Operating System Utilities¶

PyObject* PyOS_FSPath(PyObject *path)¶: Return value: New reference.
Return the file system representation for path. If the object is a str or bytes object, then its reference count is incremented. If the object implements the os.PathLike interface, then __fspath__() is returned as long as it is a str or bytes object. Otherwise TypeError is raised and NULL is returned.

New in version 3.6.

int Py_FdIsInteractive(FILE *fp, const char *filename)¶: Return true (nonzero) if the standard I/O file fp with name filename is deemed interactive. This is the case for files for which isatty(fileno(fp)) is true. If the global flag Py_InteractiveFlag is true, this function also returns true if the filename pointer is NULL or if the name is equal to one of the strings '<stdin>' or '???'.

void PyOS_BeforeFork()¶: Function to prepare some internal state before a process fork. This should be called before calling fork() or any similar function that clones the current process. Only available on systems where fork() is defined.

Warning

The C fork() call should only be made from the “main” thread (of the “main” interpreter). The same is true for PyOS_BeforeFork().

New in version 3.7.

void PyOS_AfterFork_Parent()¶: Function to update some internal state after a process fork. This should be called from the parent process after calling fork() or any similar function that clones the current process, regardless of whether process cloning was successful. Only available on systems where fork() is defined.

Warning

The C fork() call should only be made from the “main” thread (of the “main” interpreter). The same is true for PyOS_AfterFork_Parent().

New in version 3.7.

void PyOS_AfterFork_Child()¶: Function to update internal interpreter state after a process fork. This must be called from the child process after calling fork(), or any similar function that clones the current process, if there is any chance the process will call back into the Python interpreter. Only available on systems where fork() is defined.

Warning

The C fork() call should only be made from the “main” thread (of the “main” interpreter). The same is true for PyOS_AfterFork_Child().

New in version 3.7.

See also

os.register_at_fork() allows registering custom Python functions to be called by PyOS_BeforeFork(), PyOS_AfterFork_Parent() and PyOS_AfterFork_Child().

void PyOS_AfterFork()¶: Function to update some internal state after a process fork; this should be called in the new process if the Python interpreter will continue to be used. If a new executable is loaded into the new process, this function does not need to be called.

Deprecated since version 3.7: This function is superseded by PyOS_AfterFork_Child().

int PyOS_CheckStack()¶: Return true when the interpreter runs out of stack space. This is a reliable check, but is only available when USE_STACKCHECK is defined (currently on Windows using the Microsoft Visual C++ compiler). USE_STACKCHECK will be defined automatically; you should never change the definition in your own code.

PyOS_sighandler_t PyOS_getsig(int i)¶: Return the current signal handler for signal i. This is a thin wrapper around either sigaction() or signal(). Do not call those functions directly! PyOS_sighandler_t is a typedef alias for void (*)(int).

PyOS_sighandler_t PyOS_setsig(int i, PyOS_sighandler_t h)¶: Set the signal handler for signal i to be h; return the old signal handler. This is a thin wrapper around either sigaction() or signal(). Do not call those functions directly! PyOS_sighandler_t is a typedef alias for void (*)(int).

wchar_t* Py_DecodeLocale(const char* arg, size_t *size)¶

Decode a byte string from the locale encoding with the surrogateescape error handler: undecodable bytes are decoded as characters in range U+DC80..U+DCFF. If a byte sequence can be decoded as a surrogate character, escape the bytes using the surrogateescape error handler instead of decoding them.

Encoding, highest priority to lowest priority:

UTF-8 on macOS, Android, and VxWorks;
UTF-8 on Windows if Py_LegacyWindowsFSEncodingFlag is zero;
UTF-8 if the Python UTF-8 mode is enabled;
ASCII if the LC_CTYPE locale is "C", nl_langinfo(CODESET) returns the ASCII encoding (or an alias), and mbstowcs() and wcstombs() functions uses the ISO-8859-1 encoding.
the current locale encoding.

Return a pointer to a newly allocated wide character string, use PyMem_RawFree() to free the memory. If size is not NULL, write the number of wide characters excluding the null character into *size

Return NULL on decoding error or memory allocation error. If size is not NULL, *size is set to (size_t)-1 on memory error or set to (size_t)-2 on decoding error.

Decoding errors should never happen, unless there is a bug in the C library.

Use the Py_EncodeLocale() function to encode the character string back to a byte string.

System Functions¶

These are utility functions that make functionality from the sys module accessible to C code. They all work with the current interpreter thread’s sys module’s dict, which is contained in the internal thread state structure.

PyObject *PySys_GetObject(const char *name)¶: Return value: Borrowed reference.
Return the object name from the sys module or NULL if it does not exist, without setting an exception.

int PySys_SetObject(const char *name, PyObject *v)¶: Set name in the sys module to v unless v is NULL, in which case name is deleted from the sys module. Returns 0 on success, -1 on error.

void PySys_ResetWarnOptions()¶: Reset sys.warnoptions to an empty list. This function may be called prior to Py_Initialize().

void PySys_AddWarnOption(const wchar_t *s)¶: Append s to sys.warnoptions. This function must be called prior to Py_Initialize() in order to affect the warnings filter list.

void PySys_AddWarnOptionUnicode(PyObject *unicode)¶

Append unicode to sys.warnoptions.

Note: this function is not currently usable from outside the CPython implementation, as it must be called prior to the implicit import of warnings in Py_Initialize() to be effective, but can’t be called until enough of the runtime has been initialized to permit the creation of Unicode objects.

void PySys_SetPath(const wchar_t *path)¶: Set sys.path to a list object of paths found in path which should be a list of paths separated with the platform’s search path delimiter (: on Unix, ; on Windows).

void PySys_WriteStdout(const char *format, ...)¶

Write the output string described by format to sys.stdout. No exceptions are raised, even if truncation occurs (see below).

format should limit the total size of the formatted output string to 1000 bytes or less – after 1000 bytes, the output string is truncated. In particular, this means that no unrestricted “%s” formats should occur; these should be limited using “%.<N>s” where <N> is a decimal number calculated so that <N> plus the maximum size of other formatted text does not exceed 1000 bytes. Also watch out for “%f”, which can print hundreds of digits for very large numbers.

If a problem occurs, or sys.stdout is unset, the formatted message is written to the real (C level) stdout.

void PySys_WriteStderr(const char *format, ...)¶: As PySys_WriteStdout(), but write to sys.stderr or stderr instead.

void PySys_FormatStdout(const char *format, ...)¶: Function similar to PySys_WriteStdout() but format the message using PyUnicode_FromFormatV() and don’t truncate the message to an arbitrary length.

New in version 3.2.

void PySys_FormatStderr(const char *format, ...)¶: As PySys_FormatStdout(), but write to sys.stderr or stderr instead.

New in version 3.2.

void PySys_AddXOption(const wchar_t *s)¶: Parse s as a set of -X options and add them to the current options mapping as returned by PySys_GetXOptions(). This function may be called prior to Py_Initialize().

New in version 3.2.

PyObject *PySys_GetXOptions()¶: Return value: Borrowed reference.
Return the current dictionary of -X options, similarly to sys._xoptions. On error, NULL is returned and an exception is set.

New in version 3.2.

int PySys_Audit(const char *event, const char *format, ...)¶

Raise an auditing event with any active hooks. Return zero for success and non-zero with an exception set on failure.

If any hooks have been added, format and other arguments will be used to construct a tuple to pass. Apart from N, the same format characters as used in Py_BuildValue() are available. If the built value is not a tuple, it will be added into a single-element tuple. (The N format option consumes a reference, but since there is no way to know whether arguments to this function will be consumed, using it may cause reference leaks.)

Note that # format characters should always be treated as Py_ssize_t, regardless of whether PY_SSIZE_T_CLEAN was defined.

sys.audit() performs the same function from Python code.

New in version 3.8.

Changed in version 3.8.2: Require Py_ssize_t for # format characters. Previously, an unavoidable deprecation warning was raised.

int PySys_AddAuditHook(Py_AuditHookFunction hook, void *userData)¶

Append the callable hook to the list of active auditing hooks. Return zero for success and non-zero on failure. If the runtime has been initialized, also set an error on failure. Hooks added through this API are called for all interpreters created by the runtime.

The userData pointer is passed into the hook function. Since hook functions may be called from different runtimes, this pointer should not refer directly to Python state.

This function is safe to call before Py_Initialize(). When called after runtime initialization, existing audit hooks are notified and may silently abort the operation by raising an error subclassed from Exception (other errors will not be silenced).

The hook function is of type int (*)(const char *event, PyObject *args, void *userData), where args is guaranteed to be a PyTupleObject. The hook function is always called with the GIL held by the Python interpreter that raised the event.

See PEP 578 for a detailed description of auditing. Functions in the runtime and standard library that raise events are listed in the audit events table. Details are in each function’s documentation.

If the interpreter is initialized, this function raises a auditing event sys.addaudithook with no arguments. If any existing hooks raise an exception derived from Exception, the new hook will not be added and the exception is cleared. As a result, callers cannot assume that their hook has been added unless they control all existing hooks.

New in version 3.8.

Process Control¶

void Py_FatalError(const char *message)¶

Print a fatal error message and kill the process. No cleanup is performed. This function should only be invoked when a condition is detected that would make it dangerous to continue using the Python interpreter; e.g., when the object administration appears to be corrupted. On Unix, the standard C library function abort() is called which will attempt to produce a core file.

The Py_FatalError() function is replaced with a macro which logs automatically the name of the current function, unless the Py_LIMITED_API macro is defined.

Changed in version 3.9: Log the function name automatically.

void Py_Exit(int status)¶: Exit the current process. This calls Py_FinalizeEx() and then calls the standard C library function exit(status). If Py_FinalizeEx() indicates an error, the exit status is set to 120.

Changed in version 3.6: Errors from finalization no longer ignored.

int Py_AtExit(void (*func)())¶: Register a cleanup function to be called by Py_FinalizeEx(). The cleanup function will be called with no arguments and should return no value. At most 32 cleanup functions can be registered. When the registration is successful, Py_AtExit() returns 0; on failure, it returns -1. The cleanup function registered last is called first. Each cleanup function will be called at most once. Since Python’s internal finalization will have completed before the cleanup function, no Python APIs should be called by func.

Operating System Utilities¶

System Functions¶

Process Control¶

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