Find location of a removable SD card

Is there a universal way to find the location of an external SD card?

Please, do not be confused with External Storage.

Environment.getExternalStorageState() returns the path to the internal SD mount point, such as /mnt/sdcard. But the question is about the external SD. How do I get a path like /mnt/sdcard/external_sd (it may differ from device to device)?

I guess I will end with filtering of the output of the mount command by filesystem name. But I'm not sure this way is robust enough.

> Environment.getExternalStorageState() returns path to internal SD mount point like "/mnt/sdcard"

No, Environment.getExternalStorageDirectory() refers to whatever the device manufacturer considered to be "external storage". On some devices, this is removable media, like an SD card. On some devices, this is a portion of on-device flash. Here, "external storage" means "the stuff accessible via USB Mass Storage mode when mounted on a host machine", at least for Android 1.x and 2.x.

> But the question is about external SD. How to get a path like "/mnt/sdcard/external_sd" (it may differ from device to device)?

Android has no concept of "external SD", aside from external storage, as described above.

If a device manufacturer has elected to have external storage be on-board flash and also has an SD card, you will need to contact that manufacturer to determine whether or not you can use the SD card (not guaranteed) and what the rules are for using it, such as what path to use for it.

---

UPDATE

Two recent things of note:

First, on Android 4.4+, you do not have write access to removable media (e.g., "external SD"), except for any locations on that media that might be returned by getExternalFilesDirs() and getExternalCacheDirs(). See Dave Smith's excellent analysis of this, particularly if you want the low-level details.

Second, lest anyone quibble on whether or not removable media access is otherwise part of the Android SDK, here is Dianne Hackborn's assessment:

> ...keep in mind: until Android 4.4, the official Android platform has not supported SD cards at all except for two special cases: the old school storage layout where external storage is an SD card (which is still supported by the platform today), and a small feature added to Android 3.0 where it would scan additional SD cards and add them to the media provider and give apps read-only access to their files (which is also still supported in the platform today). > > Android 4.4 is the first release of the platform that has actually allowed applications to use SD cards for storage. Any access to them prior to that was through private, unsupported APIs. We now have a quite rich API in the platform that allows applications to make use of SD cards in a supported way, in better ways than they have been able to before: they can make free use of their app-specific storage area without requiring any permissions in the app, and can access any other files on the SD card as long as they go through the file picker, again without needing any special permissions.

I came up with the following solution based on some answers found here.

CODE:

public class ExternalStorage {

	public static final String SD_CARD = "sdCard";
	public static final String EXTERNAL_SD_CARD = "externalSdCard";

	/**
	 * @return True if the external storage is available. False otherwise.
	 */
	public static boolean isAvailable() {
		String state = Environment.getExternalStorageState();
		if (Environment.MEDIA_MOUNTED.equals(state) || Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
			return true;
		}
		return false;
	}

	public static String getSdCardPath() {
		return Environment.getExternalStorageDirectory().getPath() + "/";
	}

	/**
	 * @return True if the external storage is writable. False otherwise.
	 */
	public static boolean isWritable() {
		String state = Environment.getExternalStorageState();
		if (Environment.MEDIA_MOUNTED.equals(state)) {
			return true;
		}
		return false;

	}

	/**
	 * @return A map of all storage locations available
	 */
	public static Map<String, File> getAllStorageLocations() {
		Map<String, File> map = new HashMap<String, File>(10);

		List<String> mMounts = new ArrayList<String>(10);
		List<String> mVold = new ArrayList<String>(10);
		mMounts.add("/mnt/sdcard");
		mVold.add("/mnt/sdcard");

		try {
			File mountFile = new File("/proc/mounts");
			if(mountFile.exists()){
				Scanner scanner = new Scanner(mountFile);
				while (scanner.hasNext()) {
					String line = scanner.nextLine();
					if (line.startsWith("/dev/block/vold/")) {
						String[] lineElements = line.split(" ");
						String element = lineElements[1];
	
						// don't add the default mount path
						// it's already in the list.
						if (!element.equals("/mnt/sdcard"))
							mMounts.add(element);
					}
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}

		try {
			File voldFile = new File("/system/etc/vold.fstab");
			if(voldFile.exists()){
				Scanner scanner = new Scanner(voldFile);
				while (scanner.hasNext()) {
					String line = scanner.nextLine();
					if (line.startsWith("dev_mount")) {
						String[] lineElements = line.split(" ");
						String element = lineElements[2];
	
						if (element.contains(":"))
							element = element.substring(0, element.indexOf(":"));
						if (!element.equals("/mnt/sdcard"))
							mVold.add(element);
					}
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		

		for (int i = 0; i < mMounts.size(); i++) {
			String mount = mMounts.get(i);
			if (!mVold.contains(mount))
				mMounts.remove(i--);
		}
		mVold.clear();
		
		List<String> mountHash = new ArrayList<String>(10);
		
		for(String mount : mMounts){
			File root = new File(mount);
			if (root.exists() && root.isDirectory() && root.canWrite()) {
				File[] list = root.listFiles();
				String hash = "[";
				if(list!=null){
					for(File f : list){
						hash += f.getName().hashCode()+":"+f.length()+", ";
					}
				}
				hash += "]";
				if(!mountHash.contains(hash)){
					String key = SD_CARD + "_" + map.size();
					if (map.size() == 0) {
						key = SD_CARD;
					} else if (map.size() == 1) {
						key = EXTERNAL_SD_CARD;
					}
					mountHash.add(hash);
					map.put(key, root);
				}
			}
		}

		mMounts.clear();
		
		if(map.isEmpty()){
				 map.put(SD_CARD, Environment.getExternalStorageDirectory());
		}
		return map;
	}
}

USAGE:

Map<String, File> externalLocations = ExternalStorage.getAllStorageLocations();
File sdCard = externalLocations.get(ExternalStorage.SD_CARD);
File externalSdCard = externalLocations.get(ExternalStorage.EXTERNAL_SD_CARD);

I had an application that used a ListPreference where the user was required to select the location of where they wanted to save something.

In that app, I scanned /proc/mounts and /system/etc/vold.fstab for sdcard mount points. I stored the mount points from each file into two separate ArrayLists.

Then, I compared one list with the other and discarded items that were not in both lists. That gave me a list of root paths to each sdcard.

From there, I tested the paths with File.exists(), File.isDirectory(), and File.canWrite(). If any of those tests were false, I discarded that path from the list.

Whatever was left in the list, I converted to a String[] array so it could be used by the ListPreference values attribute.

You can view the code here: http://sapienmobile.com/?p=204

You can try to use the support library function called of ContextCompat.getExternalFilesDirs() :

      final File[] appsDir=ContextCompat.getExternalFilesDirs(getActivity(),null);
      final ArrayList<File> extRootPaths=new ArrayList<>();
      for(final File file : appsDir)
        extRootPaths.add(file.getParentFile().getParentFile().getParentFile().getParentFile());

The first one is the primary external storage, and the rest are supposed to be real SD-cards paths.

The reason for the multiple ".getParentFile()" is to go up another folder, since the original path is

.../Android/data/YOUR_APP_PACKAGE_NAME/files/

---

EDIT: here's a more comprehensive way I've created, to get the sd-cards paths:

  /**
   * returns a list of all available sd cards paths, or null if not found.
   *
   * @param includePrimaryExternalStorage set to true if you wish to also include the path of the primary external storage
   */
  @TargetApi(Build.VERSION_CODES.HONEYCOMB)
  public static List<String> getSdCardPaths(final Context context, final boolean includePrimaryExternalStorage)
    {
    final File[] externalCacheDirs=ContextCompat.getExternalCacheDirs(context);
    if(externalCacheDirs==null||externalCacheDirs.length==0)
      return null;
    if(externalCacheDirs.length==1)
      {
      if(externalCacheDirs[0]==null)
        return null;
      final String storageState=EnvironmentCompat.getStorageState(externalCacheDirs[0]);
      if(!Environment.MEDIA_MOUNTED.equals(storageState))
        return null;
      if(!includePrimaryExternalStorage&&VERSION.SDK_INT>=VERSION_CODES.HONEYCOMB&&Environment.isExternalStorageEmulated())
        return null;
      }
    final List<String> result=new ArrayList<>();
    if(includePrimaryExternalStorage||externalCacheDirs.length==1)
      result.add(getRootOfInnerSdCardFolder(externalCacheDirs[0]));
    for(int i=1;i<externalCacheDirs.length;++i)
      {
      final File file=externalCacheDirs[i];
      if(file==null)
        continue;
      final String storageState=EnvironmentCompat.getStorageState(file);
      if(Environment.MEDIA_MOUNTED.equals(storageState))
        result.add(getRootOfInnerSdCardFolder(externalCacheDirs[i]));
      }
    if(result.isEmpty())
      return null;
    return result;
    }

  /** Given any file/folder inside an sd card, this will return the path of the sd card */
  private static String getRootOfInnerSdCardFolder(File file)
    {
    if(file==null)
      return null;
    final long totalSpace=file.getTotalSpace();
    while(true)
      {
      final File parentFile=file.getParentFile();
      if(parentFile==null||parentFile.getTotalSpace()!=totalSpace||!parentFile.canRead())
        return file.getAbsolutePath();
      file=parentFile;
      }
    }

---

Edit: better solution here:

https://stackoverflow.com/a/27197248/878126

In order to retrieve all the External Storages (whether they are SD cards or internal non-removable storages), you can use the following code:

final String state = Environment.getExternalStorageState();

if ( Environment.MEDIA_MOUNTED.equals(state) || Environment.MEDIA_MOUNTED_READ_ONLY.equals(state) ) {  // we can read the External Storage...           
	//Retrieve the primary External Storage:
	final File primaryExternalStorage = Environment.getExternalStorageDirectory();
	
	//Retrieve the External Storages root directory:
	final String externalStorageRootDir;
	if ( (externalStorageRootDir = primaryExternalStorage.getParent()) == null ) {  // no parent...
		Log.d(TAG, "External Storage: " + primaryExternalStorage + "\n");
	}
	else {
		final File externalStorageRoot = new File( externalStorageRootDir );
		final File[] files = externalStorageRoot.listFiles();

		for ( final File file : files ) {
			if ( file.isDirectory() && file.canRead() && (file.listFiles().length > 0) ) {  // it is a real directory (not a USB drive)...
				Log.d(TAG, "External Storage: " + file.getAbsolutePath() + "\n");
			}
		}
	}
}

Alternatively, you might use System.getenv("EXTERNAL_STORAGE") to retrieve the primary External Storage directory (e.g. "/storage/sdcard0") and System.getenv("SECONDARY_STORAGE") to retieve the list of all the secondary directories (e.g. "/storage/extSdCard:/storage/UsbDriveA:/storage/UsbDriveB"). Remember that, also in this case, you might want to filter the list of secondary directories in order to exclude the USB drives.

In any case, please note that using hard-coded paths is always a bad approach (expecially when every manufacturer may change it as pleased).

Like Richard I also use /proc/mounts file to get the list of available storage options

public class StorageUtils {

    private static final String TAG = "StorageUtils";

    public static class StorageInfo {

        public final String path;
        public final boolean internal;
        public final boolean readonly;
        public final int display_number;

        StorageInfo(String path, boolean internal, boolean readonly, int display_number) {
            this.path = path;
            this.internal = internal;
            this.readonly = readonly;
            this.display_number = display_number;
        }

        public String getDisplayName() {
            StringBuilder res = new StringBuilder();
            if (internal) {
                res.append("Internal SD card");
            } else if (display_number > 1) {
                res.append("SD card " + display_number);
            } else {
                res.append("SD card");
            }
            if (readonly) {
                res.append(" (Read only)");
            }
            return res.toString();
        }
    }

    public static List<StorageInfo> getStorageList() {

        List<StorageInfo> list = new ArrayList<StorageInfo>();
        String def_path = Environment.getExternalStorageDirectory().getPath();
        boolean def_path_internal = !Environment.isExternalStorageRemovable();
        String def_path_state = Environment.getExternalStorageState();
        boolean def_path_available = def_path_state.equals(Environment.MEDIA_MOUNTED)
                                    || def_path_state.equals(Environment.MEDIA_MOUNTED_READ_ONLY);
        boolean def_path_readonly = Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED_READ_ONLY);
        BufferedReader buf_reader = null;
        try {
            HashSet<String> paths = new HashSet<String>();
            buf_reader = new BufferedReader(new FileReader("/proc/mounts"));
            String line;
            int cur_display_number = 1;
            Log.d(TAG, "/proc/mounts");
            while ((line = buf_reader.readLine()) != null) {
                Log.d(TAG, line);
                if (line.contains("vfat") || line.contains("/mnt")) {
                    StringTokenizer tokens = new StringTokenizer(line, " ");
                    String unused = tokens.nextToken(); //device
                    String mount_point = tokens.nextToken(); //mount point
                    if (paths.contains(mount_point)) {
                        continue;
                    }
                    unused = tokens.nextToken(); //file system
                    List<String> flags = Arrays.asList(tokens.nextToken().split(",")); //flags
                    boolean readonly = flags.contains("ro");

                    if (mount_point.equals(def_path)) {
                        paths.add(def_path);
                        list.add(0, new StorageInfo(def_path, def_path_internal, readonly, -1));
                    } else if (line.contains("/dev/block/vold")) {
                        if (!line.contains("/mnt/secure")
                            && !line.contains("/mnt/asec")
                            && !line.contains("/mnt/obb")
                            && !line.contains("/dev/mapper")
                            && !line.contains("tmpfs")) {
                            paths.add(mount_point);
                            list.add(new StorageInfo(mount_point, false, readonly, cur_display_number++));
                        }
                    }
                }
            }

            if (!paths.contains(def_path) && def_path_available) {
                list.add(0, new StorageInfo(def_path, def_path_internal, def_path_readonly, -1));
            }

        } catch (FileNotFoundException ex) {
            ex.printStackTrace();
        } catch (IOException ex) {
            ex.printStackTrace();
        } finally {
            if (buf_reader != null) {
                try {
                    buf_reader.close();
                } catch (IOException ex) {}
            }
        }
        return list;
    }    
}

It is possible to find where any additional SD cards are mounted by reading /proc/mounts (standard Linux file) and cross-checking against vold data (/system/etc/vold.conf). And note, that the location returned by Environment.getExternalStorageDirectory() may not appear in vold configuration (in some devices it's internal storage that cannot be unmounted), but still has to be included in the list. However we didn't find a good way to describe them to the user.

I try all solutions inside this topic on this time. But all of them did not work correctly on devices with one external (removable) and one internal (not-removable) cards. Path of external card not possible get from 'mount' command, from 'proc/mounts' file etc.

And I create my own solution (on Paulo Luan's):

String sSDpath = null;
File   fileCur = null;
for( String sPathCur : Arrays.asList( "ext_card", "external_sd", "ext_sd", "external", "extSdCard",  "externalSdCard")) // external sdcard
{
   fileCur = new File( "/mnt/", sPathCur);
   if( fileCur.isDirectory() && fileCur.canWrite())
   {
  	 sSDpath = fileCur.getAbsolutePath();
  	 break;
   }
}
fileCur = null;
if( sSDpath == null)  sSDpath = Environment.getExternalStorageDirectory().getAbsolutePath();

If you look at the source code for android.os.Environment you will see that Android relies heavily on environment variables for paths. You can use the "SECONDARY_STORAGE" environment variable to find the path to the removable sd card.

/**
 * Get a file using an environmental variable.
 *
 * @param variableName
 *         The Environment variable name.
 * @param paths
 *         Any paths to the file if the Environment variable was not found.
 * @return the File or {@code null} if the File could not be located.
 */
private static File getDirectory(String variableName, String... paths) {
    String path = System.getenv(variableName);
    if (!TextUtils.isEmpty(path)) {
        if (path.contains(":")) {
            for (String _path : path.split(":")) {
                File file = new File(_path);
                if (file.exists()) {
                    return file;
                }
            }
        } else {
            File file = new File(path);
            if (file.exists()) {
                return file;
            }
        }
    }
    if (paths != null && paths.length > 0) {
        for (String _path : paths) {
            File file = new File(_path);
            if (file.exists()) {
                return file;
            }
        }
    }
    return null;
}

Example usage:

public static final File REMOVABLE_STORAGE = getDirectory("SECONDARY_STORAGE");

Just simply use this:

String primary_sd = System.getenv("EXTERNAL_STORAGE");
if(primary_sd != null)
	Log.i("EXTERNAL_STORAGE", primary_sd);
String secondary_sd = System.getenv("SECONDARY_STORAGE");
if(secondary_sd != null)
	Log.i("SECONDARY_STORAGE", secondary_sd)

> Is there an universal way to find the location of an external SD card?

By universal way, if you mean official way; yes there is one.

In API level 19 i.e. in Android version 4.4 Kitkat, they have added File[] getExternalFilesDirs (String type) in Context Class that allows apps to store data/files in micro SD cards.

Android 4.4 is the first release of the platform that has actually allowed apps to use SD cards for storage. Any access to SD cards before API level 19 was through private, unsupported APIs.

getExternalFilesDirs(String type) returns absolute paths to application-specific directories on all shared/external storage devices. It means, it will return paths to both internal and external memory. Generally, second returned path would be the storage path for microSD card (if any).

But note that,

> Shared storage may not always be available, since removable media can > be ejected by the user. Media state can be checked using > getExternalStorageState(File). > > There is no security enforced with these files. For example, any > application holding WRITE_EXTERNAL_STORAGE can write to these files.

The Internal and External Storage terminology according to Google/official Android docs is quite different from what we think.

Here is the way I use to find the external card. Use mount cmd return then parse the vfat part.

String s = "";
try {
Process process = new ProcessBuilder().command("mount")
		.redirectErrorStream(true).start();

process.waitFor();

InputStream is = process.getInputStream();
byte[] buffer = new byte[1024];
while (is.read(buffer) != -1) {
	s = s + new String(buffer);
}
is.close();
} catch (Exception e) {
e.printStackTrace();
}

//用行分隔mount列表
String[] lines = s.split("\n");
for(int i=0; i<lines.length; i++) {
//如果行内有挂载路径且为vfat类型，说明可能是内置或者外置sd的挂载点
if(-1 != lines[i].indexOf(path[0]) && -1 != lines[i].indexOf("vfat")) {
	//再用空格分隔
	String[] blocks = lines[i].split("\\s");
	for(int j=0; j<blocks.length; j++) {
		//判断是否是挂载为vfat类型
		if(-1 != blocks[j].indexOf(path[0])) {
			//Test if it is the external sd card.
		}
	}
}
}

This solution handles the fact that System.getenv("SECONDARY_STORAGE") is of no use with Marshmallow.

Tested and working on:

• Samsung Galaxy Tab 2 (Android 4.1.1 - Stock)

• Samsung Galaxy Note 8.0 (Android 4.2.2 - Stock)

• Samsung Galaxy S4 (Android 4.4 - Stock)

• Samsung Galaxy S4 (Android 5.1.1 - Cyanogenmod)

• Samsung Galaxy Tab A (Android 6.0.1 - Stock)

    /**
     * Returns all available external SD-Card roots in the system.
     *
     * @return paths to all available external SD-Card roots in the system.
     */
    public static String[] getStorageDirectories() {
        String [] storageDirectories;
        String rawSecondaryStoragesStr = System.getenv("SECONDARY_STORAGE");
  
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            List<String> results = new ArrayList<String>();
            File[] externalDirs = applicationContext.getExternalFilesDirs(null);
            for (File file : externalDirs) {
                String path = file.getPath().split("/Android")[0];
                if((Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && Environment.isExternalStorageRemovable(file))
                        || rawSecondaryStoragesStr != null && rawSecondaryStoragesStr.contains(path)){
                    results.add(path);
                }
            }
            storageDirectories = results.toArray(new String[0]);
        }else{
            final Set<String> rv = new HashSet<String>();
  
            if (!TextUtils.isEmpty(rawSecondaryStoragesStr)) {
                final String[] rawSecondaryStorages = rawSecondaryStoragesStr.split(File.pathSeparator);
                Collections.addAll(rv, rawSecondaryStorages);
            }
            storageDirectories = rv.toArray(new String[rv.size()]);
        }
        return storageDirectories;
    }
  

Since my original answer above, scanning vold is no longer viable across the various manufacturers.

I've developed a more reliable and straight forward method.

File mnt = new File("/storage");
if (!mnt.exists())
    mnt = new File("/mnt");

File[] roots = mnt.listFiles(new FileFilter() {

    @Override
    public boolean accept(File pathname) {
	    return pathname.isDirectory() && pathname.exists()
			    && pathname.canWrite() && !pathname.isHidden()
			    && !isSymlink(pathname);
    }
});

roots will contain all the writeable root directories on the system, including any usb connected usb devices.

NOTE: The canWrite method needs the android.permission.WRITE_EXTERNAL_STORAGE permission.

Here is the method I use to find a removable SD card. It's complex, and probably overkill for some situations, but it works on a wide variety of Android versions and device manufacturers that I've tested over the last few years. I don't know of any devices since API level 15 on which it doesn't find the SD card, if there is one mounted. It won't return false positives in most cases, especially if you give it the name of a known file to look for.

Please let me know if you run into any cases where it doesn't work.

import android.content.Context;
import android.os.Build;
import android.os.Environment;
import android.support.v4.content.ContextCompat;
import android.text.TextUtils;
import android.util.Log;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Locale;
import java.util.regex.Pattern;

public class SDCard {
    private static final String TAG = "SDCard";

    /** In some scenarios we can expect to find a specified file or folder on SD cards designed
     * to work with this app. If so, set KNOWNFILE to that filename. It will make our job easier.
     * Set it to null otherwise. */
    private static final String KNOWNFILE = null;

    /** Common paths for microSD card. **/
    private static String[] commonPaths = {
            // Some of these taken from
            // https://stackoverflow.com/questions/13976982/removable-storage-external-sdcard-path-by-manufacturers
            // These are roughly in order such that the earlier ones, if they exist, are more sure
            // to be removable storage than the later ones.
            "/mnt/Removable/MicroSD",
            "/storage/removable/sdcard1", // !< Sony Xperia Z1
            "/Removable/MicroSD", // Asus ZenPad C
            "/removable/microsd",
            "/external_sd", // Samsung
            "/_ExternalSD", // some LGs
            "/storage/extSdCard", // later Samsung
            "/storage/extsdcard", // Main filesystem is case-sensitive; FAT isn't.
            "/mnt/extsd", // some Chinese tablets, e.g. Zeki
            "/storage/sdcard1", // If this exists it's more likely than sdcard0 to be removable.
            "/mnt/extSdCard",
            "/mnt/sdcard/external_sd",
            "/mnt/external_sd",
            "/storage/external_SD",
            "/storage/ext_sd", // HTC One Max
            "/mnt/sdcard/_ExternalSD",
            "/mnt/sdcard-ext",

            "/sdcard2", // HTC One M8s
            "/sdcard1", // Sony Xperia Z
            "/mnt/media_rw/sdcard1",   // 4.4.2 on CyanogenMod S3
            "/mnt/sdcard", // This can be built-in storage (non-removable).
            "/sdcard",
            "/storage/sdcard0",
            "/emmc",
            "/mnt/emmc",
            "/sdcard/sd",
            "/mnt/sdcard/bpemmctest",
            "/mnt/external1",
            "/data/sdext4",
            "/data/sdext3",
            "/data/sdext2",
            "/data/sdext",
            "/storage/microsd" //ASUS ZenFone 2

            // If we ever decide to support USB OTG storage, the following paths could be helpful:
            // An LG Nexus 5 apparently uses usb://1002/UsbStorage/ as a URI to access an SD
            // card over OTG cable. Other models, like Galaxy S5, use /storage/UsbDriveA
            //        "/mnt/usb_storage",
            //        "/mnt/UsbDriveA",
            //        "/mnt/UsbDriveB",
    };

    /** Find path to removable SD card. */
    public static File findSdCardPath(Context context) {
        String[] mountFields;
        BufferedReader bufferedReader = null;
        String lineRead = null;

        /** Possible SD card paths */
        LinkedHashSet<File> candidatePaths = new LinkedHashSet<>();

        /** Build a list of candidate paths, roughly in order of preference. That way if
         * we can't definitively detect removable storage, we at least can pick a more likely
         * candidate. */

        // Could do: use getExternalStorageState(File path), with and without an argument, when
        // available. With an argument is available since API level 21.
        // This may not be necessary, since we also check whether a directory exists and has contents,
        // which would fail if the external storage state is neither MOUNTED nor MOUNTED_READ_ONLY.

        // I moved hard-coded paths toward the end, but we need to make sure we put the ones in
        // backwards order that are returned by the OS. And make sure the iterators respect
        // the order!
        // This is because when multiple "external" storage paths are returned, it's always (in
        // experience, but not guaranteed by documentation) with internal/emulated storage
        // first, removable storage second.

        // Add value of environment variables as candidates, if set:
        // EXTERNAL_STORAGE, SECONDARY_STORAGE, EXTERNAL_SDCARD_STORAGE
        // But note they are *not* necessarily *removable* storage! Especially EXTERNAL_STORAGE.
        // And they are not documented (API) features. Typically useful only for old versions of Android.

        String val = System.getenv("SECONDARY_STORAGE");
        if (!TextUtils.isEmpty(val)) addPath(val, null, candidatePaths);
        val = System.getenv("EXTERNAL_SDCARD_STORAGE");
        if (!TextUtils.isEmpty(val)) addPath(val, null, candidatePaths);

        // Get listing of mounted devices with their properties.
        ArrayList<File> mountedPaths = new ArrayList<>();
        try {
            // Note: Despite restricting some access to /proc (http://stackoverflow.com/a/38728738/423105),
            // Android 7.0 does *not* block access to /proc/mounts, according to our test on George's Alcatel A30 GSM.
            bufferedReader = new BufferedReader(new FileReader("/proc/mounts"));

            // Iterate over each line of the mounts listing.
            while ((lineRead = bufferedReader.readLine()) != null) {
                Log.d(TAG, "\nMounts line: " + lineRead);
                mountFields = lineRead.split(" ");

                // columns: device, mountpoint, fs type, options... Example:
                // /dev/block/vold/179:97 /storage/sdcard1 vfat rw,dirsync,nosuid,nodev,noexec,relatime,uid=1000,gid=1015,fmask=0002,dmask=0002,allow_utime=0020,codepage=cp437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro 0 0
                String device = mountFields[0], path = mountFields[1], fsType = mountFields[2];

                // The device, path, and fs type must conform to expected patterns.
                if (!(devicePattern.matcher(device).matches() &&
                        pathPattern.matcher(path).matches() &&
                        fsTypePattern.matcher(fsType).matches()) ||
                        // mtdblock is internal, I'm told.
                        device.contains("mtdblock") ||
                        // Check for disqualifying patterns in the path.
                        pathAntiPattern.matcher(path).matches()) {
                    // If this mounts line fails our tests, skip it.
                    continue;
                }

                // TODO maybe: check options to make sure it's mounted RW?
                // The answer at http://stackoverflow.com/a/13648873/423105 does.
                // But it hasn't seemed to be necessary so far in my testing.

                // This line met the criteria so far, so add it to candidate list.
                addPath(path, null, mountedPaths);
            }
        } catch (IOException ignored) {
        } finally {
            if (bufferedReader != null) {
                try {
                    bufferedReader.close();
                } catch (IOException ignored) {
                }
            }
        }

        // Append the paths from mount table to candidate list, in reverse order.
        if (!mountedPaths.isEmpty()) {
            // See https://stackoverflow.com/a/5374346/423105 on why the following is necessary.
            // Basically, .toArray() needs its parameter to know what type of array to return.
            File[] mountedPathsArray = mountedPaths.toArray(new File[mountedPaths.size()]);
            addAncestors(candidatePaths, mountedPathsArray);
        }

        // Add hard-coded known common paths to candidate list:
        addStrings(candidatePaths, commonPaths);

        // If the above doesn't work we could try the following other options, but in my experience they
        // haven't added anything helpful yet.

        // getExternalFilesDir() and getExternalStorageDirectory() typically something app-specific like
        //   /storage/sdcard1/Android/data/com.mybackuparchives.android/files
        // so we want the great-great-grandparent folder.

        // This may be non-removable.
        Log.d(TAG, "Environment.getExternalStorageDirectory():");
        addPath(null, ancestor(Environment.getExternalStorageDirectory()), candidatePaths);

        // Context.getExternalFilesDirs() is only available from API level 19. You can use
        // ContextCompat.getExternalFilesDirs() on earlier APIs, but it only returns one dir anyway.
        Log.d(TAG, "context.getExternalFilesDir(null):");
        addPath(null, ancestor(context.getExternalFilesDir(null)), candidatePaths);

        // "Returns absolute paths to application-specific directories on all external storage
        // devices where the application can place persistent files it owns."
        // We might be able to use these to deduce a higher-level folder that isn't app-specific.
        // Also, we apparently have to call getExternalFilesDir[s](), at least in KITKAT+, in order to ensure that the
        // "external files" directory exists and is available.
        Log.d(TAG, "ContextCompat.getExternalFilesDirs(context, null):");
        addAncestors(candidatePaths, ContextCompat.getExternalFilesDirs(context, null));
        // Very similar results:
        Log.d(TAG, "ContextCompat.getExternalCacheDirs(context):");
        addAncestors(candidatePaths, ContextCompat.getExternalCacheDirs(context));

        // TODO maybe: use getExternalStorageState(File path), with and without an argument, when
        // available. With an argument is available since API level 21.
        // This may not be necessary, since we also check whether a directory exists,
        // which would fail if the external storage state is neither MOUNTED nor MOUNTED_READ_ONLY.

        // A "public" external storage directory. But in my experience it doesn't add anything helpful.
        // Note that you can't pass null, or you'll get an NPE.
        final File publicDirectory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MUSIC);
        // Take the parent, because we tend to get a path like /pathTo/sdCard/Music.
        addPath(null, publicDirectory.getParentFile(), candidatePaths);
        // EXTERNAL_STORAGE: may not be removable.
        val = System.getenv("EXTERNAL_STORAGE");
        if (!TextUtils.isEmpty(val)) addPath(val, null, candidatePaths);

        if (candidatePaths.isEmpty()) {
            Log.w(TAG, "No removable microSD card found.");
            return null;
        } else {
            Log.i(TAG, "\nFound potential removable storage locations: " + candidatePaths);
        }

        // Accept or eliminate candidate paths if we can determine whether they're removable storage.
        // In Lollipop and later, we can check isExternalStorageRemovable() status on each candidate.
        if (Build.VERSION.SDK_INT >= 21) {
            Iterator<File> itf = candidatePaths.iterator();
            while (itf.hasNext()) {
                File dir = itf.next();
                // handle illegalArgumentException if the path is not a valid storage device.
                try {
                    if (Environment.isExternalStorageRemovable(dir)
                        // && containsKnownFile(dir)
                            ) {
                        Log.i(TAG, dir.getPath() + " is removable external storage");
                        return dir;
                    } else if (Environment.isExternalStorageEmulated(dir)) {
                        Log.d(TAG, "Removing emulated external storage dir " + dir);
                        itf.remove();
                    }
                } catch (IllegalArgumentException e) {
                    Log.d(TAG, "isRemovable(" + dir.getPath() + "): not a valid storage device.", e);
                }
            }
        }

        // Continue trying to accept or eliminate candidate paths based on whether they're removable storage.
        // On pre-Lollipop, we only have singular externalStorage. Check whether it's removable.
        if (Build.VERSION.SDK_INT >= 9) {
            File externalStorage = Environment.getExternalStorageDirectory();
            Log.d(TAG, String.format(Locale.ROOT, "findSDCardPath: getExternalStorageDirectory = %s", externalStorage.getPath()));
            if (Environment.isExternalStorageRemovable()) {
                // Make sure this is a candidate.
                // TODO: Does this contains() work? Should we be canonicalizing paths before comparing?
                if (candidatePaths.contains(externalStorage)
                    // && containsKnownFile(externalStorage)
                        ) {
                    Log.d(TAG, "Using externalStorage dir " + externalStorage);
                    return externalStorage;
                }
            } else if (Build.VERSION.SDK_INT >= 11 && Environment.isExternalStorageEmulated()) {
                Log.d(TAG, "Removing emulated external storage dir " + externalStorage);
                candidatePaths.remove(externalStorage);
            }
        }

        // If any directory contains our special test file, consider that the microSD card.
        if (KNOWNFILE != null) {
            for (File dir : candidatePaths) {
                Log.d(TAG, String.format(Locale.ROOT, "findSdCardPath: Looking for known file in candidate path, %s", dir));
                if (containsKnownFile(dir)) return dir;
            }
        }

        // If we don't find the known file, still try taking the first candidate.
        if (!candidatePaths.isEmpty()) {
            Log.d(TAG, "No definitive path to SD card; taking the first realistic candidate.");
            return candidatePaths.iterator().next();
        }

        // If no reasonable path was found, give up.
        return null;
    }

    /** Add each path to the collection. */
    private static void addStrings(LinkedHashSet<File> candidatePaths, String[] newPaths) {
        for (String path : newPaths) {
            addPath(path, null, candidatePaths);
        }
    }

    /** Add ancestor of each File to the collection. */
    private static void addAncestors(LinkedHashSet<File> candidatePaths, File[] files) {
        for (int i = files.length - 1; i >= 0; i--) {
            addPath(null, ancestor(files[i]), candidatePaths);
        }
    }

    /**
     * Add a new candidate directory path to our list, if it's not obviously wrong.
     * Supply path as either String or File object.
     * @param strNew path of directory to add (or null)
     * @param fileNew directory to add (or null)
     */
    private static void addPath(String strNew, File fileNew, Collection<File> paths) {
        // If one of the arguments is null, fill it in from the other.
        if (strNew == null) {
            if (fileNew == null) return;
            strNew = fileNew.getPath();
        } else if (fileNew == null) {
            fileNew = new File(strNew);
        }

        if (!paths.contains(fileNew) &&
                // Check for paths known not to be removable SD card.
                // The antipattern check can be redundant, depending on where this is called from.
                !pathAntiPattern.matcher(strNew).matches()) {

            // Eliminate candidate if not a directory or not fully accessible.
            if (fileNew.exists() && fileNew.isDirectory() && fileNew.canExecute()) {
                Log.d(TAG, "  Adding candidate path " + strNew);
                paths.add(fileNew);
            } else {
                Log.d(TAG, String.format(Locale.ROOT, "  Invalid path %s: exists: %b isDir: %b canExec: %b canRead: %b",
                        strNew, fileNew.exists(), fileNew.isDirectory(), fileNew.canExecute(), fileNew.canRead()));
            }
        }
    }

    private static final String ANDROID_DIR = File.separator + "Android";

    private static File ancestor(File dir) {
        // getExternalFilesDir() and getExternalStorageDirectory() typically something app-specific like
        //   /storage/sdcard1/Android/data/com.mybackuparchives.android/files
        // so we want the great-great-grandparent folder.
        if (dir == null) {
            return null;
        } else {
            String path = dir.getAbsolutePath();
            int i = path.indexOf(ANDROID_DIR);
            if (i == -1) {
                return dir;
            } else {
                return new File(path.substring(0, i));
            }
        }
    }

    /** Returns true iff dir contains the special test file.
     * Assumes that dir exists and is a directory. (Is this a necessary assumption?) */
    private static boolean containsKnownFile(File dir) {
        if (KNOWNFILE == null) return false;

        File knownFile = new File(dir, KNOWNFILE);
        return knownFile.exists();
    }

    private static Pattern
            /** Pattern that SD card device should match */
            devicePattern = Pattern.compile("/dev/(block/.*vold.*|fuse)|/mnt/.*"),
    /** Pattern that SD card mount path should match */
    pathPattern = Pattern.compile("/(mnt|storage|external_sd|extsd|_ExternalSD|Removable|.*MicroSD).*",
            Pattern.CASE_INSENSITIVE),
    /** Pattern that the mount path should not match.
     * 'emulated' indicates an internal storage location, so skip it.
     * 'asec' is an encrypted package file, decrypted and mounted as a directory. */
    pathAntiPattern = Pattern.compile(".*(/secure|/asec|/emulated).*"),
    /** These are expected fs types, including vfat. tmpfs is not OK.
     * fuse can be removable SD card (as on Moto E or Asus ZenPad), or can be internal (Huawei G610). */
    fsTypePattern = Pattern.compile(".*(fat|msdos|ntfs|ext[34]|fuse|sdcard|esdfs).*");
}

P.S.

• Don't forget <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" /> in the manifest. And at API level 23 and higher, make sure to use checkSelfPermission / requestPermissions.
• Set KNOWNFILE="myappfile" if there's a file or folder you expect to find on the SD card. That makes detection more accurate.
• Obviously you'll want to cache the value of findSdCardPath(), rather than recomputing it every time you need it.
• There's a bunch of logging (Log.d()) in the above code. It helps diagnose any cases where the right path isn't found. Comment it out if you don't want logging.

it been so late but finally i got something i have tested most of devices( by manufacturer and android versions) its working on Android 2.2+. if you find it is not working, comment it with your device name. i will fix it. if anyone interested i will explain how it works.

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FilenameFilter;
import java.io.IOException;
import java.io.InputStreamReader;

import android.util.Log;


/**
 * @author ajeet
 *05-Dec-2014  2014
 *
 */
public class StorageUtil {
 
	public boolean isRemovebleSDCardMounted() {
		File file = new File("/sys/class/block/");
		File[] files = file.listFiles(new MmcblkFilter("mmcblk\\d$"));
		boolean flag = false;
		for (File mmcfile : files) {
			File scrfile = new File(mmcfile, "device/scr");
			if (scrfile.exists()) {
				flag = true;
				break;
			}
		}
		return flag;
	}

	public String getRemovebleSDCardPath() throws IOException {
		String sdpath = null;
		File file = new File("/sys/class/block/");
		File[] files = file.listFiles(new MmcblkFilter("mmcblk\\d$"));
		String sdcardDevfile = null;
		for (File mmcfile : files) {
			Log.d("SDCARD", mmcfile.getAbsolutePath());
			File scrfile = new File(mmcfile, "device/scr");
			if (scrfile.exists()) {
				sdcardDevfile = mmcfile.getName();
				Log.d("SDCARD", mmcfile.getName());
				break;
			}
		}
		if (sdcardDevfile == null) {
			return null;
		}
		FileInputStream is;
		BufferedReader reader;

		files = file.listFiles(new MmcblkFilter(sdcardDevfile + "p\\d+"));
		String deviceName = null;
		if (files.length > 0) {
			Log.d("SDCARD", files[0].getAbsolutePath());
			File devfile = new File(files[0], "dev");
			if (devfile.exists()) {
				FileInputStream fis = new FileInputStream(devfile);
				reader = new BufferedReader(new InputStreamReader(fis));
				String line = reader.readLine();
				deviceName = line;
			}
			Log.d("SDCARD", "" + deviceName);
			if (deviceName == null) {
				return null;
			}
			Log.d("SDCARD", deviceName);

			final File mountFile = new File("/proc/self/mountinfo");

			if (mountFile.exists()) {
				is = new FileInputStream(mountFile);
				reader = new BufferedReader(new InputStreamReader(is));
				String line = null;
				while ((line = reader.readLine()) != null) {
					// Log.d("SDCARD", line);
					// line = reader.readLine();
					// Log.d("SDCARD", line);
					String[] mPonts = line.split("\\s+");
					if (mPonts.length > 6) {
						if (mPonts[2].trim().equalsIgnoreCase(deviceName)) {
							if (mPonts[4].contains(".android_secure")
									|| mPonts[4].contains("asec")) {
								continue;
							}
							sdpath = mPonts[4];
							Log.d("SDCARD", mPonts[4]);

						}
					}

				}
			}

		}

		return sdpath;
	}

	static class MmcblkFilter implements FilenameFilter {
		private String pattern;

		public MmcblkFilter(String pattern) {
			this.pattern = pattern;

		}

		@Override
		public boolean accept(File dir, String filename) {
			if (filename.matches(pattern)) {
				return true;
			}
			return false;
		}

	}

}

The only working solution I found was this one that uses reflection

 /**
 * Get external sd card path using reflection
 * @param mContext
 * @param is_removable is external storage removable
 * @return
 */
private static String getExternalStoragePath(Context mContext, boolean is_removable) {

    StorageManager mStorageManager = (StorageManager) mContext.getSystemService(Context.STORAGE_SERVICE);
    Class<?> storageVolumeClazz = null;
    try {
        storageVolumeClazz = Class.forName("android.os.storage.StorageVolume");
        Method getVolumeList = mStorageManager.getClass().getMethod("getVolumeList");
        Method getPath = storageVolumeClazz.getMethod("getPath");
        Method isRemovable = storageVolumeClazz.getMethod("isRemovable");
        Object result = getVolumeList.invoke(mStorageManager);
        final int length = Array.getLength(result);
        for (int i = 0; i < length; i++) {
            Object storageVolumeElement = Array.get(result, i);
            String path = (String) getPath.invoke(storageVolumeElement);
            boolean removable = (Boolean) isRemovable.invoke(storageVolumeElement);
            if (is_removable == removable) {
                return path;
            }
        }
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    }
    return null;
}

Google had blocked many options to get the external sd card path and add permissions levels to protect the sd card directory from the app's garbage. Every solution I had tried didn't supply a sufficient way to get the external and removable sd card path.

After that said, Google did supply a way to get the external paths that the app can write to it and check if it is removable or not.

With this simple API, you can get the path to the removable external directory and with the right write/read permissions.

File[] files = getExternalFilesDirs(null);
for(File file : files){
    if(Environment.isExternalStorageRemovable(file)){
        return file;
    }
}

I don't know why but I need to call .createNewFile() on a File created in the public storage directories before using it. In the framework the comments for that method say it isn't useful. Here's a sample...

String myPath = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PODCASTS) + File.separator + "My Directory";
final File myDir = new File(myPath);
try {
myDir.mkdirs();
} catch (Exception ex) {
Toast.makeText(this, "error: " + ex.getMessage(), Toast.LENGTH_LONG).show();
}



        String fname = "whatever";
        File newFile = new File(myDir, fname);

        Log.i(TAG, "File exists --> " + newFile.exists()) //will be false  
    try {
            if (newFile.createNewFile()) {

                 //continue 

              } else {
            
                Log.e(TAG, "error creating file");
                
            }
            
        } catch (Exception e) {
            Log.e(TAG, e.toString());
        }

I have created a utils method to check a SD card is available on device or not, and get SD card path on device if it available.

You can copy 2 methods bellow into your project's class that you need. That's all.

public String isRemovableSDCardAvailable() {
	final String FLAG = "mnt";
	final String SECONDARY_STORAGE = System.getenv("SECONDARY_STORAGE");
	final String EXTERNAL_STORAGE_DOCOMO = System.getenv("EXTERNAL_STORAGE_DOCOMO");
	final String EXTERNAL_SDCARD_STORAGE = System.getenv("EXTERNAL_SDCARD_STORAGE");
	final String EXTERNAL_SD_STORAGE = System.getenv("EXTERNAL_SD_STORAGE");
	final String EXTERNAL_STORAGE = System.getenv("EXTERNAL_STORAGE");

	Map<Integer, String> listEnvironmentVariableStoreSDCardRootDirectory = new HashMap<Integer, String>();
	listEnvironmentVariableStoreSDCardRootDirectory.put(0, SECONDARY_STORAGE);
	listEnvironmentVariableStoreSDCardRootDirectory.put(1, EXTERNAL_STORAGE_DOCOMO);
	listEnvironmentVariableStoreSDCardRootDirectory.put(2, EXTERNAL_SDCARD_STORAGE);
	listEnvironmentVariableStoreSDCardRootDirectory.put(3, EXTERNAL_SD_STORAGE);
	listEnvironmentVariableStoreSDCardRootDirectory.put(4, EXTERNAL_STORAGE);

	File externalStorageList[] = null;
	if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.KITKAT) {
		externalStorageList = getContext().getExternalFilesDirs(null);
	}
	String directory = null;
	int size = listEnvironmentVariableStoreSDCardRootDirectory.size();
	for (int i = 0; i < size; i++) {
		if (externalStorageList != null && externalStorageList.length > 1 && externalStorageList[1] != null)
			directory = externalStorageList[1].getAbsolutePath();
		else
			directory = listEnvironmentVariableStoreSDCardRootDirectory.get(i);

		directory = canCreateFile(directory);
		if (directory != null && directory.length() != 0) {
			if (i == size - 1) {
				if (directory.contains(FLAG)) {
					Log.e(getClass().getSimpleName(), "SD Card's directory: " + directory);
					return directory;
				} else {
					return null;
				}
			}
			Log.e(getClass().getSimpleName(), "SD Card's directory: " + directory);
			return directory;
		}
	}
	return null;
}

/**
 * Check if can create file on given directory. Use this enclose with method
 * {@link BeginScreenFragement#isRemovableSDCardAvailable()} to check sd
 * card is available on device or not.
 * 
 * @param directory
 * @return
 */
public String canCreateFile(String directory) {
	final String FILE_DIR = directory + File.separator + "hoang.txt";
	File tempFlie = null;
	try {
		tempFlie = new File(FILE_DIR);
		FileOutputStream fos = new FileOutputStream(tempFlie);
		fos.write(new byte[1024]);
		fos.flush();
		fos.close();
		Log.e(getClass().getSimpleName(), "Can write file on this directory: " + FILE_DIR);
	} catch (Exception e) {
		Log.e(getClass().getSimpleName(), "Write file error: " + e.getMessage());
		return null;
	} finally {
		if (tempFlie != null && tempFlie.exists() && tempFlie.isFile()) {
			// tempFlie.delete();
			tempFlie = null;
		}
	}
	return directory;
}

By writing below code you will get the location:

/storage/663D-554E/Android/data/app_package_name/files/

which stores your app data at /android/data location inside the sd_card.

File[] list = ContextCompat.getExternalFilesDirs(MainActivity.this, null);

list[1]+"/fol" 

> for getting location pass 0 for internal and 1 for sdcard to file array.

I have tested this code on a moto g4 plus and Samsung device (all works fine).

hope this might helpful.

Its work for all external devices, But make sure only get external device folder name and then you need to get file from given location using File class.

public static List<String> getExternalMounts() {
		final List<String> out = new ArrayList<>();
		String reg = "(?i).*vold.*(vfat|ntfs|exfat|fat32|ext3|ext4).*rw.*";
		String s = "";
		try {
			final Process process = new ProcessBuilder().command("mount")
					.redirectErrorStream(true).start();
			process.waitFor();
			final InputStream is = process.getInputStream();
			final byte[] buffer = new byte[1024];
			while (is.read(buffer) != -1) {
				s = s + new String(buffer);
			}
			is.close();
		} catch (final Exception e) {
			e.printStackTrace();
		}

		// parse output
		final String[] lines = s.split("\n");
		for (String line : lines) {
			if (!line.toLowerCase(Locale.US).contains("asec")) {
				if (line.matches(reg)) {
					String[] parts = line.split(" ");
					for (String part : parts) {
						if (part.startsWith("/"))
							if (!part.toLowerCase(Locale.US).contains("vold"))
								out.add(part);
					}
				}
			}
		}
		return out;
	}

Calling:

List<String> list=getExternalMounts();
		if(list.size()>0)
		{
			String[] arr=list.get(0).split("/");
			int size=0;
			if(arr!=null && arr.length>0) {
				size= arr.length - 1;
			}
			File parentDir=new File("/storage/"+arr[size]);
			if(parentDir.listFiles()!=null){
				File parent[] = parentDir.listFiles();

				for (int i = 0; i < parent.length; i++) {

					// get file path as parent[i].getAbsolutePath());

				}
			}
		}

Getting access to external storage

In order to read or write files on the external storage, your app must acquire the READ_EXTERNAL_STORAGE or WRITE_EXTERNAL_STORAGE system permissions. For example:

<manifest ...>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    ...
</manifest>

/sdcard => Internal Storage (It's a symlink but should work)

/mnt/extSdCard => External Sdcard

This is for Samsung Galaxy S3

You can probably bank on this being true for most...double check however!