Prevent Claude from using bash commands over its built-in tools

.claude_hooks_enforce-builtin-tools.sh

#!/usr/bin/env bash
# ~/.claude/hooks/enforce-builtin-tools.sh
#
# PreToolUse hook: blocks file-inspection shell commands and redirects
# Claude to use the appropriate built-in Claude Code tool instead.
#
# Install:
#   mkdir -p ~/.claude/hooks
#   cp enforce-builtin-tools.sh ~/.claude/hooks/
#   chmod +x ~/.claude/hooks/enforce-builtin-tools.sh
#
# Then add the hook config to ~/.claude/settings.json (see settings.json).

INPUT=$(cat)
COMMAND=$(echo "$INPUT" | jq -r '.tool_input.command // empty')

# Exit early if no command was found in the input
if [[ -z "$COMMAND" ]]; then
  exit 0
fi

# Strip leading whitespace and get the first token (the binary being called)
TRIMMED=$(echo "$COMMAND" | sed 's/^[[:space:]]*//')
BINARY=$(echo "$TRIMMED" | awk '{print $1}')

# Helper: deny with a message sent back to Claude via stderr
deny() {
  echo "$1" >&2
  exit 2
}

case "$BINARY" in

  find)
    deny "Use the Glob tool to find files by pattern (e.g. '**/*.ts'), or the Grep tool to search by content. Do not use the 'find' shell command."
    ;;

  grep|rg|ag|ack)
    deny "Use the Grep tool to search file contents. Do not use '${BINARY}' as a shell command."
    ;;

  ls|dir)
    deny "Use the LS tool to list directory contents. Do not use '${BINARY}' as a shell command."
    ;;

  cat)
    deny "Use the Read tool to read file contents. Do not use 'cat'."
    ;;

  head|tail)
    deny "Use the Read tool to read file contents (it supports line offsets). Do not use '${BINARY}'."
    ;;

  less|more|bat)
    deny "Use the Read tool to read file contents. Do not use '${BINARY}'."
    ;;

  sed)
    # Allow sed when used in a pipeline (likely transforming output, not reading files directly).
    # Block it when it's the first command and appears to be reading a file.
    if echo "$COMMAND" | grep -qE '(^|\|)\s*sed\s.+\s\S+\.[a-zA-Z]+'; then
      deny "Use the Read tool to read file contents, and the Edit or MultiEdit tool to make changes. Do not use 'sed' to read or modify files directly."
    fi
    ;;

  awk)
    # Same heuristic as sed: block when it looks like awk is reading a file directly.
    if echo "$COMMAND" | grep -qE '(^|\|)\s*awk\s.+\s\S+\.[a-zA-Z]+'; then
      deny "Use the Read tool to read file contents. Do not use 'awk' to read files directly."
    fi
    ;;

  wc)
    # wc -l on a file is often used as a substitute for knowing file size before reading.
    # Allow wc in pipelines, block direct file reads.
    if echo "$COMMAND" | grep -qE '^wc\s'; then
      deny "Use the Read tool to inspect file contents. Do not use 'wc' to read files directly."
    fi
    ;;

esac

# All other Bash commands are allowed
exit 0

.claude_settings.json

{
  // other settings
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          {
            "type": "command",
            "command": "~/.claude/hooks/enforce-builtin-tools.sh"
          }
        ]
      }
    ]
  }
}