R : Copyright 2005, The R Foundation for Statistical Computing
Version 2.1.1  (2005-06-20), ISBN 3-900051-07-0

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> ### * <HEADER>
> ###
> attach(NULL, name = "CheckExEnv")
> assign(".CheckExEnv", as.environment(2), pos = length(search())) # base
> ## add some hooks to label plot pages for base and grid graphics
> setHook("plot.new", ".newplot.hook")
> setHook("persp", ".newplot.hook")
> setHook("grid.newpage", ".gridplot.hook")
> 
> assign("cleanEx",
+        function(env = .GlobalEnv) {
+ 	   rm(list = ls(envir = env, all.names = TRUE), envir = env)
+            RNGkind("default", "default")
+ 	   set.seed(1)
+    	   options(warn = 1)
+ 	   delayedAssign("T", stop("T used instead of TRUE"),
+ 		  assign.env = .CheckExEnv)
+ 	   delayedAssign("F", stop("F used instead of FALSE"),
+ 		  assign.env = .CheckExEnv)
+ 	   sch <- search()
+ 	   newitems <- sch[! sch %in% .oldSearch]
+ 	   for(item in rev(newitems))
+                eval(substitute(detach(item), list(item=item)))
+ 	   missitems <- .oldSearch[! .oldSearch %in% sch]
+ 	   if(length(missitems))
+ 	       warning("items ", paste(missitems, collapse=", "),
+ 		       " have been removed from the search path")
+        },
+        env = .CheckExEnv)
> assign("..nameEx", "__{must remake R-ex/*.R}__", env = .CheckExEnv) # for now
> assign("ptime", proc.time(), env = .CheckExEnv)
> grDevices::postscript("fork-Examples.ps")
> assign("par.postscript", graphics::par(no.readonly = TRUE), env = .CheckExEnv)
> options(contrasts = c(unordered = "contr.treatment", ordered = "contr.poly"))
> options(warn = 1)    
> library('fork')
> 
> assign(".oldSearch", search(), env = .CheckExEnv)
> assign(".oldNS", loadedNamespaces(), env = .CheckExEnv)
> cleanEx(); ..nameEx <- "exit"
> 
> ### * exit
> 
> flush(stderr()); flush(stdout())
> 
> ### Name: exit
> ### Title: Exit from a child process
> ### Aliases: exit
> ### Keywords: programming
> 
> ### ** Examples
> 
> waittest <- function()
+ { 
+   pid = fork(NULL)
+   if(pid==0)
+     {
+       cat("Hi, I'm the child process and I need to explicitly call exit().")
+       cat("\n\n")
+       exit()
+     }
+   else
+     {
+       wait(pid)
+       cat("Hi, I'm the main process, and I wait()ed until the child process\n")
+       cat("finished before introducing myself.\n")
+     }
+ }
> 
> waittest()
Hi, I'm the child process and I need to explicitly call exit().

> 
> ### Name: exit
> ### Title: Exit from a child process
> ### Aliases: exit
> ### Keywords: programming
> 
> ### ** Examples
> 
> waittest <- function()
+ { 
+   pid = fork(NULL)
+   if(pid==0)
+     {
+       cat("Hi, I'm the child process and I need to explicitly call exit().")
+       cat("\n\n")
+       exit()
+     }
+   else
+     {
+       wait(pid)
+       cat("Hi, I'm the main process, and I wait()ed until the child process\n")
+       cat("finished before introducing myself.\n")
+     }
+ }
> 
> waittest()
Hi, I'm the main process, and I wait()ed until the child process
finished before introducing myself.
> 
> 
> 
> cleanEx(); ..nameEx <- "fork"
> 
> ### * fork
> 
> flush(stderr()); flush(stdout())
> 
> ### Name: fork
> ### Title: Create a new R process using the Unix 'fork' system call
> ### Aliases: fork
> ### Keywords: programming
> 
> ### ** Examples
> 
> 
> ###
> # Count from 1 to 10 in a separate process
> ###
> 
> # define the function to do the work
> testfun <- function()
+   {
+     cat("Counting in process", getpid(), "\n")
+     for(i in 1:10)
+       {
+         i <<- i+1  # assign into Global environment
+         cat("i=",i,"\n")
+       }
+     cat("Done counting in process", getpid(), "\n")
+   }
> 
> # run normally, the function will change our value of i
> i <- 0
> testfun()
Counting in process 1581 
i= 1 
i= 2 
i= 3 
i= 4 
i= 5 
i= 6 
i= 7 
i= 8 
i= 9 
i= 10 
Done counting in process 1581 
> i 
[1] 11
> 
> # Run in a separate process, our value of i remains unchanged
> i <- 0
> {
+   pid <- fork(testfun)
+   wait(pid) # wait until the child finishes, then display its exit status
+ }
Counting in process 1586 
i= 1 
i= 2 
i= 3 
i= 4 
i= 5 
i= 6 
i= 7 
i= 8 
i= 9 
i= 10 
Done counting in process 1586 
> 
> # Run in a separate process, our value of i remains unchanged
> i <- 0
> {
+   pid <- fork(testfun)
+   wait(pid) # wait until the child finishes, then display its exit status
+ }
   pid status 
  1586      0 
>  
> 
> ###
> # Use a socket to communicate between two processes.  Information
> # typed on the console, which is read by the initial process, will be send
> # to the child process for display. 
> ###
> ## Not run: 
> ##D send <- function()
> ##D   {
> ##D      pid <- getpid()
> ##D      con1 <- socketConnection(Sys.info()["nodename"], port = 6011)
> ##D      i <- 1
> ##D      while(TRUE)
> ##D        {
> ##D          cat("[",pid,"] ",i,": ",sep="")
> ##D          data <- readLines(stdin(), n=1)
> ##D          writeLines(data, con=con1)
> ##D          if( length(grep("quit", data))>0 )
> ##D             break;
> ##D          i <- i+1
> ##D        }
> ##D      close(con1)
> ##D   }
> ##D 
> ##D recieve <- function()
> ##D   {
> ##D      pid <- getpid()
> ##D      con2 <- socketConnection(port = 6011, block=TRUE, server=TRUE)
> ##D      i <- 1
> ##D      while(TRUE)
> ##D        {
> ##D           data <- readLines(con2, n=1)
> ##D           cat("[",pid,"] ",i,": ",sep="")
> ##D           writeLines(data, stdout())
> ##D           if( length(grep("quit", data))>0 )
> ##D               break;
> ##D           i <- i+1
> ##D        }
> ##D      close(con2)
> ##D   }
> ##D 
> ##D pid <- fork(recieve)
> ##D send()
> ## End(Not run)
> 
> 
> 
> cleanEx(); ..nameEx <- "getpid"
> 
> ### * getpid
> 
> flush(stderr()); flush(stdout())
> 
> ### Name: getpid
> ### Title: Obtain the process id for the current process.
> ### Aliases: getpid
> ### Keywords: programming
> 
> ### ** Examples
> 
> 
> getpid()
[1] 1581
> 
> ## Not run: 
> ##D for(i in 1:10)
> ##D   fork( function() { cat("PID:", getpid(), "\n"); exit()} )
> ## End(Not run)
> 
> 
> 
> cleanEx(); ..nameEx <- "kill"
> 
> ### * kill
> 
> flush(stderr()); flush(stdout())
> 
> ### Name: kill
> ### Title: Send a signal to one or more processes.
> ### Aliases: kill killall
> ### Keywords: programming
> 
> ### ** Examples
> 
> 
>    # start a process that just sleeps for 10 seconds
>     sleepy <- function() 
+      {
+        cat("Going to sleep..")
+        Sys.sleep(10)
+        cat("Woke up!")
+      }
>    pid <- fork( sleepy )
> 
>    # kill the sleeping process
>    kill(pid)
[1] 0
> 
> 
> 
> 
> cleanEx(); ..nameEx <- "signame"
> 
> ### * signame
> 
> flush(stderr()); flush(stdout())
> 
> ### Name: signame
> ### Title: Obtain information about signals
> ### Aliases: signame sigval siglist
> ### Keywords: programming
> 
> ### ** Examples
> 
> 
>    # look up the numeric value for SIGABT:
>    sigval("SIGKILL")
     name       val      desc 
"SIGKILL"       "9"  "Killed" 
> 
>    # the 'SIG' component can be ommitted:
>    sigval("HUP")
    name      val     desc 
"SIGHUP"      "1" "Hangup" 
> 
>    # now look up based on value
>    signame(9)
     name       val      desc 
"SIGKILL"       "9"  "Killed" 
> 
>    # and get a complete table of signal information
>    siglist()
   name       val                                       desc
1     1    SIGHUP                                     Hangup
2     2    SIGINT                                  Interrupt
3     3   SIGQUIT                                       Quit
4     4    SIGILL                        Illegal Instruction
5     5   SIGTRAP                   Trace or Breakpoint Trap
6     6   SIGABRT                                      Abort
7     7    SIGEMT                             Emulation Trap
8     8    SIGFPE                       Arithmetic Exception
9     9   SIGKILL                                     Killed
10   10    SIGBUS                                  Bus Error
11   11   SIGSEGV                         Segmentation Fault
12   12    SIGSYS                            Bad System Call
13   13   SIGPIPE                                Broken Pipe
14   14   SIGALRM                                Alarm Clock
15   15   SIGTERM                                 Terminated
16   30   SIGUSR1                              User Signal 1
17   31   SIGUSR2                              User Signal 2
18   20   SIGCHLD                       Child Status Changed
19   28  SIGWINCH                         Window Size Change
20   16    SIGURG                    Urgent Socket Condition
21   17   SIGSTOP                           Stopped (Signal)
22   18   SIGTSTP                             Stopped (User)
23   19   SIGCONT                                  Continued
24   21   SIGTTIN                        Stopped (tty input)
25   22   SIGTTOU                       Stopped (tty output)
26   26 SIGVTALRM                      Virtual Timer Expired
27   27   SIGPROF                    Profiling Timer Expired
28   24   SIGXCPU                    CPU Time limit Exceeded
29   25   SIGXFSZ                   File Size Limit Exceeded
30    6    SIGIOT            IOT trap. (Synonym for SIGABRT)
31   23     SIGIO                 I/O Now Possible (4.2 BSD}
32   29   SIGINFO Power Fail or Restart (Synonym for SIGPWR}
> 
> 
> 
> cleanEx(); ..nameEx <- "wait"
> 
> ### * wait
> 
> flush(stderr()); flush(stdout())
> 
> ### Name: wait
> ### Title: Wait for child process(es) to stop or terminate.
> ### Aliases: wait
> ### Keywords: programming
> 
> ### ** Examples
> 
> waittest <- function()
+ { 
+   pid = fork(NULL)
+   if(pid==0)
+     {
+       cat("Hi, I'm the child process and I need to explicitly call exit().")
+       cat("\n\n")
+       exit()
+     }
+   else
+     {
+       wait(pid)
+       cat("Hi, I'm the main process, and I wait()ed until the child process\n")
+       cat("finished before introducing myself.\n")
+     }
+ }
> 
> waittest()
Hi, I'm the child process and I need to explicitly call exit().

> 
> ### Name: wait
> ### Title: Wait for child process(es) to stop or terminate.
> ### Aliases: wait
> ### Keywords: programming
> 
> ### ** Examples
> 
> waittest <- function()
+ { 
+   pid = fork(NULL)
+   if(pid==0)
+     {
+       cat("Hi, I'm the child process and I need to explicitly call exit().")
+       cat("\n\n")
+       exit()
+     }
+   else
+     {
+       wait(pid)
+       cat("Hi, I'm the main process, and I wait()ed until the child process\n")
+       cat("finished before introducing myself.\n")
+     }
+ }
> 
> waittest()
Hi, I'm the main process, and I wait()ed until the child process
finished before introducing myself.
> 
> 
> 
> ### * <FOOTER>
> ###
> cat("Time elapsed: ", proc.time() - get("ptime", env = .CheckExEnv),"\n")
Time elapsed:  0.08 0.07 0.19 0 0.03 
> grDevices::dev.off()
null device 
          1 
> ###
> ### Local variables: ***
> ### mode: outline-minor ***
> ### outline-regexp: "\\(> \\)?### [*]+" ***
> ### End: ***
> quit('no')