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module Process

Index:

egid egid= euid euid= exit! fork getpgid getpgrp getpriority gid gid= kill pid ppid setpgid setpgrp setpriority setsid uid uid= wait wait2 waitpid waitpid2

The Process module is a collection of methods used to manipulate processes.

constants
PRIO_PGRP 1 Process Group priority.
PRIO_PROCESS 0 Process priority.
PRIO_USER 2 User priority.
WNOHANG 1 Do not block if no child has exited. Not available on all platforms.
WUNTRACED 2 Return stopped children as well. Not available on all platforms.

class methods
egid Process.egid -> aFixnum
Returns the effective group id for this process.

Process.egid -> 500

egid= Process.egid= aFixnum -> aFixnum
Sets the effective group id for this process.
euid Process.euid -> aFixnum
Returns the effective user id for this process.

Process.euid -> 501

euid= Process.euid= aFixnum
Sets the effective user id for this process. Not available on all platforms.
exit! Process.exit!( aFixnum=-1 )
Exits the process immediately. No exit handlers are run. aFixnum is returned to the underlying system as the exit status. 

Process.exit!(0)

fork Process.fork [{ block } ] -> aFixnum or nil
See Kernel::fork on page 420.
getpgid Process.getpgid( anInteger ) -> anInteger
Returns the process group id for the given process id. Not available on all platforms.

Process.getpgid(Process.ppid()) -> 26676

getpgrp Process.getpgrp -> anInteger
Returns the process group id for this process. Not available on all platforms.

Process.getpgid(0) -> 26676
Process.getpgrp -> 26676

getpriority Process.getpriority( aKind, anInteger ) -> aFixnum
Gets the scheduling priority for specified process, process group, or user. aKind indicates the kind of entity to find: one of Process::PRIO_PGRP, Process::PRIO_USER, or Process::PRIO_PROCESS. anInteger is an id indicating the particular process, process group, or user (an id of 0 means current). Lower priorities are more favorable for scheduling. Not available on all platforms.

Process.getpriority(Process::PRIO_USER, 0) -> 19
Process.getpriority(Process::PRIO_PROCESS, 0) -> 19

gid Process.gid -> aFixnum
Returns the group id for this process.

Process.gid -> 500

gid= Process.gid= aFixnum -> aFixnum
Sets the group id for this process.
kill Process.kill( aSignal, [aPid]+ ) -> aFixnum
Sends the given signal to the specified process id(s), or to the current process if aPid is zero. aSignal may be an integer signal number or a POSIX signal name (either with or without a SIG prefix). If aSignal is negative (or starts with a ``-'' sign), kills process groups instead of processes. Not all signals are available on all platforms. 

trap("SIGHUP") { close_then_exit }
Process.kill("SIGHUP", 0)

pid Process.pid -> aFixnum
Returns the process id of this process. Not available on all platforms.

Process.pid -> 27984

ppid Process.ppid -> aFixnum
Returns the process id of the parent of this process. Always returns 0 on NT. Not available on all platforms. 

print "I am ", Process.pid, "\n"
Process.fork { print "Dad is ", Process.ppid, "\n" }

produces: 

I am 27986
Dad is 27986

setpgid Process.setpgid( aPid, anInteger ) -> 0
Sets the process group id of aPid (0 indicates this process) to anInteger. Not available on all platforms.
setpgrp Process.setpgrp -> 0
Equivalent to setpgid(0,0). Not available on all platforms.
setpriority Process.setpriority( kind, anInteger, anIntPriority ) -> 0
See Process#getpriority.

Process.setpriority(Process::PRIO_USER, 0, 19) -> 0
Process.setpriority(Process::PRIO_PROCESS, 0, 19) -> 0
Process.getpriority(Process::PRIO_USER, 0) -> 19
Process.getpriority(Process::PRIO_PROCESS, 0) -> 19

setsid Process.setsid -> aFixnum
Establishes this process as a new session and process group leader, with no controlling tty. Returns the session id. Not available on all platforms.

Process.setsid -> 27991

uid Process.uid -> aFixnum
Returns the user id of this process.

Process.uid -> 501

uid= Process.uid= anInteger -> aNumeric
Sets the (integer) user id for this process. Not available on all platforms.
wait Process.wait -> aFixnum
Waits for any child process to exit and returns the process id of that child. Raises a SystemError if there are no child processes. Not available on all platforms.

Process.fork { exit 1; } -> 27996
Process.wait -> 27996

wait2 Process.wait2 -> anArray
Waits for any child process to exit and returns an array containing the process id and the exit status of that child. Raises a SystemError if there are no child processes.

Process.fork { exit 1 } -> 27999
Process.wait2 -> [27999, 256]

waitpid Process.waitpid( aPid, anInteger=0 ) -> aPid
Waits for the given child process to exit. anInteger may be a logical or of the flag value Process::WNOHANG (do not block if no child available) or Process::WUNTRACED (return stopped children that haven't been reported). Not all flags are available on all platforms, but a flag value of zero will work on all platforms.

include Process
pid = fork { sleep 3 } -> 28002
Time.now -> Wed Feb 07 12:37:05 CST 2001
waitpid(pid, Process::WNOHANG) -> nil
Time.now -> Wed Feb 07 12:37:05 CST 2001
waitpid(pid, 0) -> 28002
Time.now -> Wed Feb 07 12:37:08 CST 2001

waitpid2 Process.waitpid2( aPid, anInteger=0 ) -> anArray
Waits for the given child process to exit, returning that child's process id and exit status. anInteger may be a logical or of the flag value Process::WNOHANG (do not block if no child available) or Process::WUNTRACED (return stopped children that haven't been reported). Not all flags are available on all platforms, but a flag value of zero will work on all platforms.

Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide"
Copyright © 2000 Addison Wesley Longman, Inc. Released under the terms of the Open Publication License V1.0.
This reference is available for download.