laishulu/homebrew 
brew install macism

You can test it by listing your available input sources:

macism

Typical output:

com.apple.keylayout.ABC 
com.apple.inputmethod.Greek

Step 2 — Add the Bash Hook

Place this function in your ~/.bashrc or ~/.bash_profile:

preexec() { 
  local cmd="$1" 
  local first_char="${cmd:0:1}" 
  if [[ $first_char =~ [Α-Ωα-ω] ]]; then 
    echo "Greek detected → switching to English" 
    macism "com.apple.keylayout.ABC" 
  fi 
} 
trap 'preexec "$BASH_COMMAND"' DEBUG

How It Works

• trap 'preexec "$BASH_COMMAND"' DEBUG triggers before every command execution.
• The function checks the first character of the command.
• If it matches a Greek letter ([Α-Ωα-ω]), it switches the input method to English (U.S.) using macism.

This ensures that every time you accidentally start typing a Greek command, your keyboard automatically flips back to English.

Optional — Customizing the Language Code

To switch to a different layout, run macism without parameters and note the identifier. Replace "com.apple.keylayout.ABC" with your preferred layout ID.

Example Run

λσ 
Greek detected → switching to English 
bash: λσ: command not found

Afterward, your keyboard switches back to English automatically — so your next command will execute correctly.