Processes

forkProcess corresponds to the POSIX fork system call. The IO action passed as an argument is executed in the child process; no other threads will be copied to the child process. On success, forkProcess returns the child's ProcessID to the parent process; in case of an error, an exception is thrown.

The exception masking state of the executed action is inherited (c.f. forkIO), see also forkProcessWithUnmask (since: 2.7.0.0).

forkProcess comes with a giant warning: since any other running threads are not copied into the child process, it's easy to go wrong: e.g. by accessing some shared resource that was held by another thread in the parent.

GHC note: forkProcess is not currently very well supported when using multiple capabilities (+RTS -N), although it is supported with -threaded as long as only one capability is being used.

Variant of forkProcess in the style of forkIOWithUnmask.

Since: 2.7.0.0

executeFile cmd args env calls one of the execv* family, depending on whether or not the current PATH is to be searched for the command, and whether or not an environment is provided to supersede the process's current environment. The basename (leading directory names suppressed) of the command is passed to execv* as arg[0]; the argument list passed to executeFile therefore begins with arg[1].

exitImmediately status calls _exit to terminate the process with the indicated exit status. The operation never returns. Since it does not use the Haskell exception system and it cannot be caught.

Note: Prior to unix-2.8.0.0 the type-signature of exitImmediately was ExitCode -> IO ().

Since: 2.8.0.0

getProcessID calls getpid to obtain the ProcessID for the current process.

getParentProcessID calls getppid to obtain the ProcessID for the parent of the current process.

getProcessGroupID calls getpgrp to obtain the ProcessGroupID for the current process.

getProcessGroupIDOf pid calls getpgid to obtain the ProcessGroupID for process pid.

createProcessGroupFor pid calls setpgid to make process pid a new process group leader.

joinProcessGroup pgid calls setpgid to set the ProcessGroupID of the current process to pgid.

setProcessGroupIDOf pid pgid calls setpgid to set the ProcessGroupIDOf for process pid to pgid.

createSession calls setsid to create a new session with the current process as session leader.

getProcessTimes calls times to obtain time-accounting information for the current process and its children.

The exit status of a process

getProcessStatus blk stopped pid calls waitpid, returning Just tc, the ProcessStatus for process pid if it is available, Nothing otherwise. If blk is False, then WNOHANG is set in the options for waitpid, otherwise not. If stopped is True, then WUNTRACED is set in the options for waitpid, otherwise not.

getAnyProcessStatus blk stopped calls waitpid, returning Just (pid, tc), the ProcessID and ProcessStatus for any child process if a child process has exited, or Nothing if there are child processes but none have exited. If there are no child processes, then getAnyProcessStatus raises an isDoesNotExistError exception.

If blk is False, then WNOHANG is set in the options for waitpid, otherwise not. If stopped is True, then WUNTRACED is set in the options for waitpid, otherwise not.

getGroupProcessStatus blk stopped pgid calls waitpid, returning Just (pid, tc), the ProcessID and ProcessStatus for any process in group pgid if one is available, or Nothing if there are child processes but none have exited. If there are no child processes, then getGroupProcessStatus raises an isDoesNotExistError exception.

If blk is False, then WNOHANG is set in the options for waitpid, otherwise not. If stopped is True, then WUNTRACED is set in the options for waitpid, otherwise not.

createProcessGroup pid calls setpgid to make process pid a new process group leader. This function is currently deprecated, and might be changed to making the current process a new process group leader in future versions.

setProcessGroupID pid pgid calls setpgid to set the ProcessGroupID for process pid to pgid. This function is currently deprecated, and might be changed to setting the ProcessGroupID for the current process in future versions.