判断

判断目录是否存在

if [ -d "$dir" ]; then
  echo "$dir exists"
else
  echo "$dir does not exist"
fi

判断命令是否存在

if ! command -v jq &>/dev/null; then
  echo "jq not installed"
  exit 1
fi

判断命令是否执行成功

if mount bpffs /sys/fs/bpf -t bpf 2>/dev/null; then
  echo "mount bpffs success"
fi