diff --git a/LiveDiag/LDAppDelegate.m b/LiveDiag/LDAppDelegate.m
index 43775b1..b5aef78 100644
--- a/LiveDiag/LDAppDelegate.m
+++ b/LiveDiag/LDAppDelegate.m
@@ -14,7 +14,7 @@ @implementation LDAppDelegate
 - (void)applicationDidFinishLaunching:(NSNotification *)aNotification
 {
     //check path settings, any commands
-    if([LDUtils pathTo:@"blockdiag"] == nil || [LDUtils pathTo:@"seqdiag"] == nil || [LDUtils pathTo:@"actdiag"] == nil || [LDUtils pathTo:@"nwdiag"] == nil || [LDUtils pathTo:@"rackdiag"] == nil) {
+    if (![LDUtils checkPaths]) {
         NSAlert *alert = [NSAlert alertWithMessageText:@"Path Setting" defaultButton:@"OK" alternateButton:@"Cancel" otherButton:nil informativeTextWithFormat:@"Please specify a path to blockdiag and the other."];
         if ([alert runModal] == NSAlertDefaultReturn) {
             LDAppDelegate *delegate = (LDAppDelegate *)[[NSApplication sharedApplication] delegate];
diff --git a/LiveDiag/Library/LDUtils.h b/LiveDiag/Library/LDUtils.h
index 7e52b21..57e83b6 100644
--- a/LiveDiag/Library/LDUtils.h
+++ b/LiveDiag/Library/LDUtils.h
@@ -10,6 +10,7 @@
 
 @interface LDUtils : NSObject
 
++ (BOOL)checkPaths;
 + (NSString *)pathTo:(NSString *)command;
 
 @end
diff --git a/LiveDiag/Library/LDUtils.m b/LiveDiag/Library/LDUtils.m
index 9d2ac03..2fafc72 100644
--- a/LiveDiag/Library/LDUtils.m
+++ b/LiveDiag/Library/LDUtils.m
@@ -10,9 +10,65 @@
 
 @implementation LDUtils
 
++ (BOOL)checkPaths {
+    __block NSArray *commands = @[@"blockdiag", @"seqdiag", @"actdiag", @"nwdiag", @"rackdiag"];
+
+    BOOL (^validatePaths)() = ^BOOL() {
+        __block BOOL r;
+        [commands enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
+            NSString *path = [LDUtils pathTo:obj];
+            r = (path != nil && ![path isEqualToString:@""]);
+            *stop = !r;
+        }];
+        return r;
+    };
+
+    BOOL result = validatePaths();
+    if (!result) {
+        [commands enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
+            NSString *path = [LDUtils pathTo:obj];
+            if (path == nil || [path isEqualToString:@""]) {
+                [LDUtils setPathWithCommand:obj];
+            }
+        }];
+        result = validatePaths();
+    }
+    return result;
+}
+
 + (NSString *)pathTo:(NSString *)command {
     NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
     return [userDefaults stringForKey:[NSString stringWithFormat:@"path_%@", command]];
 }
 
++ (NSString *)setPathWithCommand:(NSString *)command {
+    NSTask *task = [[NSTask alloc] init];
+    NSPipe *pipe = [NSPipe pipe];
+
+    [task setStandardOutput:pipe];
+    [task setCurrentDirectoryPath:[[NSBundle mainBundle].bundlePath stringByDeletingLastPathComponent]];
+    [task setLaunchPath:@"/bin/bash"];
+
+    NSString *run = [NSString stringWithFormat:@"which %@", command];
+    NSArray *args = [NSArray arrayWithObjects:@"-l", @"-c", run, nil];
+    [task setArguments:args];
+    [task launch];
+    [task waitUntilExit];
+
+    if ([task terminationStatus] != 0) {
+        // Exit if not exists.
+        return nil;
+    }
+
+    NSData *data = pipe.fileHandleForReading.availableData;
+    NSString *path = [NSString stringWithFormat:@"%s", data.bytes];
+    NSArray *paths = [path componentsSeparatedByString:@"\n"];
+    if (paths.count > 0) {
+        path = paths.firstObject;
+    }
+    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
+    [userDefaults setValue:path forKey:[NSString stringWithFormat:@"path_%@", command]];
+    return path;
+}
+
 @end