How do I call get twice in a row in Python? - python-2.x

I'm trying to get a Python script to append two different prefixes to a command that come from two different environment variables. Currently the script is only configured to accept different prefixes from ONE variable, and is stubbornly resisting my attempts to make it take two variables.
The code looks like this:
proc = subprocess.Popen([subst.get('TOOLCHAIN_PREFIX','') + 'readelf', '-d', lib], stdout = subprocess.PIPE)
If I just replace TOOLCHAIN_PREFIX with GNU_PREFIX, which is the other environment variable I want, the code works as-is. But if I try to do something like...
proc = subprocess.Popen([subst.get('TOOLCHAIN_PREFIX','') + subst.get('GNU_PREFIX','') + 'readelf', '-d', lib], stdout = subprocess.PIPE)
It doesn't work. In fact, Python seems to be stubbornly not allowing me to call "get" twice, or to combine the two flags.
What I want is to make it take both these variables as input and tack them onto the front of the command in order. Fixing the Makefiles was easy, but this Python script is like Greek to me. So for instance, I want something where this..
TOOLCHAIN_PREFIX = "s"
GNU_PREFIX = "g"
Can produce a command like this:
sgreadelf -d
And if either one isn't set, it's just omitted.
TOOLCHAIN_PREFIX = "s"
GNU_PREFIX = ""
Should produce:
sreadelf -d
TOOLCHAIN_PREFIX = ""
GNU_PREFIX = "g"
greadelf -d
It's very frustrating and the code seems to be very stubborn about only letting me pull in one environment variable. If I add the other variable as an argument, it says too many arguments. If I add it as a second command, it doesn't like that either.
Is there really just no way to pull in two environment variables and append both of them to the beginning of a string? It seems like it should be simple, but they seem bent on not letting me do it easily without reading an entire book on Python.
EDIT: Sorry, I forgot to mention where "subst" comes from. I thought it was a builtin command, but apparently it's defined elsewhere. I know next to nothing about Python.
config = buildObject.from_environment()
for var in ('topsrcdir', 'topobjdir', 'defines', 'non_global_defines',
'substs'):
value = getattr(config, var)
setattr(sys.modules[__name__], var, value)
substs = dict(substs)
for var in os.environ:
if var not in ('CPP', 'CXXCPP', 'SHELL') and var in substs:
substs[var] = os.environ[var]
And here is the error:
File "/export/home/jeremy/Downloads/git/Solaris-UXP/toolkit/library/dependentlibs.py", line 55
proc = subprocess.Popen([substs.get(('TOOLCHAIN_PREFIX', '') + ('GNU_PREFIX', '') + 'readelf', '-d', lib], stdout = subprocess.PIPE)
^
SyntaxError: invalid syntax
This time I tried it without subst.get, but it gives the exact same error whether I put subst.get in front of the second argument or not. It's like it just won't let me put anything else on that command line.
EDIT2: I've been messing with the code and trying various things to get it to work, sorry it wasn't the exact same error I reported the first time. Here's two other things I tried and the error output messages.
File "/export/home/jeremy/Downloads/git/Solaris-UXP/toolkit/library/dependentlibs.py", line 55, in dependentlibs_readelf
proc = subprocess.Popen([substs.get(('TOOLCHAIN_PREFIX', '') + ('GNU_PREFIX', '')) + 'readelf', '-d', lib], stdout = subprocess.PIPE)
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
File "/export/home/jeremy/Downloads/git/Solaris-UXP/toolkit/library/dependentlibs.py", line 55, in dependentlibs_readelf
proc = subprocess.Popen([substs.get('TOOLCHAIN_PREFIX', '') + substs.get('GNU_PREFIX', '') + 'readelf', '-d', lib], stdout = subprocess.PIPE)
File "/usr/lib/python2.7/subprocess.py", line 394, in __init__
errread, errwrite)
File "/usr/lib/python2.7/subprocess.py", line 1047, in _execute_child
raise child_exception
OSError: [Errno 2] No such file or directory
EDIT3: I can't fit the entire output of printing 'substs' here, and it reveals more about what I'm working on than I really wanted to share originally, but basically it's about 60,000 characters of this:
{'MOZ_PERMISSIONS': '1', 'ANDROID_ANIMATED_VECTOR_DRAWABLE_AAR_LIB': '', 'X_LIBS': ' -L/usr/lib -R/usr/lib', 'CAIRO_FT_CFLAGS': ['-I/usr/include/freetype2', '-I/usr/include/libpng16', '-I/usr/include/harfbuzz', '-I/usr/include/glib-2.0', '-I/usr/lib/glib-2.0/include', '-I/usr/include/pcre', '-I/usr/include/freetype2', '-I/usr/include/libpng16', '-I/usr/include/harfbuzz', '-I/usr/include/glib-2.0', '-I/usr/lib/glib-2.0/include', '-I/usr/include/pcre'], 'MOZ_WIDGET_TOOLKIT': 'gtk2', 'MOZ_JPEG_LIBS': [], 'MOZ_ANDROID_MIN_SDK_VERSION': '', 'prefix': '/usr/local', 'TK_CFLAGS': ['-I/export/home/athenian/Downloads/git/Solaris-UXP/widget/gtk/compat', '-D_REENTRANT', '-D_PTHREADS', '-D_REENTRANT', '-D_POSIX_PTHREAD_SEMANTICS', '-I/usr/include/gtk-2.0', '-I/usr/include/gtk-unix-print-2.0', '-I/usr/include/gtk-2.0', '-I/usr/include/atk-1.0', '-I/usr/include/gtk-2.0', '-I/usr/lib/gtk-2.0/include', '-I/usr/include/pango-1.0', '-I/usr/include/fribidi', '-I/usr/include/gio-unix-2.0/', '-I/usr/include/gdk-pixbuf-2.0', '-I/usr/include/libpng16', '-I/usr/include/cairo', '-I/usr/include/pixman-1', '-I/usr/include/freetype2', '-I/usr/include/harfbuzz', '-I/usr/include/glib-2.0', '-I/usr/lib/glib-2.0/include', '-I/usr/include/pcre', '-I/usr/include/drm', '-I/usr/include/libpng16'], 'CPP': ['/usr/bin/gcc', '-E', '-std=gnu99'], 'MOZ_ALLOW_HEAP_EXECUTE_FLAGS': [], 'SSSE3_FLAGS': ['-mssse3'], 'MOZ_APP_BASENAME': 'Palemoon', 'AR_EXTRACT': '$(AR) x', 'mandir': '${prefix}/man', 'MOZ_APP_ANDROID_VERSION_CODE': '', 'ANDROID_PLAY_SERVICES_ADS_AAR': '', 'MOZILLA_VERSION': '4.4.0', 'TAR': '/usr/bin/gtar', 'MOZ_SYSTEM_JPEG': '', 'build_alias': 'i386-pc-solaris2.11', 'XLDFLAGS': ['-L/usr/lib', '-R/usr/lib'], 'STRIP': 'strip', 'MOZ_VPX_ERROR_CONCEALMENT': '', 'ZLIB_IN_MOZGLUE': '', 'CAIRO_TEE_CFLAGS': [], 'localstatedir': '${prefix}/var', 'ANDROID_SDK_ROOT': '', 'ANDROID_SUPPORT_V4_AAR': '', 'CLANG_CL': '', 'NONASCII': '', 'BUILD_ARM_NEON': '', 'build_vendor': 'pc', 'MOZ_FFVPX': '', 'VPX_ASFLAGS': ['-DPIC'], 'MOZ_APP_ID': '{8de7fcbb-c55c-4fbe-bfc5-fc555c87dbc4}', 'ANDROID_DESIGN_AAR': '', 'AAPT': '', 'MOZ_PNG_CFLAGS': [], 'MOZ_CAIRO_OSLIBS': ['-L/usr/lib', '-R/usr/lib', '-lXrender'], 'HAVE_TOOLCHAIN_SUPPORT_MSSE4_1': '1', 'AUTOCONF': '/usr/bin/autoconf-2.13', 'CLANG_LDFLAGS': '', 'RELEASE_OR_BETA': '1', 'WIN_UCRT_REDIST_DIR': '', 'HOST_LDFLAGS': '', 'VISIBILITY_FLAGS': ['-I/export/home/athenian/Downloads/git/Solaris-UXP/obj-release/dist/system_wrappers', '-include', '/export/home/athenian/Downloads/git/Solaris-UXP/config/gcc_hidden.h'], 'MOZILLA_UAVERSION': '4.4', 'MOZ_ASAN': '', 'MOZ_APP_UA_NAME': '', 'MOZ_STARTUP_NOTIFICATION_LIBS': [], 'LIBOBJS': '', 'MOZ_ENABLE_DWRITE_FONT': '', 'MOZ_GNOMEUI_LIBS': [], 'MOZ_COMPONENTS_VERSION_SCRIPT_LDFLAGS': '', 'MKSHLIB': '$(CXX) $(CXXFLAGS) $(DSO_PIC_CFLAGS) $(DSO_LDOPTS) -Wl,-h,$(DSO_SONAME) -o $#', 'MOZ_JPEG_CFLAGS': [], 'JS_POSIX_NSPR': '', 'host_cpu': 'i386', 'XCFLAGS': [], 'NSS_EXTRA_SYMBOLS_FILE': '', 'ICU_DATA_FILE': 'icudt58l.dat', 'DSO_LDOPTS': '-shared', 'ANDROID_PLAY_SERVICES_MEASUREMENT_AAR': '', 'PROFILE_USE_CFLAGS': '-fprofile-use
The rest is here, if you need it:
https://pastebin.com/cQr0AUTW

I managed to find a solution to this. It seems like the substrs.get command works in a very specific way that involves using keys and dictionaries, and everything you do with it has to be plugged in a certain way. It seems like it's extremely inflexible about how you invoke it for whatever reason.
This is the code that finally worked for me in this specific situation, it involved something called os.getenv. It is a bit weird-looking because I don't call both prefixes in the same way like I do in the Makefiles, but it effectively does what I want. I thought about changing TOOLCHAIN_PREFIX to match and use the same method, but I had weird issues with that as well. For some reason, this just works and it's good enough for my purposes.
proc = subprocess.Popen([substs.get('TOOLCHAIN_PREFIX','') + os.getenv('GNU_PREFIX') + 'readelf', '-d', lib], stdout = subprocess.PIPE)

Related

Bash Script - Not collateral after echo due to new line [duplicate]

I want to write a function that will execute a shell command and return its output as a string, no matter, is it an error or success message. I just want to get the same result that I would have gotten with the command line.
What would be a code example that would do such a thing?
For example:
def run_command(cmd):
# ??????
print run_command('mysqladmin create test -uroot -pmysqladmin12')
# Should output something like:
# mysqladmin: CREATE DATABASE failed; error: 'Can't create database 'test'; database exists'
In all officially maintained versions of Python, the simplest approach is to use the subprocess.check_output function:
>>> subprocess.check_output(['ls', '-l'])
b'total 0\n-rw-r--r-- 1 memyself staff 0 Mar 14 11:04 files\n'
check_output runs a single program that takes only arguments as input.1 It returns the result exactly as printed to stdout. If you need to write input to stdin, skip ahead to the run or Popen sections. If you want to execute complex shell commands, see the note on shell=True at the end of this answer.
The check_output function works in all officially maintained versions of Python. But for more recent versions, a more flexible approach is available.
Modern versions of Python (3.5 or higher): run
If you're using Python 3.5+, and do not need backwards compatibility, the new run function is recommended by the official documentation for most tasks. It provides a very general, high-level API for the subprocess module. To capture the output of a program, pass the subprocess.PIPE flag to the stdout keyword argument. Then access the stdout attribute of the returned CompletedProcess object:
>>> import subprocess
>>> result = subprocess.run(['ls', '-l'], stdout=subprocess.PIPE)
>>> result.stdout
b'total 0\n-rw-r--r-- 1 memyself staff 0 Mar 14 11:04 files\n'
The return value is a bytes object, so if you want a proper string, you'll need to decode it. Assuming the called process returns a UTF-8-encoded string:
>>> result.stdout.decode('utf-8')
'total 0\n-rw-r--r-- 1 memyself staff 0 Mar 14 11:04 files\n'
This can all be compressed to a one-liner if desired:
>>> subprocess.run(['ls', '-l'], stdout=subprocess.PIPE).stdout.decode('utf-8')
'total 0\n-rw-r--r-- 1 memyself staff 0 Mar 14 11:04 files\n'
If you want to pass input to the process's stdin, you can pass a bytes object to the input keyword argument:
>>> cmd = ['awk', 'length($0) > 5']
>>> ip = 'foo\nfoofoo\n'.encode('utf-8')
>>> result = subprocess.run(cmd, stdout=subprocess.PIPE, input=ip)
>>> result.stdout.decode('utf-8')
'foofoo\n'
You can capture errors by passing stderr=subprocess.PIPE (capture to result.stderr) or stderr=subprocess.STDOUT (capture to result.stdout along with regular output). If you want run to throw an exception when the process returns a nonzero exit code, you can pass check=True. (Or you can check the returncode attribute of result above.) When security is not a concern, you can also run more complex shell commands by passing shell=True as described at the end of this answer.
Later versions of Python streamline the above further. In Python 3.7+, the above one-liner can be spelled like this:
>>> subprocess.run(['ls', '-l'], capture_output=True, text=True).stdout
'total 0\n-rw-r--r-- 1 memyself staff 0 Mar 14 11:04 files\n'
Using run this way adds just a bit of complexity, compared to the old way of doing things. But now you can do almost anything you need to do with the run function alone.
Older versions of Python (3-3.4): more about check_output
If you are using an older version of Python, or need modest backwards compatibility, you can use the check_output function as briefly described above. It has been available since Python 2.7.
subprocess.check_output(*popenargs, **kwargs)
It takes takes the same arguments as Popen (see below), and returns a string containing the program's output. The beginning of this answer has a more detailed usage example. In Python 3.5+, check_output is equivalent to executing run with check=True and stdout=PIPE, and returning just the stdout attribute.
You can pass stderr=subprocess.STDOUT to ensure that error messages are included in the returned output. When security is not a concern, you can also run more complex shell commands by passing shell=True as described at the end of this answer.
If you need to pipe from stderr or pass input to the process, check_output won't be up to the task. See the Popen examples below in that case.
Complex applications and legacy versions of Python (2.6 and below): Popen
If you need deep backwards compatibility, or if you need more sophisticated functionality than check_output or run provide, you'll have to work directly with Popen objects, which encapsulate the low-level API for subprocesses.
The Popen constructor accepts either a single command without arguments, or a list containing a command as its first item, followed by any number of arguments, each as a separate item in the list. shlex.split can help parse strings into appropriately formatted lists. Popen objects also accept a host of different arguments for process IO management and low-level configuration.
To send input and capture output, communicate is almost always the preferred method. As in:
output = subprocess.Popen(["mycmd", "myarg"],
stdout=subprocess.PIPE).communicate()[0]
Or
>>> import subprocess
>>> p = subprocess.Popen(['ls', '-a'], stdout=subprocess.PIPE,
... stderr=subprocess.PIPE)
>>> out, err = p.communicate()
>>> print out
.
..
foo
If you set stdin=PIPE, communicate also allows you to pass data to the process via stdin:
>>> cmd = ['awk', 'length($0) > 5']
>>> p = subprocess.Popen(cmd, stdout=subprocess.PIPE,
... stderr=subprocess.PIPE,
... stdin=subprocess.PIPE)
>>> out, err = p.communicate('foo\nfoofoo\n')
>>> print out
foofoo
Note Aaron Hall's answer, which indicates that on some systems, you may need to set stdout, stderr, and stdin all to PIPE (or DEVNULL) to get communicate to work at all.
In some rare cases, you may need complex, real-time output capturing. Vartec's answer suggests a way forward, but methods other than communicate are prone to deadlocks if not used carefully.
As with all the above functions, when security is not a concern, you can run more complex shell commands by passing shell=True.
Notes
1. Running shell commands: the shell=True argument
Normally, each call to run, check_output, or the Popen constructor executes a single program. That means no fancy bash-style pipes. If you want to run complex shell commands, you can pass shell=True, which all three functions support. For example:
>>> subprocess.check_output('cat books/* | wc', shell=True, text=True)
' 1299377 17005208 101299376\n'
However, doing this raises security concerns. If you're doing anything more than light scripting, you might be better off calling each process separately, and passing the output from each as an input to the next, via
run(cmd, [stdout=etc...], input=other_output)
Or
Popen(cmd, [stdout=etc...]).communicate(other_output)
The temptation to directly connect pipes is strong; resist it. Otherwise, you'll likely see deadlocks or have to do hacky things like this.
This is way easier, but only works on Unix (including Cygwin) and Python2.7.
import commands
print commands.getstatusoutput('wc -l file')
It returns a tuple with the (return_value, output).
For a solution that works in both Python2 and Python3, use the subprocess module instead:
from subprocess import Popen, PIPE
output = Popen(["date"],stdout=PIPE)
response = output.communicate()
print response
I had the same problem but figured out a very simple way of doing this:
import subprocess
output = subprocess.getoutput("ls -l")
print(output)
Note: This solution is Python3 specific as subprocess.getoutput() doesn't work in Python2
Something like that:
def runProcess(exe):
p = subprocess.Popen(exe, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
while(True):
# returns None while subprocess is running
retcode = p.poll()
line = p.stdout.readline()
yield line
if retcode is not None:
break
Note, that I'm redirecting stderr to stdout, it might not be exactly what you want, but I want error messages also.
This function yields line by line as they come (normally you'd have to wait for subprocess to finish to get the output as a whole).
For your case the usage would be:
for line in runProcess('mysqladmin create test -uroot -pmysqladmin12'.split()):
print line,
This is a tricky but super simple solution which works in many situations:
import os
os.system('sample_cmd > tmp')
print(open('tmp', 'r').read())
A temporary file(here is tmp) is created with the output of the command and you can read from it your desired output.
Extra note from the comments:
You can remove the tmp file in the case of one-time job. If you need to do this several times, there is no need to delete the tmp.
os.remove('tmp')
Vartec's answer doesn't read all lines, so I made a version that did:
def run_command(command):
p = subprocess.Popen(command,
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT)
return iter(p.stdout.readline, b'')
Usage is the same as the accepted answer:
command = 'mysqladmin create test -uroot -pmysqladmin12'.split()
for line in run_command(command):
print(line)
You can use following commands to run any shell command. I have used them on ubuntu.
import os
os.popen('your command here').read()
Note: This is deprecated since python 2.6. Now you must use subprocess.Popen. Below is the example
import subprocess
p = subprocess.Popen("Your command", shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()[0]
print p.split("\n")
I had a slightly different flavor of the same problem with the following requirements:
Capture and return STDOUT messages as they accumulate in the STDOUT buffer (i.e. in realtime).
#vartec solved this Pythonically with his use of generators and the 'yield'
keyword above
Print all STDOUT lines (even if process exits before STDOUT buffer can be fully read)
Don't waste CPU cycles polling the process at high-frequency
Check the return code of the subprocess
Print STDERR (separate from STDOUT) if we get a non-zero error return code.
I've combined and tweaked previous answers to come up with the following:
import subprocess
from time import sleep
def run_command(command):
p = subprocess.Popen(command,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
shell=True)
# Read stdout from subprocess until the buffer is empty !
for line in iter(p.stdout.readline, b''):
if line: # Don't print blank lines
yield line
# This ensures the process has completed, AND sets the 'returncode' attr
while p.poll() is None:
sleep(.1) #Don't waste CPU-cycles
# Empty STDERR buffer
err = p.stderr.read()
if p.returncode != 0:
# The run_command() function is responsible for logging STDERR
print("Error: " + str(err))
This code would be executed the same as previous answers:
for line in run_command(cmd):
print(line)
Your Mileage May Vary, I attempted #senderle's spin on Vartec's solution in Windows on Python 2.6.5, but I was getting errors, and no other solutions worked. My error was: WindowsError: [Error 6] The handle is invalid.
I found that I had to assign PIPE to every handle to get it to return the output I expected - the following worked for me.
import subprocess
def run_command(cmd):
"""given shell command, returns communication tuple of stdout and stderr"""
return subprocess.Popen(cmd,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
stdin=subprocess.PIPE).communicate()
and call like this, ([0] gets the first element of the tuple, stdout):
run_command('tracert 11.1.0.1')[0]
After learning more, I believe I need these pipe arguments because I'm working on a custom system that uses different handles, so I had to directly control all the std's.
To stop console popups (with Windows), do this:
def run_command(cmd):
"""given shell command, returns communication tuple of stdout and stderr"""
# instantiate a startupinfo obj:
startupinfo = subprocess.STARTUPINFO()
# set the use show window flag, might make conditional on being in Windows:
startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
# pass as the startupinfo keyword argument:
return subprocess.Popen(cmd,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
stdin=subprocess.PIPE,
startupinfo=startupinfo).communicate()
run_command('tracert 11.1.0.1')
On Python 3.7+, use subprocess.run and pass capture_output=True:
import subprocess
result = subprocess.run(['echo', 'hello', 'world'], capture_output=True)
print(repr(result.stdout))
This will return bytes:
b'hello world\n'
If you want it to convert the bytes to a string, add text=True:
result = subprocess.run(['echo', 'hello', 'world'], capture_output=True, text=True)
print(repr(result.stdout))
This will read the bytes using your default encoding:
'hello world\n'
If you need to manually specify a different encoding, use encoding="your encoding" instead of text=True:
result = subprocess.run(['echo', 'hello', 'world'], capture_output=True, encoding="utf8")
print(repr(result.stdout))
Splitting the initial command for the subprocess might be tricky and cumbersome.
Use shlex.split() to help yourself out.
Sample command
git log -n 5 --since "5 years ago" --until "2 year ago"
The code
from subprocess import check_output
from shlex import split
res = check_output(split('git log -n 5 --since "5 years ago" --until "2 year ago"'))
print(res)
>>> b'commit 7696ab087a163e084d6870bb4e5e4d4198bdc61a\nAuthor: Artur Barseghyan...'
Without shlex.split() the code would look as follows
res = check_output([
'git',
'log',
'-n',
'5',
'--since',
'5 years ago',
'--until',
'2 year ago'
])
print(res)
>>> b'commit 7696ab087a163e084d6870bb4e5e4d4198bdc61a\nAuthor: Artur Barseghyan...'
Here a solution, working if you want to print output while process is running or not.
I added the current working directory also, it was useful to me more than once.
Hoping the solution will help someone :).
import subprocess
def run_command(cmd_and_args, print_constantly=False, cwd=None):
"""Runs a system command.
:param cmd_and_args: the command to run with or without a Pipe (|).
:param print_constantly: If True then the output is logged in continuous until the command ended.
:param cwd: the current working directory (the directory from which you will like to execute the command)
:return: - a tuple containing the return code, the stdout and the stderr of the command
"""
output = []
process = subprocess.Popen(cmd_and_args, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, cwd=cwd)
while True:
next_line = process.stdout.readline()
if next_line:
output.append(str(next_line))
if print_constantly:
print(next_line)
elif not process.poll():
break
error = process.communicate()[1]
return process.returncode, '\n'.join(output), error
For some reason, this one works on Python 2.7 and you only need to import os!
import os
def bash(command):
output = os.popen(command).read()
return output
print_me = bash('ls -l')
print(print_me)
If you need to run a shell command on multiple files, this did the trick for me.
import os
import subprocess
# Define a function for running commands and capturing stdout line by line
# (Modified from Vartec's solution because it wasn't printing all lines)
def runProcess(exe):
p = subprocess.Popen(exe, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
return iter(p.stdout.readline, b'')
# Get all filenames in working directory
for filename in os.listdir('./'):
# This command will be run on each file
cmd = 'nm ' + filename
# Run the command and capture the output line by line.
for line in runProcess(cmd.split()):
# Eliminate leading and trailing whitespace
line.strip()
# Split the output
output = line.split()
# Filter the output and print relevant lines
if len(output) > 2:
if ((output[2] == 'set_program_name')):
print filename
print line
Edit: Just saw Max Persson's solution with J.F. Sebastian's suggestion. Went ahead and incorporated that.
According to #senderle, if you use python3.6 like me:
def sh(cmd, input=""):
rst = subprocess.run(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, input=input.encode("utf-8"))
assert rst.returncode == 0, rst.stderr.decode("utf-8")
return rst.stdout.decode("utf-8")
sh("ls -a")
Will act exactly like you run the command in bash
Improvement for better logging.
For better output you can use iterator.
From below, we get better
from subprocess import Popen, getstatusoutput, PIPE
def shell_command(cmd):
result = Popen(cmd, shell=True, stdout=PIPE, stderr=PIPE)
output = iter(result.stdout.readline, b'')
error = iter(result.stderr.readline, b'')
print("##### OutPut ###")
for line in output:
print(line.decode("utf-8"))
print("###### Error ########")
for line in error:
print(error.decode("utf-8")) # Convert bytes to str
status, terminal_output = run_command(cmd)
print(terminal_output)
shell_command("ls") # this will display all the files & folders in directory
Other method using getstatusoutput ( Easy to understand)
from subprocess import Popen, getstatusoutput, PIPE
status_Code, output = getstausoutput(command)
print(output) # this will give the terminal output
# status_code, output = getstatusoutput("ls") # this will print the all files & folder available in the directory
If you use the subprocess python module, you are able to handle the STDOUT, STDERR and return code of command separately. You can see an example for the complete command caller implementation. Of course you can extend it with try..except if you want.
The below function returns the STDOUT, STDERR and Return code so you can handle them in the other script.
import subprocess
def command_caller(command=None)
sp = subprocess.Popen(command, stderr=subprocess.PIPE, stdout=subprocess.PIPE, shell=False)
out, err = sp.communicate()
if sp.returncode:
print(
"Return code: %(ret_code)s Error message: %(err_msg)s"
% {"ret_code": sp.returncode, "err_msg": err}
)
return sp.returncode, out, err
I would like to suggest simppl as an option for consideration. It is a module that is available via pypi: pip install simppl and was runs on python3.
simppl allows the user to run shell commands and read the output from the screen.
The developers suggest three types of use cases:
The simplest usage will look like this:
from simppl.simple_pipeline import SimplePipeline
sp = SimplePipeline(start=0, end=100):
sp.print_and_run('<YOUR_FIRST_OS_COMMAND>')
sp.print_and_run('<YOUR_SECOND_OS_COMMAND>') ```
To run multiple commands concurrently use:
commands = ['<YOUR_FIRST_OS_COMMAND>', '<YOUR_SECOND_OS_COMMAND>']
max_number_of_processes = 4
sp.run_parallel(commands, max_number_of_processes) ```
Finally, if your project uses the cli module, you can run directly another command_line_tool as part of a pipeline. The other tool will
be run from the same process, but it will appear from the logs as
another command in the pipeline. This enables smoother debugging and
refactoring of tools calling other tools.
from example_module import example_tool
sp.print_and_run_clt(example_tool.run, ['first_number', 'second_nmber'],
{'-key1': 'val1', '-key2': 'val2'},
{'--flag'}) ```
Note that the printing to STDOUT/STDERR is via python's logging module.
Here is a complete code to show how simppl works:
import logging
from logging.config import dictConfig
logging_config = dict(
version = 1,
formatters = {
'f': {'format':
'%(asctime)s %(name)-12s %(levelname)-8s %(message)s'}
},
handlers = {
'h': {'class': 'logging.StreamHandler',
'formatter': 'f',
'level': logging.DEBUG}
},
root = {
'handlers': ['h'],
'level': logging.DEBUG,
},
)
dictConfig(logging_config)
from simppl.simple_pipeline import SimplePipeline
sp = SimplePipeline(0, 100)
sp.print_and_run('ls')
Here is a simple and flexible solution that works on a variety of OS versions, and both Python 2 and 3, using IPython in shell mode:
from IPython.terminal.embed import InteractiveShellEmbed
my_shell = InteractiveShellEmbed()
result = my_shell.getoutput("echo hello world")
print(result)
Out: ['hello world']
It has a couple of advantages
It only requires an IPython install, so you don't really need to worry about your specific Python or OS version when using it, it comes with Jupyter - which has a wide range of support
It takes a simple string by default - so no need to use shell mode arg or string splitting, making it slightly cleaner IMO
It also makes it cleaner to easily substitute variables or even entire Python commands in the string itself
To demonstrate:
var = "hello world "
result = my_shell.getoutput("echo {var*2}")
print(result)
Out: ['hello world hello world']
Just wanted to give you an extra option, especially if you already have Jupyter installed
Naturally, if you are in an actual Jupyter notebook as opposed to a .py script you can also always do:
result = !echo hello world
print(result)
To accomplish the same.
The output can be redirected to a text file and then read it back.
import subprocess
import os
import tempfile
def execute_to_file(command):
"""
This function execute the command
and pass its output to a tempfile then read it back
It is usefull for process that deploy child process
"""
temp_file = tempfile.NamedTemporaryFile(delete=False)
temp_file.close()
path = temp_file.name
command = command + " > " + path
proc = subprocess.run(command, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, universal_newlines=True)
if proc.stderr:
# if command failed return
os.unlink(path)
return
with open(path, 'r') as f:
data = f.read()
os.unlink(path)
return data
if __name__ == "__main__":
path = "Somepath"
command = 'ecls.exe /files ' + path
print(execute(command))
eg, execute('ls -ahl')
differentiated three/four possible returns and OS platforms:
no output, but run successfully
output empty line, run successfully
run failed
output something, run successfully
function below
def execute(cmd, output=True, DEBUG_MODE=False):
"""Executes a bash command.
(cmd, output=True)
output: whether print shell output to screen, only affects screen display, does not affect returned values
return: ...regardless of output=True/False...
returns shell output as a list with each elment is a line of string (whitespace stripped both sides) from output
could be
[], ie, len()=0 --> no output;
[''] --> output empty line;
None --> error occured, see below
if error ocurs, returns None (ie, is None), print out the error message to screen
"""
if not DEBUG_MODE:
print "Command: " + cmd
# https://stackoverflow.com/a/40139101/2292993
def _execute_cmd(cmd):
if os.name == 'nt' or platform.system() == 'Windows':
# set stdin, out, err all to PIPE to get results (other than None) after run the Popen() instance
p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)
else:
# Use bash; the default is sh
p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True, executable="/bin/bash")
# the Popen() instance starts running once instantiated (??)
# additionally, communicate(), or poll() and wait process to terminate
# communicate() accepts optional input as stdin to the pipe (requires setting stdin=subprocess.PIPE above), return out, err as tuple
# if communicate(), the results are buffered in memory
# Read stdout from subprocess until the buffer is empty !
# if error occurs, the stdout is '', which means the below loop is essentially skipped
# A prefix of 'b' or 'B' is ignored in Python 2;
# it indicates that the literal should become a bytes literal in Python 3
# (e.g. when code is automatically converted with 2to3).
# return iter(p.stdout.readline, b'')
for line in iter(p.stdout.readline, b''):
# # Windows has \r\n, Unix has \n, Old mac has \r
# if line not in ['','\n','\r','\r\n']: # Don't print blank lines
yield line
while p.poll() is None:
sleep(.1) #Don't waste CPU-cycles
# Empty STDERR buffer
err = p.stderr.read()
if p.returncode != 0:
# responsible for logging STDERR
print("Error: " + str(err))
yield None
out = []
for line in _execute_cmd(cmd):
# error did not occur earlier
if line is not None:
# trailing comma to avoid a newline (by print itself) being printed
if output: print line,
out.append(line.strip())
else:
# error occured earlier
out = None
return out
else:
print "Simulation! The command is " + cmd
print ""

Sphinx-autodoc with napoleon (Google Doc String Style): Warnings and Errors about Block quotes and indention

I am using Sphinx 4.4.0 with napoleon extension (Google Doc String). I have this two problems
ARNING: Block quote ends without a blank line; unexpected unindent.
ERROR: Unexpected indentation.
I found something about it on the internet but can not fit this two my code. My problem is I even do not understand the messages. I do not see where the problem could be.
This is the code:
def read_and_validate_csv(basename, specs_and_rules):
"""Read a CSV file with respect to specifications about format and
rules about valid values.
Hints: Do not use objects of type type (e.g. str instead of "str") when
specificing the column type.
specs_and_rules = {
'TEMPLATES': {
'T1l': ('Int16', [-9, ' '])
},
'ColumnA': 'str',
'ColumnB': ('str', 'no answer'),
'ColumnC': None,
'ColumnD': (
'Int16',
-9, {
'len': [1, 2, (4-8)],
'val': [0, 1, (3-9)]
}
}
Returns:
(pandas.DataFrame): Result.
"""
This are the original messages:
.../bandas.py:docstring of buhtzology.bandas.read_and_validate_csv:11: WARNING: Block quote ends without a blank line; unexpected unindent.
.../bandas.py:docstring of buhtzology.bandas.read_and_validate_csv:15: ERROR: Unexpected indentation.
.../bandas.py:docstring of buhtzology.bandas.read_and_validate_csv:17: ERROR: Unexpected indentation.
.../bandas.py:docstring of buhtzology.bandas.read_and_validate_csv:19: WARNING: Block quote ends without a blank line; unexpected unindent.
.../bandas.py:docstring of buhtzology.bandas.read_and_validate_csv:20: WARNING: Block quote ends without a blank line; unexpected unindent.
reStructuredText is not Markdown, and indentation alone is not enough to demarcate the code block. reStructuredText calls this a literal block. Although the use of :: is one option, you might want to explicitly specify the language (overriding the default) with the use of the code-block directive.
Also I noticed that you have invalid syntax in your code block—a missing ) and extra spaces in your indentation—which could have caused those errors.
Try this.
def read_and_validate_csv(basename, specs_and_rules):
"""Read a CSV file with respect to specifications about format and
rules about valid values.
Hints: Do not use objects of type type (e.g. str instead of "str") when
specificing the column type.
.. code-block:: python
specs_and_rules = {
'TEMPLATES': {
'T1l': ('Int16', [-9, ' '])
},
'ColumnA': 'str',
'ColumnB': ('str', 'no answer'),
'ColumnC': None,
'ColumnD': (
'Int16',
-9, {
'len': [1, 2, (4-8)],
'val': [0, 1, (3-9)]
}
)
}
Returns:
(pandas.DataFrame): Result.
"""

wkhtmltopdf, 0.12.6, Warning: Blocked access to file

When upgrade wkhtmltopdf to 0.12.6, it came to such messages and the image did not show in the target pdf:
Warning: Blocked access to file /path/to/bpa_product_layering.png
BTW, the same source html file works well with 0.12.5
This is caused by the change of default behavior in version 0.12.6 of wkhtmltopdf. wkhtmltopdf disables local file access by default now. It could be solved by adding the command line parameter
--enable-local-file-access
or the combination
--disable-local-file-access --allow <path>
For those that are using laravel-snappy, add the 'enable-local-file-access' option in the config\snappy.php:
'pdf' => [
'enabled' => true,
'binary' => env('WKHTML_PDF_BINARY', '/usr/local/bin/wkhtmltopdf'),
'timeout' => false,
'options' => [
'enable-local-file-access' => true,
'orientation' => 'landscape',
'encoding' => 'UTF-8'
],
'env' => [],
],
'image' => [
'enabled' => true,
'binary' => env('WKHTML_IMG_BINARY', '/usr/local/bin/wkhtmltoimage'),
'timeout' => false,
'options' => [
'enable-local-file-access' => true,
'orientation' => 'landscape',
'encoding' => 'UTF-8'
],
'env' => [],
],
wkhtmltopdf disables local file access by default in the 0.12.6 version
Just bumping this thread with a correction in case you're still getting the same error in spite of using:
--enable-local-file-access
For some reason, this cmd line argument does not work when being specified after input/output files, you have to write this argument right after wkhtmltopdf.exe.
So
wkhtmltopdf.exe --enable-local-file-access input.html output.pdf
instead of other variants.
in my case, I put "enable-local-file-access": "", in options, it worked.
In Windows with Python, I came across a similar error as well when running code:
result = imgkit.from_file('postlayout.A.html', 'out.jpg', config=wkhtmltoimage_binaries)
Error:
Warning: Blocked access to file C:/XXXXXX/background.A.jpg
Error: Failed to load about:blank, with network status code 301 and
http status code 0 - Protocol "about" is unknown
What I did to resolve this:
Add variable options
kitoptions = {
"enable-local-file-access": None
}
Add options to call
FROM
result = imgkit.from_file('postlayout.A.html', 'out.jpg', config=wkhtmltoimage_binaries)
TO
result = imgkit.from_file('postlayout.A.html', 'out.jpg', config=wkhtmltoimage_binaries, options=kitoptions)
Full Source:
import imgkit
#library path to kit
path_wkthmltopdf = r'C:\Program Files\wkhtmltopdf\bin\wkhtmltoimage.exe'
wkhtmltoimage_binaries = imgkit.config(wkhtmltoimage=path_wkthmltopdf)
#OPTIONS
kitoptions = {
"enable-local-file-access": None
}
html_file_directory = r'C:\XXXX\template'
result = imgkit.from_file('postlayout.A.html', 'out.jpg', config=wkhtmltoimage_binaries, options=kitoptions)
if result:
print("successful")
else:
print("failed")
For the C API, contrary to what the documentation says, it's not load.blockLocalFileAccess but loadPage.blockLocalFileAccess that you must set to "false":
wkhtmltoimage_set_global_setting(settings, "loadPage.blockLocalFileAccess", "false");
Hopefully, the documentation will be updated soon; see issue #4763.
I confirm that the problem comes from the wkhtmltopdf version. For those on Symfony (3.4), just add an option in config.yml:
knp_snappy:
pdf:
options:
enable-local-file-access: true
I know am a bit late in party but just wanted to write clear example with c# here so one can understand clearly.
ProcessStartInfo proc = new ProcessStartInfo();
proc = new ProcessStartInfo();
proc.RedirectStandardError = true;
proc.UseShellExecute = false;
proc.WorkingDirectory = #"" + Config.WkhtmltopdfPath;
proc.FileName = #"" + Config.WkhtmltopdfPath + #"\wkhtmltopdf.exe";
proc.Arguments = #" --enable-local-file-access -T 0 -B 0 --page-width 210mm --page-height 450mm " + fileName + ".html " + fileName + ".pdf";
Process inkscape = Process.Start(proc);

Where is the ruby function 'powershell' defined?

I am using the msutter DSC module for puppet. While reading through the source code, I come across code like this (in dsc_configuration_provider.rb):
def create
Puppet.debug "\n" + ps_script_content('set')
output = powershell(ps_script_content('set'))
Puppet.debug output
end
What file defines the powershell function or method? Is it a ruby builtin? A puppet builtin? Inherited from a class? I know that it is being used to send text to powershell as a command and gathering results, but I need to see the source code to understand how to improve its error logging for my purposes, because certain powershell errors are being swallowed and no warnings are being printed to the Puppet log.
These lines in file dsc_provider_helpers.rb may be relevant:
provider.commands :powershell =>
if File.exists?("#{ENV['SYSTEMROOT']}\\sysnative\\WindowsPowershell\\v1.0\\powershell.exe")
"#{ENV['SYSTEMROOT']}\\sysnative\\WindowsPowershell\\v1.0\\powershell.exe"
elsif File.exists?("#{ENV['SYSTEMROOT']}\\system32\\WindowsPowershell\\v1.0\\powershell.exe")
"#{ENV['SYSTEMROOT']}\\system32\\WindowsPowershell\\v1.0\\powershell.exe"
else
'powershell.exe'
end
Surely this defines where the Powershell executable is located, but gives no indication how it is called and how its return value is derived. Are stdout and stderr combined? Am I given the text output or just the error code? etc.
This is core Puppet logic. When a provider has a command, like
commands :powershell => some binary
That is hooked up as a function powershell(*args).
You can see it with other providers like Chocolatey:
commands :chocolatey => chocolatey_command
def self.chocolatey_command
if Puppet::Util::Platform.windows?
# must determine how to get to params in ruby
#default_location = $chocolatey::params::install_location || ENV['ALLUSERSPROFILE'] + '\chocolatey'
chocopath = ENV['ChocolateyInstall'] ||
('C:\Chocolatey' if File.directory?('C:\Chocolatey')) ||
('C:\ProgramData\chocolatey' if File.directory?('C:\ProgramData\chocolatey')) ||
"#{ENV['ALLUSERSPROFILE']}\chocolatey"
chocopath += '\bin\choco.exe'
else
chocopath = 'choco.exe'
end
chocopath
end
Then other locations can just call chocolatey like a function with args:
chocolatey(*args)

Create a file descriptor in ruby

I am writing a script will perform various tasks with DSV or positional files. These tasks varies and are like creating an DB table for the file, or creating a shell script for parsing it.
As I have idealized my script would receive a "descriptor" as input to perform its tasks. It then would parse this descriptor and perform its tasks accordingly.
I came up with some ideas on how to specify the descriptor file, but didn't really manage to get something robust - probably due my inexperience in ruby.
It seems though, the best way to parse the descriptor would be using ruby language itself and then somehow catch parsing exceptions to turn into something more relevant to the context.
Example:
The file I will be reading looks like (myfile.dsv):
jhon,12343535,27/04/1984
dave,53245265,30/03/1977
...
Descriptor file myfile.des contains:
FILE_TYPE = "DSV"
DSV_SEPARATOR = ","
FIELDS = [
name => [:pos => 0, :type => "string"],
phone => [:pos => 1, :type => "number"],
birthdate => [:pos => 2, :type => "date", :mask = "dd/mm/yyyy"]
]
And the usage should be:
ruby script.rb myfile.des --task GenerateTable
So the program script.rb should load and parse the descriptor myfile.des and perform whatever tasks accordingly.
Any ideas on how to perform this?
Use YAML
Instead of rolling your own, use YAML from the standard library.
Sample YAML File
Name your file something like descriptor.yml, and fill it with:
---
:file_type: DSV
:dsv_separator: ","
:fields:
:name:
:pos: 0
:type: string
:phone:
:pos: 1
:type: number
:birthdate:
:pos: 2
:type: date
:mask: dd/mm/yyyy
Loading YAML
You can read your configuration back in with:
require 'yaml'
settings = YAML.load_file 'descriptor.yml'
This will return a settings Hash like:
{:file_type=>"DSV",
:dsv_separator=>",",
:fields=>
{:name=>{:pos=>0, :type=>"string"},
:phone=>{:pos=>1, :type=>"number"},
:birthdate=>{:pos=>2, :type=>"date", :mask=>"dd/mm/yyyy"}}}
which you can then access as needed to configure your application.

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