内容简介
#include <unistd.h>
int setpgid(pid_t%uA0pid, pid_t%uA0pgid)%uA0
pid_t getpgid(pid_t%uA0pid)%uA0
int setpgrp(void)%uA0
pid_t getpgrp(void)
描述
setpgid() sets the process group ID of the process specified by%uA0pid%uA0to%uA0pgid. If%uA0pid%uA0is zero, the process ID of the current process is used. If%uA0pgid%uA0is zero, the process ID of the process specified by%uA0pid%uA0is used. If%uA0setpgid() is used to move a process from one process group to another (as is done by some shells when creating pipelines), both process groups must be part of the same session. In this case, the%uA0pgid%uA0specifies an existing process group to be joined and the session ID of that group must match the session ID of the joining process.getpgid() returns the process group ID of the process specified by%uA0pid. If%uA0pid%uA0is zero, the process ID of the current process is used.
The call%uA0setpgrp() is equivalent to%uA0setpgid(0,0).
Similarly,%uA0getpgrp() is equivalent to%uA0getpgid(0) . Each process group is a member of a session and each process is a member of the session of which its process group is a member.
Process groups are used for distribution of signals, and by terminals to arbitrate requests for their input: Processes that have the same process group as the terminal are foreground and may read, while others will block with a signal if they attempt to read. These calls are thus used by programs such as%uA0csh(1) to create process groups in implementing job control. The%uA0TIOCGPGRP%uA0and%uA0TIOCSPGRPꃊlls described intermios(3) are used to get/set the process group of the control terminal.
If a session has a controlling terminal, CLOCAL is not set and a hangup occurs, then the session leader is sent a SIGHUP. If the session leader exits, the SIGHUP signal will be sent to each process in the foreground process group of the controlling terminal.
If the exit of the process causes a process group to become orphaned, and if any member of the newly-orphaned process group is stopped, then a SIGHUP signal followed by a SIGCONT signal will be sent to each process in the newly-orphaned process group.
%uA0
返回值
On success,%uA0setpgid() and%uA0setpgrp() return zero. On error, -1 is returned, and%uA0errno%uA0is set appropriately.getpgid() returns a process group on success. On error, -1 is returned, and%uA0errno%uA0is set appropriately.
getpgrp() always returns the current process group.
错误
| 标签 | 描述 |
|---|---|
| EACCES | An attempt was made to change the process group ID of one of the children of the calling process and the child had already performed an%uA0execve() (setpgid(),%uA0setpgrp()). |
| EINVAL | pgid%uA0is less than 0 (setpgid(),%uA0setpgrp()). |
| EPERM | An attempt was made to move a process into a process group in a different session, or to change the process group ID of one of the children of the calling process and the child was in a different session, or to change the process group ID of a session leader (setpgid(),%uA0setpgrp()). |
| ESRCH | For%uA0getpgid():%uA0pid%uA0does not match any process. For%uA0setpgid():%uA0pidis not the current process and not a child of the current process. |
遵循于
The functions%uA0setpgid() and%uA0getpgrp() conform to POSIX.1-2001. The function%uA0setpgrp() is from 4.2BSD. The function%uA0getpgid() conforms to SVr4.注意
A child created via%uA0fork(2) inherits its parent’s process group ID. The process group ID is preserved across an%uA0execve(2).POSIX took%uA0setpgid() from the BSD function%uA0setpgrp(). Also System V has a function with the same name, but it is identical to%uA0setsid(2).
To get the prototypes under glibc, define both _XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED, or use "#define _XOPEN_SOURCE%uA0n" for some integer%uA0nlarger than or equal to 500.
另请参阅
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