process Class Reference

## Static Public Member Functions

static pid_t | getProcessId ()
static pid_t | getParentProcessId ()
static pid_t | getProcessGroupId ()
static pid_t | getProcessGroupId (pid_t pid)
static bool | setProcessGroupId ()
static bool | setProcessGroupId (pid_t pgid)
static bool | setProcessGroupId (pid_t pid, pid_t pgid)
static pid_t | getSessionId ()
static pid_t | getSessionId (pid_t pid)
static pid_t | newSession ()
static uid_t | getUserId ()
static uid_t | getEffectiveUserId ()
static bool | setUserId (uid_t uid)
static bool | setUser (const char *username)
static bool | setEffectiveUserId (uid_t uid)
static bool | setEffectiveUser (const char *username)
static bool | setRealAndEffectiveUserId (uid_t uid, uid_t euid)
static gid_t | getGroupId ()
static gid_t | getEffectiveGroupId ()
static bool | setGroupId (gid_t gid)
static bool | setGroup (const char *groupname)
static bool | setEffectiveGroupId (gid_t gid)
static bool | setEffectiveGroup (const char *groupname)
static bool | setRealAndEffectiveGroupId (gid_t gid, gid_t egid)
static mode_t | setFileCreationMask (mode_t mask)
static pid_t | fork ()
static bool | supportsFork ()
static bool | exec (const char *command, const char *const *args)
static pid_t | spawn (const char *command, const char *const *args, bool detached)
static bool | detach ()
static void | exit (int32_t status)
static void | exitImmediately (int32_t status)
static bool | sendSignal (pid_t processid, int32_t signum)
static bool | raiseSignal (int32_t signum)
static bool | atExit (void(*function)(void))
static void | exitOnCrashOrShutDown ()
static int64_t | checkForPidFile (const char *filename)
static bool | createPidFile (const char *filename, mode_t permissions)
static void | exitOnShutDown ()
static void | handleShutDown (void(*shutdownfunction)(int32_t))
static void | exitOnCrash ()
static void | handleCrash (void(*crashfunction)(int32_t))
static void | waitForChildren ()
static void | dontWaitForChildren ()
static bool | wait (pid_t pid)
static bool | wait (pid_t pid, int32_t *exitstatus)
static pid_t | getChildStateChange (pid_t pid, bool wait, bool ignorestop, bool ignorecontinue, childstatechange *newstate, int32_t *exitstatus, int32_t *signum, bool *coredump)
static bool | supportsGetChildStateChange ()
static void | retryFailedFork ()
static void | dontRetryFailedFork ()
static bool | getRetryFailedFork ()
static void | backtrace (output *out, uint32_t maxframes)
static void | backtrace (output *out)
static void | backtrace (const char *filename)
static void | backtrace (const char *filename, mode_t perms, uint32_t maxframes)

## Detailed Description

The process class provides static methods for accessing information about and controlling processes, including methods for forking, spawning and executing child processes.

## Member Function Documentation

## atExit()

static bool process::atExit | ( | void(*)(void) | function | ) |

static

Registers "function" to be called when the process exits normally. Returns true on success and false on failure.

## backtrace() [1/4]

static void process::backtrace | ( | const char * | filename | ) |

static

Appends the backtrace for the current thread to "filename".

A maximum of 128 stack frames will be included in the backtrace.

(Not supported on all platforms.)

## backtrace() [2/4]

static void process::backtrace | ( | const char * | filename,
|  | mode_t | perms,
|  | uint32_t | maxframes
| ) |  |

static

Appends the backtrace for the current thread to "filename".

If "filename" doesn't already exist then it will be created with "perms" permissions.

"maxframes" indicates the maximum number of stack frames to include in the backtrace.

(Not supported on all platforms.)

## backtrace() [3/4]

static void process::backtrace | ( | output * | out | ) |

static

Writes the backtrace for the current thread to "buffer".

A maximum of 128 stack frames will be included in the backtrace.

(Not supported on all platforms.)

## backtrace() [4/4]

static void process::backtrace | ( | output * | out,
|  | uint32_t | maxframes
| ) |  |

static

Writes the backtrace for the current thread to "buffer".

"maxframes" indicates the maximum number of stack frames to include in the backtrace.

(Not supported on all platforms.)

## checkForPidFile()

static int64_t process::checkForPidFile | ( | const char * | filename | ) |

static

Checks for filename "filename" and reads the process id out of it, if it exists. Returns the process id on success or -1 on failure.

## createPidFile()

static bool process::createPidFile | ( | const char * | filename,
|  | mode_t | permissions
| ) |  |

static

Create's file "filename" with permissions "permissions" and puts the current process id in it. Note that when you delete this file during shutdown you must use the full pathname since the process::detach() method changes directories to "/". Returns true on success and false on failure.

## detach()

static bool process::detach | ( |  | ) |

static

Detaches the current process from the controlling tty, creates a new session, changes directory to / and sets the file creation mask to 0. Use this method to "fork your process into the background." Returns true on success and false on failure.

## dontRetryFailedFork()

static void process::dontRetryFailedFork | ( |  | ) |

static

Causes fork() calls not to be automatically retried if they fail because of insufficient system resources. If set, if a fork() fails, the system error is set to EAGAIN and the fork() must be retried by the calling program.

## dontWaitForChildren()

static void process::dontWaitForChildren | ( |  | ) |

static

This method causes the process not to wait on child processes which have exited. Ordinarily, you'd want to wait on child processes, but this interferes with the behavior of WEXITSTATUS() after a call to system() (and possibly other calls). This method allows you to disable waiting on child processes.

## exec()

static bool process::exec | ( | const char * | command,
|  | const char *const * | args
| ) |  |

static

Runs "command" with arguments "args", replacing the current running process with this new process. Whether the new process retains the process id of the current process is platform-specific. Note that the first element of array "args" should be the name of the command that you want to run, typically the same as "command". "args" should be NULL terminated. Returns false if an error occurred and otherwise does not return at all.

## exit()

static void process::exit | ( | int32_t | status | ) |

static

Terminates the calling process and sets the exit status to "status".

## exitImmediately()

static void process::exitImmediately | ( | int32_t | status | ) |

static

Terminates the calling process "immediately" (without calling any functions registered to run at exit) and sets the exit status to "status".

## exitOnCrash()

static void process::exitOnCrash | ( |  | ) |

static

Sets up a default handler that exits cleanly if the process crashes with a program error signal - SIGABRT, SIGFPE, SIGILL, SIGSEGV, SIGBUS, SIGIOT, SIGEMT or SIGSYS. NOTE: The default handler calls waitForChildren() before exiting to prevent zombie processes.

## exitOnCrashOrShutDown()

static void process::exitOnCrashOrShutDown | ( |  | ) |

static

Calls exitOnShutDown(), exitOnCrash() and waitForChildren() below.

## exitOnShutDown()

static void process::exitOnShutDown | ( |  | ) |

static

Sets up a default handler that exits cleanly when the process is killed with a termination signal - SIGINT, SIGTERM, SIGQUIT or SIGHUP. NOTE: The default handler calls waitForChildren() before exiting to prevent zombie processes.

## fork()

static pid_t process::fork | ( |  | ) |

static

Creates a child process. The child is a duplicate of the parent inheriting file descriptors and a copy of the parent's address space. The child does not have access to the parent's address space. In the parent process, the process id of the child is returned. In the child process, 0 is returned. -1 is returned if an error occurred and no child is forked.

## getChildStateChange()

static pid_t process::getChildStateChange | ( | pid_t | pid,
|  | bool | wait,
|  | bool | ignorestop,
|  | bool | ignorecontinue,
|  | childstatechange * | newstate,
|  | int32_t * | exitstatus,
|  | int32_t * | signum,
|  | bool * | coredump
| ) |  |

static

This method causes the process to get information about a change in process state for the specified child process id "pid" (ie. whether it was stopped, continued or killed).

Returns the process id of the child that changed state, -1 if an error occurred, and 0 if "wait" is set false and no child has changed state.

Setting "pid" to -1 causes the method to get information on any child of the current process.

Waiting on child processes to exit prevents so-called "zombie" processes from occurring. However, this method only waits when called. To configure a process to automatically wait on and respond when any child process exits, use waitForChildren().

If "wait" is set true then the method waits until a child state-change occurs. Otherwise the method returns immediately.

If "ignorestop" is set true then the method ignores when a child process has been stopped.

If "ignorecontinue" is set true then the method ignores when a child process has been continued.

On exit, if "newstate" is non-NULL then it is populated with one of the members of the childstatechange enum, indicating the new state of the child process.

If "newstate" is EXIT_CHILDSTATECHANGE and "exitstatus" is non-null then "exitstatus" is populated with the exit status of the child process.

If "newstate" is TERMINATED_CHILDSTATECHANGE or STOPPED_CHILDSTATECHANGE and "signum" is non-null then "signum" is populated with the signum that terminated or stopped the child process.

If "newstate" is TERMINATED_CHILDSTATECHANGE and "coredump" is non-null then "coredump" is set true if a core dump was produced and false otherwise.

## getEffectiveGroupId()

static gid_t process::getEffectiveGroupId | ( |  | ) |

static

Returns the effective group id of the current process.

## getEffectiveUserId()

static uid_t process::getEffectiveUserId | ( |  | ) |

static

Returns the effective user id of the current process.

## getGroupId()

static gid_t process::getGroupId | ( |  | ) |

static

Returns the real group id of the current process.

## getParentProcessId()

static pid_t process::getParentProcessId | ( |  | ) |

static

Returns the process id of the parent process of the current process.

## getProcessGroupId() [1/2]

static pid_t process::getProcessGroupId | ( |  | ) |

static

Returns the process group id of the current process.

## getProcessGroupId() [2/2]

static pid_t process::getProcessGroupId | ( | pid_t | pid | ) |

static

Returns the process group id of the process pid.

## getProcessId()

static pid_t process::getProcessId | ( |  | ) |

static

Returns the process id of the current process.

## getRetryFailedFork()

static bool process::getRetryFailedFork | ( |  | ) |

static

Returns true if failed fork() calls will be retried and false otherwise.

## getSessionId() [1/2]

static pid_t process::getSessionId | ( |  | ) |

static

Returns the session id of the current process.

## getSessionId() [2/2]

static pid_t process::getSessionId | ( | pid_t | pid | ) |

static

Returns the session id of the process pid.

## getUserId()

static uid_t process::getUserId | ( |  | ) |

static

Returns the real user id of the current process.

## handleCrash()

static void process::handleCrash | ( | void(*)(int32_t) | crashfunction | ) |

static

Allows you to designate a function to run if the process crashes with a program error signal - SIGABRT, SIGFPE, SIGILL, SIGSEGV, SIGBUS, SIGIOT, SIGEMT or SIGSYS.

## handleShutDown()

static void process::handleShutDown | ( | void(*)(int32_t) | shutdownfunction | ) |

static

Allows you to designate a function to run when the process is killed with a termination signal - SIGINT, SIGTERM, SIGQUIT or SIGHUP.

## newSession()

static pid_t process::newSession | ( |  | ) |

static

Creates a new session, sets the calling process to be the process group leader and detaches from the controlling terminal. Returns the session id on success or -1 if an error occurred.

## raiseSignal()

static bool process::raiseSignal | ( | int32_t | signum | ) |

static

Send signal "signum" to self. Returns true on success and false on failure.

## retryFailedFork()

static void process::retryFailedFork | ( |  | ) |

static

Causes fork() calls to be automatically retried if they fail because of insufficient system resources. This is the default behavior. Otherwise, if a fork() fails, the system error is set to EAGAIN and the fork() must be retried by the calling program.

## sendSignal()

static bool process::sendSignal | ( | pid_t | processid,
|  | int32_t | signum
| ) |  |

static

Send signal "signum" to process "processid". Returns true on success and false on failure.

## setEffectiveGroup()

static bool process::setEffectiveGroup | ( | const char * | groupname | ) |

static

Sets the effective group id of the current process to the group id of "groupname". Does not set the real or saved group ids.

Returns true on success and false on failure.

## setEffectiveGroupId()

static bool process::setEffectiveGroupId | ( | gid_t | gid | ) |

static

Sets the effective group id of the current process to gid. Does not set the real or saved group ids.

Returns true on success and false on failure.

## setEffectiveUser()

static bool process::setEffectiveUser | ( | const char * | username | ) |

static

Sets the effective user id of the current process to the user id of "username". Does not set the real or saved user ids.

Returns true on success and false on failure.

## setEffectiveUserId()

static bool process::setEffectiveUserId | ( | uid_t | uid | ) |

static

Sets the effective user id of the current process to uid. Does not set the real or saved user ids.

Returns true on success and false on failure.

## setFileCreationMask()

static mode_t process::setFileCreationMask | ( | mode_t | mask | ) |

static

Set file/directory creation mode mask to "mask". Returns the mask that was previously in effect.

## setGroup()

static bool process::setGroup | ( | const char * | groupname | ) |

static

Sets the effective group id of the current process to the group id of "groupname". If the effective group id is root, the real and saved group ids are also set.

Returns true on success and false on failure.

## setGroupId()

static bool process::setGroupId | ( | gid_t | gid | ) |

static

Sets the effective group id of the current process to gid. If the effective group id is root, the real and saved group ids are also set.

Returns true on success and false on failure.

## setProcessGroupId() [1/3]

static bool process::setProcessGroupId | ( |  | ) |

static

Sets the process group id of the current process to the current process id.

## setProcessGroupId() [2/3]

static bool process::setProcessGroupId | ( | pid_t | pgid | ) |

static

Sets the process group id of the current process to pgid.

## setProcessGroupId() [3/3]

static bool process::setProcessGroupId | ( | pid_t | pid,
|  | pid_t | pgid
| ) |  |

static

Sets the process group id of the process pid to pgid.

## setRealAndEffectiveGroupId()

static bool process::setRealAndEffectiveGroupId | ( | gid_t | gid,
|  | gid_t | egid
| ) |  |

static

Sets the real group id of the current process to gid and the effective group id of the current process to egid. If the real group id is set or the effective group id is set to a value not equal to the previous real group id, the saved group id is set to the new effective group id.

Returns true on success and false on failure.

## setRealAndEffectiveUserId()

static bool process::setRealAndEffectiveUserId | ( | uid_t | uid,
|  | uid_t | euid
| ) |  |

static

Sets the real user id of the current process to uid and the effective user id of the current process to euid. If the real user id is set or the effective user id is set to a value not equal to the previous real user id, the saved user id is set to the new effective user id.

Returns true on success and false on failure.

## setUser()

static bool process::setUser | ( | const char * | username | ) |

static

Sets the effective user id of the current process to the user id of "username". If the effective user id is root, the real and saved user ids are also set.

Returns true on success and false on failure.

## setUserId()

static bool process::setUserId | ( | uid_t | uid | ) |

static

Sets the effective user id of the current process to uid. If the effective user id is root, the real and saved user ids are also set.

Returns true on success and false on failure.

## spawn()

static pid_t process::spawn | ( | const char * | command,
|  | const char *const * | args,
|  | bool | detached
| ) |  |

static

Runs "command" with arguments "args" as a new process. If "detached" is true then the process is started in the background. Use this instead of a combinination of fork() and exec() as it is more efficient on some platforms. Note that the first element of array "args" should be the name of the command that you want to run, typically the same as "command". "args" should be NULL terminated. Returns the process id of the child process or -1 if an error occurred.

## supportsFork()

static bool process::supportsFork | ( |  | ) |

static

Returns true of this platform supports fork() and false otherwise.

## supportsGetChildStateChange()

static bool process::supportsGetChildStateChange | ( |  | ) |

static

Returns true if the platform supports waiting for a child process to exit or change state and false otherwise.

## wait() [1/2]

static bool process::wait | ( | pid_t | pid | ) |

static

This methods causes the process to wait until child process "pid" exits. Returns true on success and false on failure.

## wait() [2/2]

static bool process::wait | ( | pid_t | pid,
|  | int32_t * | exitstatus
| ) |  |

static

This methods causes the process to wait until child process "pid" exits. If "exitstatus" is non-null then it is populated with the exit status of the child process. Returns true on success and false on failure.

## waitForChildren()

static void process::waitForChildren | ( |  | ) |

static

This method causes the process to wait on child processes which have exited, preventing so-called "zombie" processes from occurring.