| Module | Process |
| In: |
process.c
|
The Process module is a collection of methods used to manipulate processes.
| WNOHANG | = | INT2FIX(WNOHANG) |
| WNOHANG | = | INT2FIX(0) |
| WUNTRACED | = | INT2FIX(WUNTRACED) |
| WUNTRACED | = | INT2FIX(0) |
| PRIO_PROCESS | = | INT2FIX(PRIO_PROCESS) |
| PRIO_PGRP | = | INT2FIX(PRIO_PGRP) |
| PRIO_USER | = | INT2FIX(PRIO_USER) |
Terminate execution immediately, effectively by calling Kernel.exit(1). If msg is given, it is written to STDERR prior to terminating.
Initiates the termination of the Ruby script by raising the SystemExit exception. This exception may be caught. The optional parameter is used to return a status code to the invoking environment.
begin
exit
puts "never get here"
rescue SystemExit
puts "rescued a SystemExit exception"
end
puts "after begin block"
produces:
rescued a SystemExit exception after begin block
Just prior to termination, Ruby executes any at_exit functions (see Kernel::at_exit) and runs any object finalizers (see ObjectSpace::define_finalizer).
at_exit { puts "at_exit function" }
ObjectSpace.define_finalizer("string", proc { puts "in finalizer" })
exit
produces:
at_exit function in finalizer
Exits the process immediately. No exit handlers are run. fixnum is returned to the underlying system as the exit status.
Process.exit!(0)
Creates a subprocess. If a block is specified, that block is run in the subprocess, and the subprocess terminates with a status of zero. Otherwise, the fork call returns twice, once in the parent, returning the process ID of the child, and once in the child, returning nil. The child process can exit using Kernel.exit! to avoid running any at_exit functions. The parent process should use Process.wait to collect the termination statuses of its children or use Process.detach to register disinterest in their status; otherwise, the operating system may accumulate zombie processes.
The thread calling fork is the only thread in the created child process. fork doesn’t copy other threads.
Some operating systems retain the status of terminated child processes until the parent collects that status (normally using some variant of wait(). If the parent never collects this status, the child stays around as a zombie process. Process::detach prevents this by setting up a separate Ruby thread whose sole job is to reap the status of the process pid when it terminates. Use detach only when you do not intent to explicitly wait for the child to terminate. detach only checks the status periodically (currently once each second).
In this first example, we don’t reap the first child process, so it appears as a zombie in the process status display.
p1 = fork { sleep 0.1 }
p2 = fork { sleep 0.2 }
Process.waitpid(p2)
sleep 2
system("ps -ho pid,state -p #{p1}")
produces:
27389 Z
In the next example, Process::detach is used to reap the child automatically.
p1 = fork { sleep 0.1 }
p2 = fork { sleep 0.2 }
Process.detach(p1)
Process.waitpid(p2)
sleep 2
system("ps -ho pid,state -p #{p1}")
(produces no output)
Returns the effective group ID for this process. Not available on all platforms.
Process.egid #=> 500
Returns the process group ID for the given process id. Not available on all platforms.
Process.getpgid(Process.ppid()) #=> 25527
Returns the process group ID for this process. Not available on all platforms.
Process.getpgid(0) #=> 25527 Process.getpgrp #=> 25527
Gets the scheduling priority for specified process, process group, or user. kind indicates the kind of entity to find: one of Process::PRIO_PGRP, Process::PRIO_USER, or Process::PRIO_PROCESS. integer 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
Get an Array of the gids of groups in the supplemental group access list for this process.
Process.groups #=> [27, 6, 10, 11]
Initializes the supplemental group access list by reading the system group database and using all groups of which the given user is a member. The group with the specified gid is also added to the list. Returns the resulting Array of the gids of all the groups in the supplementary group access list. Not available on all platforms.
Process.groups #=> [0, 1, 2, 3, 4, 6, 10, 11, 20, 26, 27] Process.initgroups( "mgranger", 30 ) #=> [30, 6, 10, 11] Process.groups #=> [30, 6, 10, 11]
Sends the given signal to the specified process id(s), or to the current process if pid is zero. signal may be an integer signal number or a POSIX signal name (either with or without a SIG prefix). If signal is negative (or starts with a minus sign), kills process groups instead of processes. Not all signals are available on all platforms.
pid = fork do
Signal.trap("HUP") { puts "Ouch!"; exit }
# ... do some work ...
end
# ...
Process.kill("HUP", pid)
Process.wait
produces:
Ouch!
Returns the maximum number of gids allowed in the supplemental group access list.
Process.maxgroups #=> 32
Returns the process id of the parent of this process. Always returns 0 on NT. Not available on all platforms.
puts "I am #{Process.pid}"
Process.fork { puts "Dad is #{Process.ppid}" }
produces:
I am 27417 Dad is 27417
Sets the process group ID of pid (0 indicates this process) to integer. Not available on all platforms.
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
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 #=> 27422
Returns a Tms structure (see Struct::Tms on page 388) that contains user and system CPU times for this process.
t = Process.times [ t.utime, t.stime ] #=> [0.0, 0.02]
Waits for a child process to exit, returns its process id, and sets $? to a Process::Status object containing information on that process. Which child it waits on depends on the value of pid:
| > 0: | Waits for the child whose process ID equals pid. |
| 0: | Waits for any child whose process group ID equals that of the calling process. |
| -1: | Waits for any child process (the default if no pid is given). |
| < -1: | Waits for any child whose process group ID equals the absolute value of pid. |
The flags argument may be a logical or of the flag values 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.
Calling this method raises a SystemError if there are no child processes. Not available on all platforms.
include Process
fork { exit 99 } #=> 27429
wait #=> 27429
$?.exitstatus #=> 99
pid = fork { sleep 3 } #=> 27440
Time.now #=> Wed Apr 09 08:57:09 CDT 2003
waitpid(pid, Process::WNOHANG) #=> nil
Time.now #=> Wed Apr 09 08:57:09 CDT 2003
waitpid(pid, 0) #=> 27440
Time.now #=> Wed Apr 09 08:57:12 CDT 2003
Waits for a child process to exit (see Process::waitpid for exact semantics) and returns an array containing the process id and the exit status (a Process::Status object) of that child. Raises a SystemError if there are no child processes.
Process.fork { exit 99 } #=> 27437
pid, status = Process.wait2
pid #=> 27437
status.exitstatus #=> 99
Waits for all children, returning an array of pid/status pairs (where status is a Process::Status object).
fork { sleep 0.2; exit 2 } #=> 27432
fork { sleep 0.1; exit 1 } #=> 27433
fork { exit 0 } #=> 27434
p Process.waitall
produces:
[[27434, #<Process::Status: pid=27434,exited(0)>],
[27433, #<Process::Status: pid=27433,exited(1)>],
[27432, #<Process::Status: pid=27432,exited(2)>]]
Waits for a child process to exit, returns its process id, and sets $? to a Process::Status object containing information on that process. Which child it waits on depends on the value of pid:
| > 0: | Waits for the child whose process ID equals pid. |
| 0: | Waits for any child whose process group ID equals that of the calling process. |
| -1: | Waits for any child process (the default if no pid is given). |
| < -1: | Waits for any child whose process group ID equals the absolute value of pid. |
The flags argument may be a logical or of the flag values 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.
Calling this method raises a SystemError if there are no child processes. Not available on all platforms.
include Process
fork { exit 99 } #=> 27429
wait #=> 27429
$?.exitstatus #=> 99
pid = fork { sleep 3 } #=> 27440
Time.now #=> Wed Apr 09 08:57:09 CDT 2003
waitpid(pid, Process::WNOHANG) #=> nil
Time.now #=> Wed Apr 09 08:57:09 CDT 2003
waitpid(pid, 0) #=> 27440
Time.now #=> Wed Apr 09 08:57:12 CDT 2003
Waits for a child process to exit (see Process::waitpid for exact semantics) and returns an array containing the process id and the exit status (a Process::Status object) of that child. Raises a SystemError if there are no child processes.
Process.fork { exit 99 } #=> 27437
pid, status = Process.wait2
pid #=> 27437
status.exitstatus #=> 99