How to set default all product in magento

Open the file  app/code/core/Mage/Page/Block/Html/Pager.php
in an editor and find the following lines:

public function getLimit()
    {
        if ($this->_limit !== null) {
            return $this->_limit;
        }
        $limits = $this->getAvailableLimit();
        if ($limit = $this->getRequest()->getParam($this->getLimitVarName())) {
            if (isset($limits[$limit])) {
                return $limit;
            }
        }
        $limits = array_keys($limits);
 
Replace these lines with this:

public function getLimit()

    {
        //always show all
        return 'all';
        $limits = $this->getAvailableLimit();
        if ($limit = $this->getRequest()->getParam($this->getLimitVarName())) {
            if (isset($limits[$limit])) {
                return $limit;
            }
        }
        $limits = array_keys($limits);
        return $limits[0];
    }

Open the file app\code\core\Mage\Catalog\Block\Product\List/Toolbar.php in an editor and find the following lines:

 public function getAvailableLimit()
    {
        $currentMode = $this->getCurrentMode();
        if (in_array($currentMode, array('list', 'grid'))) {
            return $this->_getAvailableLimit($currentMode);
        } else {
            return $this->_defaultAvailableLimit;
        }
    }
 
Replace these lines with this:
 
 public function getAvailableLimit()

    {
        if ($this->getCurrentMode() == 'list') {
            return array( 'all'=>__('All'),5=>5,10=>10,15=>15,20=>20,25=>25);
        }
        elseif ($this->getCurrentMode() == 'grid') {
            return array( 'all'=>__('All'),9=>9,15=>15,30=>30,);
        }
        return parent::getAvailableLimit();
    }