[pallets#1470,pallets#1476] Use subprocess instead of os.system

click/_compat.py

@@ -258,6 +258,18 @@ def filename_to_ui(value):
         if isinstance(value, bytes):
             value = value.decode(get_filesystem_encoding(), 'replace')
         return value
+
+    def which(cmd):
+        with open(os.devnull, 'w') as devnull:
+            p = subprocess.Popen(
+                ['which', cmd],
+                stdout=subprocess.PIPE,
+                stderr=devnull,
+            )
+            if p.wait() == 0:
+                return p.stdout.strip()
+            else:
+                return None
 else:
     text_type = str
     raw_input = input
@@ -461,6 +473,8 @@ def filename_to_ui(value):
                 .decode('utf-8', 'replace')
         return value
 
+    from shutil import which
+
 
 def get_streerror(e, default=None):
     if hasattr(e, 'strerror'):

click/_termui_impl.py

@@ -18,7 +18,7 @@
 import contextlib
 from ._compat import _default_text_stdout, range_type, isatty, \
      open_stream, strip_ansi, term_len, get_best_encoding, WIN, int_types, \
-     CYGWIN
+     CYGWIN, which
 from .utils import echo
 from .exceptions import ClickException
 
@@ -333,15 +333,15 @@ def pager(generator, color=None):
     if os.environ.get('TERM') in ('dumb', 'emacs'):
         return _nullpager(stdout, generator, color)
     if WIN or sys.platform.startswith('os2'):
-        return _tempfilepager(generator, 'more <', color)
-    if hasattr(os, 'system') and os.system('(less) 2>/dev/null') == 0:
+        return _pipetempfilepager(generator, 'more', color)
+    if which('less') is not None:
         return _pipepager(generator, 'less', color)
 
     import tempfile
     fd, filename = tempfile.mkstemp()
     os.close(fd)
     try:
-        if hasattr(os, 'system') and os.system('more "%s"' % filename) == 0:
+        if which('more') is not None:
             return _pipepager(generator, 'more', color)
         return _nullpager(stdout, generator, color)
     finally:
@@ -399,6 +399,31 @@ def _pipepager(generator, cmd, color):
 
 def _tempfilepager(generator, cmd, color):
     """Page through text by invoking a program on a temporary file."""
+    import subprocess
+    import tempfile
+    filename = tempfile.mktemp()
+    # TODO: This never terminates if the passed generator never terminates.
+    text = "".join(generator)
+    if not color:
+        text = strip_ansi(text)
+    encoding = get_best_encoding(sys.stdout)
+    with open_stream(filename, 'wb')[0] as f:
+        f.write(text.encode(encoding))
+    try:
+        subprocess.call([cmd, filename])
+    except OSError:
+        # Command not found
+        pass
+    finally:
+        os.unlink(filename)
+
+
+def _pipetempfilepager(generator, cmd, color):
+    """
+    Page through text by invoking a program with a temporary file redirected
+    as input.
+    """
+    import subprocess
     import tempfile
     filename = tempfile.mktemp()
     # TODO: This never terminates if the passed generator never terminates.
@@ -409,7 +434,11 @@ def _tempfilepager(generator, cmd, color):
     with open_stream(filename, 'wb')[0] as f:
         f.write(text.encode(encoding))
     try:
-        os.system(cmd + ' "' + filename + '"')
+        with open_stream(filename, 'rb')[0] as f:
+            subprocess.call([cmd], stdin=f)
+    except OSError:
+        # Command not found
+        pass
     finally:
         os.unlink(filename)
 
@@ -441,7 +470,7 @@ def get_editor(self):
         if WIN:
             return 'notepad'
         for editor in 'sensible-editor', 'vim', 'nano':
-            if os.system('which %s >/dev/null 2>&1' % editor) == 0:
+            if which(editor) is not None:
                 return editor
         return 'vi'
 
@@ -532,20 +561,32 @@ def _unquote_file(url):
     elif WIN:
         if locate:
             url = _unquote_file(url)
-            args = 'explorer /select,"%s"' % _unquote_file(
-                url.replace('"', ''))
+            args = ['explorer', '/select,%s' % _unquote_file(url)]
         else:
-            args = 'start %s "" "%s"' % (
-                wait and '/WAIT' or '', url.replace('"', ''))
-        return os.system(args)
+            args = ['start']
+            if wait:
+                args.append('/WAIT')
+            args.append('')
+            args.append(url)
+        try:
+            return subprocess.call(args)
+        except OSError:
+            # Command not found
+            return 127
     elif CYGWIN:
         if locate:
             url = _unquote_file(url)
-            args = 'cygstart "%s"' % (os.path.dirname(url).replace('"', ''))
+            args = ['cygstart', os.path.dirname(url)]
         else:
-            args = 'cygstart %s "%s"' % (
-                wait and '-w' or '', url.replace('"', ''))
-        return os.system(args)
+            args = ['cygstart']
+            if wait:
+                args.append('-w')
+            args.append(url)
+        try:
+            return subprocess.call(args)
+        except OSError:
+            # Command not found
+            return 127
 
     try:
         if locate:

click/termui.py

@@ -390,10 +390,15 @@ def clear():
     if not isatty(sys.stdout):
         return
     # If we're on Windows and we don't have colorama available, then we
-    # clear the screen by shelling out.  Otherwise we can use an escape
+    # clear the screen by invoking `cls`.  Otherwise we can use an escape
     # sequence.
     if WIN:
-        os.system('cls')
+        import subprocess
+        try:
+            subprocess.call(['cls'])
+        except OSError:
+            # Command not found
+            pass
     else:
         sys.stdout.write('\033[2J\033[1;1H')
 

tests/test_imports.py

@@ -32,7 +32,7 @@ def tracking_import(module, locals=None, globals=None, fromlist=None,
 ALLOWED_IMPORTS = set([
     'weakref', 'os', 'struct', 'collections', 'sys', 'contextlib',
     'functools', 'stat', 're', 'codecs', 'inspect', 'itertools', 'io',
-    'threading', 'colorama', 'errno', 'fcntl', 'datetime'
+    'threading', 'colorama', 'errno', 'fcntl', 'datetime', 'shutil'
 ])
 
 if WIN: