If the directory already exists, FileExistsError is raised. On some systems, mode is ignored. Where it is used, the current umask value is first masked out. If bits other than the last 9 i.
On some platforms, they are ignored and you should call chmod explicitly to set them. Recursive directory creation function. Like mkdir , but makes all intermediate-level directories needed to contain the leaf directory.
The mode parameter is passed to mkdir for creating the leaf directory; see the mkdir description for how it is interpreted. To set the file permission bits of any newly-created parent directories you can set the umask before invoking makedirs. The file permission bits of existing parent directories are not changed. Since this behavior was impossible to implement safely, it was removed in Python 3. See bpo Create a FIFO a named pipe named path with numeric mode mode.
The current umask value is first masked out from the mode. FIFOs are pipes that can be accessed like regular files. FIFOs exist until they are deleted for example with os. Create a filesystem node file, device special file or named pipe named path. For stat. Return system configuration information relevant to a named file.
Dictionary mapping names accepted by pathconf and fpathconf to the integer values defined for those names by the host operating system. This can be used to determine the set of names known to the system. Return a string representing the path to which the symbolic link points. The result may be either an absolute or relative pathname; if it is relative, it may be converted to an absolute pathname using os. If the path is a string object directly or indirectly through a PathLike interface , the result will also be a string object, and the call may raise a UnicodeDecodeError.
If the path is a bytes object direct or indirectly , the result will be a bytes object. Remove delete the file path.
If path is a directory, OSError is raised. Use rmdir to remove directories. This function can support paths relative to directory descriptors. On Windows, attempting to remove a file that is in use causes an exception to be raised; on Unix, the directory entry is removed but the storage allocated to the file is not made available until the original file is no longer in use.
This function is semantically identical to unlink. Remove directories recursively. Works like rmdir except that, if the leaf directory is successfully removed, removedirs tries to successively remove every parent directory mentioned in path until an error is raised which is ignored, because it generally means that a parent directory is not empty. For example, os. Raises OSError if the leaf directory could not be successfully removed.
Rename the file or directory src to dst. If dst is a directory, OSError will be raised. On Unix, if dst exists and is a file, it will be replaced silently if the user has permission. The operation may fail on some Unix flavors if src and dst are on different filesystems. On Windows, if dst already exists, OSError will be raised even if it is a file. If you want cross-platform overwriting of the destination, use replace. Recursive directory or file renaming function. Works like rename , except creation of any intermediate directories needed to make the new pathname good is attempted first.
After the rename, directories corresponding to rightmost path segments of the old name will be pruned away using removedirs. This function can fail with the new directory structure made if you lack permissions needed to remove the leaf directory or file. If dst exists and is a file, it will be replaced silently if the user has permission. The operation may fail if src and dst are on different filesystems. Remove delete the directory path.
Only works when the directory is empty, otherwise, OSError is raised. In order to remove whole directory trees, shutil.
Return an iterator of os. DirEntry objects corresponding to the entries in the directory given by path. The entries are yielded in arbitrary order, and the special entries '. Using scandir instead of listdir can significantly increase the performance of code that also needs file type or file attribute information, because os.
DirEntry objects expose this information if the operating system provides it when scanning a directory. All os. If path is of type bytes directly or indirectly through the PathLike interface , the type of the name and path attributes of each os.
DirEntry will be bytes ; in all other circumstances, they will be of type str. The scandir iterator supports the context manager protocol and has the following method:. This is called automatically when the iterator is exhausted or garbage collected, or when an error happens during iterating. However it is advisable to call it explicitly or use the with statement. The entry. If a scandir iterator is neither exhausted nor explicitly closed a ResourceWarning will be emitted in its destructor.
The function accepts a path-like object. Object yielded by scandir to expose the file path and other file attributes of a directory entry. When a stat or lstat system call is made, the os. DirEntry object will cache the result. DirEntry instances are not intended to be stored in long-lived data structures; if you know the file metadata has changed or if a long time has elapsed since calling scandir , call os.
Because the os. DirEntry methods can make operating system calls, they may also raise OSError. If you need very fine-grained control over errors, you can catch OSError when calling one of the os.
DirEntry methods and handle as appropriate. To be directly usable as a path-like object , os. DirEntry implements the PathLike interface. Attributes and methods on a os. DirEntry instance are as follows:. The name attribute will be bytes if the scandir path argument is of type bytes and str otherwise. Use fsdecode to decode byte filenames. The path is only absolute if the scandir path argument was absolute.
If the scandir path argument was a file descriptor , the path attribute is the same as the name attribute. The path attribute will be bytes if the scandir path argument is of type bytes and str otherwise.
The result is cached on the os. DirEntry object. Call os. On the first, uncached call, no system call is required in most cases. Specifically, for non-symlinks, neither Windows or Unix require a system call, except on certain Unix file systems, such as network file systems, that return dirent. Specifically, neither Windows or Unix require a system call, except on certain Unix file systems, such as network file systems, that return dirent.
On Unix, this method always requires a system call. Note that there is a nice correspondence between several attributes and methods of os. DirEntry and of pathlib. Added support for bytes paths on Windows. Get the status of a file or a file descriptor. Perform the equivalent of a stat system call on the given path. This function can support specifying a file descriptor and not following symlinks. Object whose attributes correspond roughly to the members of the stat structure.
It is used for the result of os. Size of the file in bytes, if it is a regular file or a symbolic link. The size of a symbolic link is the length of the pathname it contains, without a terminating null byte. See your operating system documentation for details. Number of byte blocks allocated for file. Writing to a file in smaller chunks may cause an inefficient read-modify-rewrite.
On other Unix systems such as FreeBSD , the following attributes may be available but may be only filled out if root tries to use them :. The standard module stat defines functions and constants that are useful for extracting information from a stat structure.
On Windows, some items are filled with dummy values. More items may be added at the end by some implementations. Perform a statvfs system call on the given path. Different platforms provide different functionality, and an option that might work on one might be unsupported on another. If the local platform supports it, the collection will contain os. A Set object indicating which functions in the os module permit specifying their path parameter as an open file descriptor. As an example, this expression determines whether os.
On Windows, a symlink represents either a file or a directory, and does not morph to the target dynamically. If the target is present, the type of the symlink will be created to match. Symbolic link support was introduced in Windows 6. This privilege is not typically granted to regular users but is available to accounts which can escalate privileges to the administrator level. Either obtaining the privilege or running your application as an administrator are ways to successfully create symlinks.
OSError is raised when the function is called by an unprivileged user. Truncate the file corresponding to path , so that it is at most length bytes in size.
This function is semantically identical to remove ; the unlink name is its traditional Unix name. Please see the documentation for remove for further information. These specify the times set on path and are used as follows:. Whether a directory can be given for path depends on whether the operating system implements directories as files for example, Windows does not. Note that the exact times you set here may not be returned by a subsequent stat call, depending on the resolution with which your operating system records access and modification times; see stat.
Generate the file names in a directory tree by walking the tree either top-down or bottom-up. For each directory in the tree rooted at directory top including top itself , it yields a 3-tuple dirpath, dirnames, filenames. Note that the names in the lists contain no path components.
To get a full path which begins with top to a file or directory in dirpath , do os. If optional argument topdown is True or not specified, the triple for a directory is generated before the triples for any of its subdirectories directories are generated top-down. If topdown is False , the triple for a directory is generated after the triples for all of its subdirectories directories are generated bottom-up.
No matter the value of topdown , the list of subdirectories is retrieved before the tuples for the directory and its subdirectories are generated. When topdown is True , the caller can modify the dirnames list in-place perhaps using del or slice assignment , and walk will only recurse into the subdirectories whose names remain in dirnames ; this can be used to prune the search, impose a specific order of visiting, or even to inform walk about directories the caller creates or renames before it resumes walk again.
Modifying dirnames when topdown is False has no effect on the behavior of the walk, because in bottom-up mode the directories in dirnames are generated before dirpath itself is generated. By default, errors from the listdir call are ignored. If optional argument onerror is specified, it should be a function; it will be called with one argument, an OSError instance. It can report the error to continue with the walk, or raise the exception to abort the walk.
Note that the filename is available as the filename attribute of the exception object. By default, walk will not walk down into symbolic links that resolve to directories. Set followlinks to True to visit directories pointed to by symlinks, on systems that support them. Whether or not the lists are sorted depends on the file system. If a file is removed from or added to the dirpath directory during generating the lists, whether a name for that file be included is unspecified. If optional argument topdown is True or not specified, the triple for a directory is generated before the triples for any of its subdirectories directories are generated top-down.
If topdown is False , the triple for a directory is generated after the triples for all of its subdirectories directories are generated bottom-up. No matter the value of topdown , the list of subdirectories is retrieved before the tuples for the directory and its subdirectories are generated. When topdown is True , the caller can modify the dirnames list in-place perhaps using del or slice assignment , and walk will only recurse into the subdirectories whose names remain in dirnames ; this can be used to prune the search, impose a specific order of visiting, or even to inform walk about directories the caller creates or renames before it resumes walk again.
Modifying dirnames when topdown is False has no effect on the behavior of the walk, because in bottom-up mode the directories in dirnames are generated before dirpath itself is generated. By default, errors from the scandir call are ignored. If optional argument onerror is specified, it should be a function; it will be called with one argument, an OSError instance. It can report the error to continue with the walk, or raise the exception to abort the walk.
Note that the filename is available as the filename attribute of the exception object. By default, walk will not walk down into symbolic links that resolve to directories. Set followlinks to True to visit directories pointed to by symlinks, on systems that support them.
Be aware that setting followlinks to True can lead to infinite recursion if a link points to a parent directory of itself. In the next example simple implementation of shutil. This function always supports paths relative to directory descriptors and not following symlinks. Since fwalk yields file descriptors, those are only valid until the next iteration step, so you should duplicate them e.
Create an anonymous file and return a file descriptor that refers to it. By default, the new file descriptor is non-inheritable.
The displayed name is always prefixed with memfd: and serves only for debugging purposes. Names do not affect the behavior of the file descriptor, and as such multiple files can have the same name without any side effects. Availability : Linux 3. Create and return an event file descriptor.
The file descriptors supports raw read and write with a buffer size of 8, select , poll and similar. See man page eventfd 2 for more information. The initial value must be an 32 bit unsigned integer. Please note that the initial value is limited to a 32 bit unsigned int although the event counter is an unsigned 64 bit integer with a maximum value of 2 64 Write blocks if the write operation would increment the counter to a value larger than 2 64 Read value from an eventfd file descriptor and return a 64 bit unsigned int.
The function does not verify that fd is an eventfd. Availability : See eventfd. Add value to an eventfd file descriptor. Set close-on-exec flag for new eventfd file descriptor. Provide semaphore-like semantics for reads from a eventfd file descriptor. On read the internal counter is decremented by one.
Return the value of the extended filesystem attribute attribute for path. If it is str, it is encoded with the filesystem encoding. Return a list of the extended filesystem attributes on path. The attributes in the list are represented as strings decoded with the filesystem encoding. If path is None , listxattr will examine the current directory.
Removes the extended filesystem attribute attribute from path. If it is a string, it is encoded with the filesystem encoding and error handler. Set the extended filesystem attribute attribute on path to value. If it is a str, it is encoded with the filesystem encoding and error handler. A bug in Linux kernel versions less than 2. This is a possible value for the flags argument in setxattr.
It indicates the operation must create an attribute. It indicates the operation must replace an existing attribute. In each case, the first of these arguments is passed to the new program as its own name rather than as an argument a user may have typed on a command line. On Unix, the default behavior is to produce a core dump; on Windows, the process immediately returns an exit code of 3.
This search path is used when resolving dependencies for imported extension modules the module itself is resolved through sys. Remove the directory by calling close on the returned object or using it in a with statement. See the Microsoft documentation for more information about how DLLs are loaded. See the porting notes for information on updating libraries. These functions all execute a new program, replacing the current process; they do not return.
On Unix, the new executable is loaded into the current process, and will have the same process id as the caller. Errors will be reported as OSError exceptions.
The current process is replaced immediately. Open file objects and descriptors are not flushed, so if there may be data buffered on these open files, you should flush them using sys. In either case, the arguments to the child process should start with the name of the command being run, but this is not enforced.
The other variants, execl , execle , execv , and execve , will not use the PATH variable to locate the executable; path must contain an appropriate absolute or relative path. For execve on some platforms, path may also be specified as an open file descriptor.
This functionality may not be supported on your platform; you can check whether or not it is available using os. Exit the process with status n , without calling cleanup handlers, flushing stdio buffers, etc. The standard way to exit is sys. Some of these may not be available on all Unix platforms, since there is some variation. These constants are defined where they are defined by the underlying platform.
Exit code that means the command was used incorrectly, such as when the wrong number of arguments are given. Exit code that means an operating system error was detected, such as the inability to fork or create a pipe.
Exit code that means some system file did not exist, could not be opened, or had some other kind of error. Exit code that means a temporary failure occurred. Exit code that means that there were insufficient permissions to perform the operation but not intended for file system problems.
Fork a child process. If an error occurs OSError is raised. See ssl for applications that use the SSL module with fork. For a more portable approach, use the pty module. Send signal sig to the process pid. Constants for the specific signals available on the host platform are defined in the signal module. Windows: The signal. Any other value for sig will cause the process to be unconditionally killed by the TerminateProcess API, and the exit code will be set to sig.
The Windows version of kill additionally takes process handles to be killed. See also signal. Return a file descriptor referring to the process pid. This descriptor can be used to perform process management without races and signals. The flags argument is provided for future extensions; no flag values are currently defined. Availability : Linux 5. Lock program segments into memory. Open a pipe to or from command cmd.
The return value is an open file object connected to the pipe, which can be read or written depending on whether mode is 'r' default or 'w'.
The buffering argument has the same meaning as the corresponding argument to the built-in open function. The returned file object reads or writes text strings rather than bytes.
On POSIX systems, if the return code is positive it represents the return value of the process left-shifted by one byte. If the return code is negative, the process was terminated by the signal given by the negated value of the return code. For example, the return value might be - signal. On Windows systems, the return value contains the signed integer return code from the child process.
On Windows, the close method result is directly the exit code or None. This is implemented using subprocess. Most users should use subprocess. The positional-only arguments path , args , and env are similar to execve. The path parameter is the path to the executable file. The path should contain a directory. The first item in each tuple must be one of the three type indicator listed below describing the remaining tuple elements:. Performs os. The setpgroup argument will set the process group of the child to the value specified.
Otherwise, NotImplementedError is raised. The setsigmask argument will set the signal mask to the signal set specified. The sigdef argument will reset the disposition of all signals in the set specified. A value of None in the place of the scheduler policy indicates that is not being provided. Register callables to be executed when a new child process is forked using os. The parameters are optional and keyword-only. Each specifies a different call point.
These calls are only made if control is expected to return to the Python interpreter. A typical subprocess launch will not trigger them as the child is not going to re-enter the interpreter.
Functions registered for execution before forking are called in reverse registration order. Functions registered for execution after forking either in the parent or in the child are called in registration order.
Note that the subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using these functions. Check especially the Replacing Older Functions with the subprocess Module section. On Windows, the process id will actually be the process handle, so can be used with the waitpid function.
Instead it raises OSError exception. In either case, the arguments to the child process must start with the name of the command being run. The other variants, spawnl , spawnle , spawnv , and spawnve , will not use the PATH variable to locate the executable; path must contain an appropriate absolute or relative path.
Note that keys and values in the env dictionary must be strings; invalid keys or values will cause the function to fail, with a return value of As an example, the following calls to spawnlp and spawnvpe are equivalent:. These are less portable than those listed above. When operation is not specified or 'open' , this acts like double-clicking the file in Windows Explorer, or giving the file name as an argument to the start command from the interactive command shell: the file is opened with whatever application if any its extension is associated.
Common verbs documented by Microsoft are 'print' and 'edit' to be used on files as well as 'explore' and 'find' to be used on directories. When launching an application, specify arguments to be passed as a single string. This argument may have no effect when using this function to launch a document. The default working directory is inherited, but may be overridden by the cwd argument.
This should be an absolute path. A relative path will be resolved against this argument. Whether this has any effect will depend on the application being launched. Values are integers as supported by the Win32 ShellExecute function. The path parameter is relative to the current directory or cwd. To reduce interpreter startup overhead, the Win32 ShellExecute function is not resolved until this function is first called. If the function cannot be resolved, NotImplementedError will be raised. Execute the command a string in a subshell.
This is implemented by calling the Standard C function system , and has the same limitations. Changes to sys. If command generates any output, it will be sent to the interpreter standard output stream.
The C standard does not specify the meaning of the return value of the C function, so the return value of the Python function is system-dependent. On Unix, the return value is the exit status of the process encoded in the format specified for wait. On Windows, the return value is that returned by the system shell after running command. The subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using this function.
See the Replacing Older Functions with the subprocess Module section in the subprocess documentation for some helpful recipes. On Windows, the result is directly the exit code. On Windows, only user and system are known; the other attributes are zero. Wait for completion of a child process, and return a tuple containing its pid and exit status indication: a bit number, whose low byte is the signal number that killed the process, and whose high byte is the exit status if the signal number is zero ; the high bit of the low byte is set if a core file was produced.
Wait for the completion of one or more child processes. These are the possible values for idtype in waitid. They affect how id is interpreted. This is a Linux-specific idtype that indicates that id is a file descriptor that refers to a process. Flags that can be used in options in waitid that specify what child signal to wait for.
On Unix: Wait for completion of a child process given by process id pid , and return a tuple containing its process id and exit status indication encoded as for wait. The semantics of the call are affected by the value of the integer options , which should be 0 for normal operation. If pid is greater than 0 , waitpid requests status information for that specific process. If pid is 0 , the request is for the status of any child in the process group of the current process.
If pid is -1 , the request pertains to any child of the current process. If pid is less than -1 , status is requested for any process in the process group -pid the absolute value of pid. How are we doing? Please help us improve Stack Overflow. Take our short survey. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. How to determine pid of process started via os. Asked 8 years, 1 month ago. Active 4 years, 2 months ago. Viewed 28k times. Sebastian Werk. Sebastian Werk Sebastian Werk 1, 2 2 gold badges 14 14 silver badges 28 28 bronze badges. The question that you've linked shows different case and anyway the time difference is a couple of milliseconds.
Yes, I have measured it. It was around 20 to 30ms, which was in my specific case too slow, since I had a scrolling graphic, which had to be updated multiple times per second. You can set the exit status to a nonzero value if the spawned process specifically calls the exit routine with a nonzero argument. If the new process did not explicitly set a positive exit status, a positive exit status indicates an abnormal exit with an abort or an interrupt.
A return value of -1 indicates an error the new process is not started. In this case, errno is set to one of the following values. These functions validate their parameters. If either cmdname or arg0 is an empty string or a null pointer, the invalid parameter handler is invoked, as described in Parameter Validation.
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