composer/composer · critical · RuntimeException

Failed to execute {command} {errorOutput}

Error message

Failed to execute {command}

{errorOutput}

What it means

Thrown by GzipDownloader::extract() on non-Windows when the shell command `gzip -cd` fails AND the PHP zlib extension is not loaded. On non-Windows Composer first tries the system gzip binary; only if that fails does it fall back to ext-zlib. With neither available, extraction is impossible.

Source

Thrown at src/Composer/Downloader/GzipDownloader.php:47

        $targetFilepath = $path . DIRECTORY_SEPARATOR . $filename;

        // Try to use gunzip on *nix
        if (!Platform::isWindows()) {
            $command = ['sh', '-c', 'gzip -cd -- "$0" > "$1"', $file, $targetFilepath];

            if (0 === $this->process->execute($command, $ignoredOutput)) {
                return \React\Promise\resolve(null);
            }

            if (extension_loaded('zlib')) {
                // Fallback to using the PHP extension.
                $this->extractUsingExt($file, $targetFilepath);

                return \React\Promise\resolve(null);
            }

            $processError = 'Failed to execute ' . implode(' ', $command) . "\n\n" . $this->process->getErrorOutput();
            throw new \RuntimeException($processError);
        }

        // Windows version of PHP has built-in support of gzip functions
        $this->extractUsingExt($file, $targetFilepath);

        return \React\Promise\resolve(null);
    }

    private function extractUsingExt(string $file, string $targetFilepath): void
    {
        $archiveFile = gzopen($file, 'rb');
        $targetFile = fopen($targetFilepath, 'wb');
        while ($string = gzread($archiveFile, 4096)) {
            fwrite($targetFile, $string, Platform::strlen($string));
        }
        gzclose($archiveFile);
        fclose($targetFile);
    }

View on GitHub (pinned to 6ffc117740)

Solutions

1. Install gzip in the environment: apt-get install -y gzip (or apk add gzip on Alpine).
2. Enable/install the PHP zlib extension (ext-zlib) so the PHP fallback works.
3. Use a PHP image that ships ext-zlib (most official images do).
4. Prefer dist formats that use XzDownloader/TarDownloader if the provider offers non-gzip archives.

Example fix

# before: neither gzip nor ext-zlib available
composer install   # GzipDownloader fails

# after: install gzip
apt-get update && apt-get install -y gzip
# or ensure ext-zlib in PHP:
docker-php-ext-install zlib   # rebuild PHP with zlib

// Verify gzip binary or ext-zlib before relying on GzipDownloader
$hasGzip = false === stripos(PHP_OS_FAMILY, 'Windows')
    ? (function_exists('shell_exec') ? (bool) trim((string) shell_exec('command -v gzip')) : false)
    : true; // Windows uses ext-zlib path
$hasZlib = extension_loaded('zlib');
if (!$hasGzip && !$hasZlib) {
    throw new \RuntimeException('No gzip extraction method available: install gzip or enable ext-zlib');
}

When it happens

Trigger: Installing a package whose dist is a .gz single-file archive (not a tar/zip) on a minimal Linux image that lacks the gzip binary and where PHP was compiled without --enable-zlib.

Common situations: Minimal Alpine/Docker images without gzip installed; PHP images built without ext-zlib; stripped-down CI runners.

Related errors

• Could not decompress the archive, enable the PHP rar extensi
• The zip extension and unzip/7z commands are both missing, sk
• Can not compress to %s format
• The Zip Util requires PHP's zip extension
• You must enable the openssl extension to use a secure proxy.

AI-assisted analysis of composer/composer@6ffc117740 (2026-08-07). Data as JSON: /api/errors/65580ef32f89f399. Report an issue: GitHub.