util: T2226: improve popen, cmd and add run

improves open and cmd adds a new help function run.

the extra optional arguments provide all the features of
subprocess used by every module of VyOS.

popen matches closely subprocess.Popen
cmd   matches closely subprocess.check_output
run   matches closely subprocess.call and os.system

popen returns the string and errord code
cmd   returns the string and raise on error
      (the class can be defined the default is OSError)
run   returns the return code of the command

the options are:
   shell=None, the code auto-detect is a shell is required

   decode=None, use .decode() otherwise the encoding will be used
   env=None, universal_newlines=None: as per subprocess.Popen

   input=None, timeout=None, stdout=PIPE, stderr=STDOUT,
   as per Popen.communicate

1 files changed, 52 insertions, 15 deletions

diff --git a/python/vyos/util.py b/python/vyos/util.py
index c8ab43c11..f63ed057e 100644
--- a/python/vyos/util.py
+++ b/python/vyos/util.py
@@ -16,7 +16,7 @@
 import os
 import re
 import sys
-from subprocess import Popen, PIPE, STDOUT
+from subprocess import Popen, PIPE, STDOUT, DEVNULL
 
 
 # debugging
@@ -33,29 +33,63 @@ def debug_msg(message, section=''):
 
 #  commands
 
-
-def popen(command, section=''):
-    p = Popen(command, stdout=PIPE, stderr=STDOUT, shell=True)
-    tmp = p.communicate()[0].strip()
+# popen does not raise
+# it returns the output of the command and the error code
+def popen(command, section='', shell=None, input=None, timeout=None, env=None, universal_newlines=None, stdout=PIPE, stderr=STDOUT, decode=None):
+    use_shell = shell
+    if shell is None:
+        use_shell = True if ' ' in command else False
+    p = Popen(
+        command,
+        stdout=stdout, stderr=stderr,
+        env=env, shell=use_shell,
+        universal_newlines=universal_newlines,
+    )
+    tmp = p.communicate(input, timeout)[0].strip()
     debug_msg(f"cmd '{command}'", section)
-    decoded = tmp.decode()
+    decoded = tmp.decode(decode) if decode else tmp.decode()
     if decoded:
         debug_msg(f"returned:\n{decoded}", section)
     return decoded, p.returncode
 
-
-def cmd(command, section=''):
-    decoded, code = popen(command, section)
+# run does not raise
+# it returns the error code
+def run(command, section='', shell=None, input=None, timeout=None, env=None, universal_newlines=None, stdout=PIPE, stderr=STDOUT, decode=None):
+    _, code = popen(
+        command, section,
+        stdout=stdout, stderr=stderr,
+        input=input, timeout=timeout,
+        env=env, shell=shell,
+        universal_newlines=universal_newlines,
+        decode=decode,
+    )
+    return code
+
+# cmd does raise
+# it returns the output
+def cmd(command, section='', shell=None, input=None, timeout=None, env=None, universal_newlines=None, stdout=PIPE, stderr=STDOUT, decode=None, raising=None, message=''):
+    decoded, code = popen(
+        command, section,
+        stdout=stdout, stderr=stderr,
+        input=input, timeout=timeout,
+        env=env, shell=shell,
+        universal_newlines=universal_newlines,
+        decode=decode,
+    )
     if code != 0:
-        # error code can be recovered with .errno
-        raise OSError(code, f'{command}\nreturned: {decoded}')
+        feedback = message + '\n' if message else ''
+        feedback += f'failed to run command: {command}\n'
+        feedback += f'returned: {decoded}\n'
+        feedback += f'exit code: {code}'
+        if raising is None:
+            # error code can be recovered with .errno
+            raise OSError(code, feedback)
+        else:
+            raise raising(feedback)
     return decoded
 
 
-# file manipulation
-
-
-
+# This is now deprecated
 def subprocess_cmd(command):
     """ execute arbitrary command via Popen """
     from subprocess import Popen, PIPE
@@ -63,6 +97,9 @@ def subprocess_cmd(command):
     p.communicate()
 
 
+# file manipulation
+
+
 def read_file(path):
     """ Read a file to string """
     with open(path, 'r') as f: