diff --git a/user/grind.c b/user/grind.c
index d11b20b..85899f5 100644
--- a/user/grind.c
+++ b/user/grind.c
@@ -57,7 +57,7 @@ go(int which_child)
 
   mkdir("grindir");
   if(chdir("grindir") != 0){
-    printf("chdir grindir failed\n");
+    printf("grind: chdir grindir failed\n");
     exit(1);
   }
   chdir("/");
@@ -75,7 +75,7 @@ go(int which_child)
       unlink("grindir/../a");
     } else if(what == 4){
       if(chdir("grindir") != 0){
-        printf("chdir grindir failed\n");
+        printf("grind: chdir grindir failed\n");
         exit(1);
       }
       unlink("../b");
@@ -139,7 +139,7 @@ go(int which_child)
         exit(1);
       }
       if(chdir("../grindir/..") != 0){
-        printf("chdir failed\n");
+        printf("grind: chdir failed\n");
         exit(1);
       }
       kill(pid);
@@ -188,7 +188,7 @@ go(int which_child)
         unlink("x");
         exit(0);
       } else if(pid < 0){
-        printf("fork failed\n");
+        printf("grind: fork failed\n");
         exit(1);
       }
       wait(0);
@@ -198,24 +198,24 @@ go(int which_child)
       // file descriptors, blocks.
       int fd1 = open("c", O_CREATE|O_RDWR);
       if(fd1 < 0){
-        printf("create c failed\n");
+        printf("grind: create c failed\n");
         exit(1);
       }
       if(write(fd1, "x", 1) != 1){
-        printf("write c failed\n");
+        printf("grind: write c failed\n");
         exit(1);
       }
       struct stat st;
       if(fstat(fd1, &st) != 0){
-        printf("fstat failed\n");
+        printf("grind: fstat failed\n");
         exit(1);
       }
       if(st.size != 1){
-        printf("fstat reports wrong size %d\n", (int)st.size);
+        printf("grind: fstat reports wrong size %d\n", (int)st.size);
         exit(1);
       }
       if(st.ino > 200){
-        printf("fstat reports crazy i-number %d\n", st.ino);
+        printf("grind: fstat reports crazy i-number %d\n", st.ino);
         exit(1);
       }
       close(fd1);
@@ -224,11 +224,11 @@ go(int which_child)
       // echo hi | cat
       int aa[2], bb[2];
       if(pipe(aa) < 0){
-        fprintf(2, "pipe failed\n");
+        fprintf(2, "grind: pipe failed\n");
         exit(1);
       }
       if(pipe(bb) < 0){
-        fprintf(2, "pipe failed\n");
+        fprintf(2, "grind: pipe failed\n");
         exit(1);
       }
       int pid1 = fork();
@@ -238,16 +238,16 @@ go(int which_child)
         close(aa[0]);
         close(1);
         if(dup(aa[1]) != 1){
-          fprintf(2, "dup failed\n");
+          fprintf(2, "grind: dup failed\n");
           exit(1);
         }
         close(aa[1]);
         char *args[3] = { "echo", "hi", 0 };
         exec("grindir/../echo", args);
-        fprintf(2, "echo: not found\n");
+        fprintf(2, "grind: echo: not found\n");
         exit(2);
       } else if(pid1 < 0){
-        fprintf(2, "fork failed\n");
+        fprintf(2, "grind: fork failed\n");
         exit(3);
       }
       int pid2 = fork();
@@ -256,22 +256,22 @@ go(int which_child)
         close(bb[0]);
         close(0);
         if(dup(aa[0]) != 0){
-          fprintf(2, "dup failed\n");
+          fprintf(2, "grind: dup failed\n");
           exit(4);
         }
         close(aa[0]);
         close(1);
         if(dup(bb[1]) != 1){
-          fprintf(2, "dup failed\n");
+          fprintf(2, "grind: dup failed\n");
           exit(5);
         }
         close(bb[1]);
         char *args[2] = { "cat", 0 };
         exec("/cat", args);
-        fprintf(2, "cat: not found\n");
+        fprintf(2, "grind: cat: not found\n");
         exit(6);
       } else if(pid2 < 0){
-        fprintf(2, "fork failed\n");
+        fprintf(2, "grind: fork failed\n");
         exit(7);
       }
       close(aa[0]);
@@ -285,7 +285,7 @@ go(int which_child)
       wait(&st1);
       wait(&st2);
       if(st1 != 0 || st2 != 0 || strcmp(buf, "hi") != 0){
-        printf("exec pipeline failed %d %d \"%s\"\n", st1, st2, buf);
+        printf("grind: exec pipeline failed %d %d \"%s\"\n", st1, st2, buf);
         exit(1);
       }
     }