如何在 Python3 中使用子进程指定 LD_LIBRARY_PATH？

Question

I am trying to specify LD_LIBRARY_PATH before the executable name while using subprocess in python3 but getting an error specified next.

Can you explain what is wrong? I just want to pass LD_LIBRARY_PATH before the exe name having multiple key-value pair arguments as shown.

   myFile = "/home/user1/file1.txt"
   output_path="/usr/local/dir1/dir2/bin/myExe"
   
   if os.name != 'nt':
        libpath = "LD_LIBRARY_PATH=" + os.path.dirname(output_path)
        output_path = libpath + " " + output_path;

    print("\n Output path is '{}'".format(output_path))
    
    opt1 = ['--input', myFile]
    child = subprocess.Popen([output_path, "--header", *opt1,
                                                      '--opt2', 'one' '--opt2', 'two'],
                                                     shell=False, stderr=subprocess.STDOUT, stdout=subprocess.PIPE)
    # output bytes
    output = child.communicate()[0]
    # exit code
    rc = child.returncode

Error given is as below

FileNotFoundError: [Errno 2] No such file or directory: 'LD_LIBRARY_PATH=/usr/local/dir1/dir2/bin /usr/local/dir1/dir2/bin/myExe': 'LD_LIBRARY_PATH=/usr/local/dir1/dir2/bin /usr/local/dir1/dir2/bin/myExe'

Answer 1

You are attempting to use the POSIX shell syntax for specifying environment variables when invoking a command, but you are explicitly telling Python not to invoke a shell (which is good, since using shell=True leads to non-portable code, and is unnecessary here). Incidentally, shell=False is the default so you don't need to specify it.

To specify environment variables for Popen , pass them as a mapping to the env parameter. Be sure to include all environment variables though, not just the ones you want to change:

output_path = '/usr/local/dir1/dir2/bin/myExe'

env = os.environ.copy()
env.update(LD_LIBRARY_PATH = os.path.dirname(output_path))

child = subprocess.Popen(
    [output_path, '--header', *opt1, '--opt2', 'one' '--opt2', 'two'],
    stdout=subprocess.PIPE,
    stderr=subprocess.STDOUT,
    env=env
)