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author | Georg Brandl <georg@python.org> | 2022-11-28 09:41:24 (GMT) |
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committer | GitHub <noreply@github.com> | 2022-11-28 09:41:24 (GMT) |
commit | 492dc02b01828f346dd62412fefc654e781de923 (patch) | |
tree | 28bf03ddddf6a8a1acbe40869d84e260582295d5 /Doc/library | |
parent | 219696abb240607d3f807853c4c180825e60716e (diff) | |
download | cpython-492dc02b01828f346dd62412fefc654e781de923.zip cpython-492dc02b01828f346dd62412fefc654e781de923.tar.gz cpython-492dc02b01828f346dd62412fefc654e781de923.tar.bz2 |
bpo-41825: restructure docs for the os.wait*() family (GH-22356)
Diffstat (limited to 'Doc/library')
-rw-r--r-- | Doc/library/os.rst | 235 |
1 files changed, 142 insertions, 93 deletions
diff --git a/Doc/library/os.rst b/Doc/library/os.rst index 775aa32..b06f9bb 100644 --- a/Doc/library/os.rst +++ b/Doc/library/os.rst @@ -4491,6 +4491,9 @@ written in Python, such as a mail server's external command delivery program. number is zero); the high bit of the low byte is set if a core file was produced. + If there are no children that could be waited for, :exc:`ChildProcessError` + is raised. + :func:`waitstatus_to_exitcode` can be used to convert the exit status into an exit code. @@ -4498,76 +4501,40 @@ written in Python, such as a mail server's external command delivery program. .. seealso:: - :func:`waitpid` can be used to wait for the completion of a specific - child process and has more options. + The other :func:`!wait*` functions documented below can be used to wait for the + completion of a specific child process and have more options. + :func:`waitpid` is the only one also available on Windows. -.. function:: waitid(idtype, id, options, /) - Wait for the completion of one or more child processes. - *idtype* can be :data:`P_PID`, :data:`P_PGID`, :data:`P_ALL`, or - :data:`P_PIDFD` on Linux. - *id* specifies the pid to wait on. - *options* is constructed from the ORing of one or more of :data:`WEXITED`, - :data:`WSTOPPED` or :data:`WCONTINUED` and additionally may be ORed with - :data:`WNOHANG` or :data:`WNOWAIT`. The return value is an object - representing the data contained in the :c:type:`siginfo_t` structure, namely: - :attr:`si_pid`, :attr:`si_uid`, :attr:`si_signo`, :attr:`si_status`, - :attr:`si_code` or ``None`` if :data:`WNOHANG` is specified and there are no - children in a waitable state. - - .. availability:: Unix, not Emscripten, not WASI. - - .. versionadded:: 3.3 - -.. data:: P_PID - P_PGID - P_ALL - - These are the possible values for *idtype* in :func:`waitid`. They affect - how *id* is interpreted. - - .. availability:: Unix, not Emscripten, not WASI. - - .. versionadded:: 3.3 - -.. data:: P_PIDFD - - This is a Linux-specific *idtype* that indicates that *id* is a file - descriptor that refers to a process. - - .. availability:: Linux >= 5.4 - - .. versionadded:: 3.9 - -.. data:: WEXITED - WSTOPPED - WNOWAIT +.. function:: waitid(idtype, id, options, /) - Flags that can be used in *options* in :func:`waitid` that specify what - child signal to wait for. + Wait for the completion of a child process. - .. availability:: Unix, not Emscripten, not WASI. + *idtype* can be :data:`P_PID`, :data:`P_PGID`, :data:`P_ALL`, or (on Linux) :data:`P_PIDFD`. + The interpretation of *id* depends on it; see their individual descriptions. - .. versionadded:: 3.3 + *options* is an OR combination of flags. At least one of :data:`WEXITED`, + :data:`WSTOPPED` or :data:`WCONTINUED` is required; + :data:`WNOHANG` and :data:`WNOWAIT` are additional optional flags. + The return value is an object representing the data contained in the + :c:type:`!siginfo_t` structure with the following attributes: -.. data:: CLD_EXITED - CLD_KILLED - CLD_DUMPED - CLD_TRAPPED - CLD_STOPPED - CLD_CONTINUED + * :attr:`!si_pid` (process ID) + * :attr:`!si_uid` (real user ID of the child) + * :attr:`!si_signo` (always :data:`~signal.SIGCHLD`) + * :attr:`!si_status` (the exit status or signal number, depending on :attr:`!si_code`) + * :attr:`!si_code` (see :data:`CLD_EXITED` for possible values) - These are the possible values for :attr:`si_code` in the result returned by - :func:`waitid`. + If :data:`WNOHANG` is specified and there are no matching children in the + requested state, ``None`` is returned. + Otherwise, if there are no matching children + that could be waited for, :exc:`ChildProcessError` is raised. .. availability:: Unix, not Emscripten, not WASI. .. versionadded:: 3.3 - .. versionchanged:: 3.9 - Added :data:`CLD_KILLED` and :data:`CLD_STOPPED` values. - .. function:: waitpid(pid, options, /) @@ -4585,8 +4552,11 @@ written in Python, such as a mail server's external command delivery program. ``-1``, status is requested for any process in the process group ``-pid`` (the absolute value of *pid*). - An :exc:`OSError` is raised with the value of errno when the syscall - returns -1. + *options* is an OR combination of flags. If it contains :data:`WNOHANG` and + there are no matching children in the requested state, ``(0, 0)`` is + returned. Otherwise, if there are no matching children that could be waited + for, :exc:`ChildProcessError` is raised. Other options that can be used are + :data:`WUNTRACED` and :data:`WCONTINUED`. On Windows: Wait for completion of a process given by process handle *pid*, and return a tuple containing *pid*, and its exit status shifted left by 8 bits @@ -4599,7 +4569,7 @@ written in Python, such as a mail server's external command delivery program. :func:`waitstatus_to_exitcode` can be used to convert the exit status into an exit code. - .. availability:: Unix, not Emscripten, not WASI. + .. availability:: Unix, Windows, not Emscripten, not WASI. .. versionchanged:: 3.5 If the system call is interrupted and the signal handler does not raise an @@ -4612,9 +4582,9 @@ written in Python, such as a mail server's external command delivery program. Similar to :func:`waitpid`, except no process id argument is given and a 3-element tuple containing the child's process id, exit status indication, and resource usage information is returned. Refer to - :mod:`resource`.\ :func:`~resource.getrusage` for details on resource usage - information. The option argument is the same as that provided to - :func:`waitpid` and :func:`wait4`. + :func:`resource.getrusage` for details on resource usage information. The + *options* argument is the same as that provided to :func:`waitpid` and + :func:`wait4`. :func:`waitstatus_to_exitcode` can be used to convert the exit status into an exitcode. @@ -4625,10 +4595,10 @@ written in Python, such as a mail server's external command delivery program. .. function:: wait4(pid, options) Similar to :func:`waitpid`, except a 3-element tuple, containing the child's - process id, exit status indication, and resource usage information is returned. - Refer to :mod:`resource`.\ :func:`~resource.getrusage` for details on - resource usage information. The arguments to :func:`wait4` are the same - as those provided to :func:`waitpid`. + process id, exit status indication, and resource usage information is + returned. Refer to :func:`resource.getrusage` for details on resource usage + information. The arguments to :func:`wait4` are the same as those provided + to :func:`waitpid`. :func:`waitstatus_to_exitcode` can be used to convert the exit status into an exitcode. @@ -4636,6 +4606,111 @@ written in Python, such as a mail server's external command delivery program. .. availability:: Unix, not Emscripten, not WASI. +.. data:: P_PID + P_PGID + P_ALL + P_PIDFD + + These are the possible values for *idtype* in :func:`waitid`. They affect + how *id* is interpreted: + + * :data:`!P_PID` - wait for the child whose PID is *id*. + * :data:`!P_PGID` - wait for any child whose progress group ID is *id*. + * :data:`!P_ALL` - wait for any child; *id* is ignored. + * :data:`!P_PIDFD` - wait for the child identified by the file descriptor + *id* (a process file descriptor created with :func:`pidfd_open`). + + .. availability:: Unix, not Emscripten, not WASI. + + .. note:: :data:`!P_PIDFD` is only available on Linux >= 5.4. + + .. versionadded:: 3.3 + .. versionadded:: 3.9 + The :data:`!P_PIDFD` constant. + + +.. data:: WCONTINUED + + This *options* flag for :func:`waitpid`, :func:`wait3`, :func:`wait4`, and + :func:`waitid` causes child processes to be reported if they have been + continued from a job control stop since they were last reported. + + .. availability:: Unix, not Emscripten, not WASI. + + +.. data:: WEXITED + + This *options* flag for :func:`waitid` causes child processes that have terminated to + be reported. + + The other ``wait*`` functions always report children that have terminated, + so this option is not available for them. + + .. availability:: Unix, not Emscripten, not WASI. + + .. versionadded:: 3.3 + + +.. data:: WSTOPPED + + This *options* flag for :func:`waitid` causes child processes that have been stopped + by the delivery of a signal to be reported. + + This option is not available for the other ``wait*`` functions. + + .. availability:: Unix, not Emscripten, not WASI. + + .. versionadded:: 3.3 + + +.. data:: WUNTRACED + + This *options* flag for :func:`waitpid`, :func:`wait3`, and :func:`wait4` causes + child processes to also be reported if they have been stopped but their + current state has not been reported since they were stopped. + + This option is not available for :func:`waitid`. + + .. availability:: Unix, not Emscripten, not WASI. + + +.. data:: WNOHANG + + This *options* flag causes :func:`waitpid`, :func:`wait3`, :func:`wait4`, and + :func:`waitid` to return right away if no child process status is available + immediately. + + .. availability:: Unix, not Emscripten, not WASI. + + +.. data:: WNOWAIT + + This *options* flag causes :func:`waitid` to leave the child in a waitable state, so that + a later :func:`!wait*` call can be used to retrieve the child status information again. + + This option is not available for the other ``wait*`` functions. + + .. availability:: Unix, not Emscripten, not WASI. + + +.. data:: CLD_EXITED + CLD_KILLED + CLD_DUMPED + CLD_TRAPPED + CLD_STOPPED + CLD_CONTINUED + + These are the possible values for :attr:`!si_code` in the result returned by + :func:`waitid`. + + .. availability:: Unix, not Emscripten, not WASI. + + .. versionadded:: 3.3 + + .. versionchanged:: 3.9 + Added :data:`CLD_KILLED` and :data:`CLD_STOPPED` values. + + .. function:: waitstatus_to_exitcode(status) Convert a wait status to an exit code. @@ -4668,32 +4743,6 @@ written in Python, such as a mail server's external command delivery program. .. versionadded:: 3.9 -.. data:: WNOHANG - - The option for :func:`waitpid` to return immediately if no child process status - is available immediately. The function returns ``(0, 0)`` in this case. - - .. availability:: Unix, not Emscripten, not WASI. - - -.. data:: WCONTINUED - - This option causes child processes to be reported if they have been continued - from a job control stop since their status was last reported. - - .. availability:: Unix, not Emscripten, not WASI. - - Some Unix systems. - - -.. data:: WUNTRACED - - This option causes child processes to be reported if they have been stopped but - their current state has not been reported since they were stopped. - - .. availability:: Unix, not Emscripten, not WASI. - - The following functions take a process status code as returned by :func:`system`, :func:`wait`, or :func:`waitpid` as a parameter. They may be used to determine the disposition of a process. |