X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/0368e13ebc5a5cfef0c69124cae34301a6d890ff..b526df9ab5269735bce42af3ed9fbe777e513093:/crunch_scripts/crunchutil/subst.py

diff --git a/crunch_scripts/crunchutil/subst.py b/crunch_scripts/crunchutil/subst.py
index ff3486354f..bd99d3c71c 100644
--- a/crunch_scripts/crunchutil/subst.py
+++ b/crunch_scripts/crunchutil/subst.py
@@ -1,5 +1,9 @@
-import os
 import glob
+import os
+import re
+import stat
+
+BACKSLASH_ESCAPE_RE = re.compile(r'\\(.)')
 
 class SubstitutionError(Exception):
     pass
@@ -35,13 +39,23 @@ def search(c):
     return None
 
 def sub_file(v):
-    return os.path.join(os.environ['TASK_KEEPMOUNT'], v)
+    path = os.path.join(os.environ['TASK_KEEPMOUNT'], v)
+    st = os.stat(path)
+    if st and stat.S_ISREG(st.st_mode):
+        return path
+    else:
+        raise SubstitutionError("$(file {}) is not accessible or is not a regular file".format(path))
 
 def sub_dir(v):
     d = os.path.dirname(v)
     if d == '':
         d = v
-    return os.path.join(os.environ['TASK_KEEPMOUNT'], d)
+    path = os.path.join(os.environ['TASK_KEEPMOUNT'], d)
+    st = os.stat(path)
+    if st and stat.S_ISDIR(st.st_mode):
+        return path
+    else:
+        raise SubstitutionError("$(dir {}) is not accessible or is not a directory".format(path))
 
 def sub_basename(v):
     return os.path.splitext(os.path.basename(v))[0]
@@ -49,7 +63,7 @@ def sub_basename(v):
 def sub_glob(v):
     l = glob.glob(v)
     if len(l) == 0:
-        raise SubstitutionError("$(glob): No match on '%s'" % v)
+        raise SubstitutionError("$(glob {}) no match found".format(v))
     else:
         return l[0]
 
@@ -62,7 +76,7 @@ def do_substitution(p, c, subs=default_subs):
     while True:
         m = search(c)
         if m is None:
-            return c
+            return BACKSLASH_ESCAPE_RE.sub(r'\1', c)
 
         v = do_substitution(p, c[m[0]+2 : m[1]])
         var = True