.. highlightlang:: c

.. _os:

Operating System Utilities

.. c:function:: PyObject* PyOS_FSPath(PyObject *path)

Return the file system representation for path. If the object is a :class:str or :class:bytes object, then its reference count is incremented. If the object implements the :class:os.PathLike interface, then :meth:~os.PathLike.__fspath__ is returned as long as it is a :class:str or :class:bytes object. Otherwise :exc:TypeError is raised and NULL is returned.

.. versionadded:: 3.6

.. c:function:: 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 :c:data: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 '???'.

.. c:function:: void PyOS_BeforeFork()

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

.. versionadded:: 3.7

.. c:function:: void PyOS_AfterFork_Parent()

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

.. versionadded:: 3.7

.. c:function:: void PyOS_AfterFork_Child()

Function to update internal interpreter state after a process fork. This must be called from the child process after calling :c:func: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 :c:func:fork is defined.

.. versionadded:: 3.7

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

.. c:function:: 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 deprecated:: 3.7 This function is superseded by :c:func:PyOS_AfterFork_Child().

.. c:function:: int PyOS_CheckStack()

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

.. c:function:: PyOS_sighandler_t PyOS_getsig(int i)

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

.. c:function:: 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 :c:func:sigaction or :c:func:signal. Do not call those functions directly! :c:type:PyOS_sighandler_t is a typedef alias for :c:type:void (\*)(int).

.. c:function:: wchar_t* Py_DecodeLocale(const char* arg, size_t *size)

Decode a byte string from the locale encoding with the :ref:surrogateescape error handler <surrogateescape>: 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 and Android;
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 :c:func:mbstowcs and :c:func:wcstombs functions uses the ISO-8859-1 encoding.
the current locale encoding.

Return a pointer to a newly allocated wide character string, use :c:func: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 :c:func:Py_EncodeLocale function to encode the character string back to a byte string.

.. seealso::

  The :c:func:`PyUnicode_DecodeFSDefaultAndSize` and
  :c:func:`PyUnicode_DecodeLocaleAndSize` functions.

.. versionadded:: 3.5

.. versionchanged:: 3.7 The function now uses the UTF-8 encoding in the UTF-8 mode.

.. c:function:: char* Py_EncodeLocale(const wchar_t *text, size_t *error_pos)

Encode a wide character string to the locale encoding with the :ref:surrogateescape error handler <surrogateescape>: surrogate characters in the range U+DC80..U+DCFF are converted to bytes 0x80..0xFF.

Encoding, highest priority to lowest priority:

UTF-8 on macOS and Android;
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 :c:func:mbstowcs and :c:func:wcstombs functions uses the ISO-8859-1 encoding.
the current locale encoding.

The function uses the UTF-8 encoding in the Python UTF-8 mode.

Return a pointer to a newly allocated byte string, use :c:func:PyMem_Free to free the memory. Return NULL on encoding error or memory allocation error

If error_pos is not NULL, *error_pos is set to (size_t)-1 on success, or set to the index of the invalid character on encoding error.

Use the :c:func:Py_DecodeLocale function to decode the bytes string back to a wide character string.

.. versionchanged:: 3.7 The function now uses the UTF-8 encoding in the UTF-8 mode.

.. seealso::

  The :c:func:`PyUnicode_EncodeFSDefault` and
  :c:func:`PyUnicode_EncodeLocale` functions.

.. versionadded:: 3.5

.. versionchanged:: 3.7 The function now supports the UTF-8 mode.

.. _systemfunctions:

System Functions

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

.. c:function:: PyObject *PySys_GetObject(const char *name)

Return the object name from the :mod:sys module or NULL if it does not exist, without setting an exception.

.. c:function:: int PySys_SetObject(const char *name, PyObject *v)

Set name in the :mod: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.

.. c:function:: void PySys_ResetWarnOptions()

Reset :data:sys.warnoptions to an empty list. This function may be called prior to :c:func:Py_Initialize.

.. c:function:: void PySys_AddWarnOption(const wchar_t *s)

Append s to :data:sys.warnoptions. This function must be called prior to :c:func:Py_Initialize in order to affect the warnings filter list.

.. c:function:: void PySys_AddWarnOptionUnicode(PyObject *unicode)

Append unicode to :data: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 :mod:warnings in :c:func: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.

.. c:function:: void PySys_SetPath(const wchar_t *path)

Set :data: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).

.. c:function:: void PySys_WriteStdout(const char *format, ...)

Write the output string described by format to :data: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 :data:sys.stdout is unset, the formatted message is written to the real (C level) stdout.

.. c:function:: void PySys_WriteStderr(const char *format, ...)

As :c:func:PySys_WriteStdout, but write to :data:sys.stderr or stderr instead.

.. c:function:: void PySys_FormatStdout(const char *format, ...)

Function similar to PySys_WriteStdout() but format the message using :c:func:PyUnicode_FromFormatV and don't truncate the message to an arbitrary length.

.. versionadded:: 3.2

.. c:function:: void PySys_FormatStderr(const char *format, ...)

As :c:func:PySys_FormatStdout, but write to :data:sys.stderr or stderr instead.

.. versionadded:: 3.2

.. c:function:: void PySys_AddXOption(const wchar_t *s)

Parse s as a set of :option:-X options and add them to the current options mapping as returned by :c:func:PySys_GetXOptions. This function may be called prior to :c:func:Py_Initialize.

.. versionadded:: 3.2

.. c:function:: PyObject *PySys_GetXOptions()

Return the current dictionary of :option:-X options, similarly to :data:sys._xoptions. On error, NULL is returned and an exception is set.

.. versionadded:: 3.2

.. _processcontrol:

Process Control

.. c:function:: void Py_FatalError(const char *message)

.. index:: single: abort()

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 :c:func:abort is called which will attempt to produce a :file:core file.

.. c:function:: void Py_Exit(int status)

.. index:: single: Py_FinalizeEx() single: exit()

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

.. versionchanged:: 3.6 Errors from finalization no longer ignored.

.. c:function:: int Py_AtExit(void (*func) ())

.. index:: single: Py_FinalizeEx() single: cleanup functions

Register a cleanup function to be called by :c:func: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, :c:func: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.