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Important: This sample code may not represent best practices for current development. The project may use deprecated symbols and illustrate technologies and techniques that are no longer recommended.
GetPID.c
/* |
File: GetPID.c |
Description: This file provides a simple API to do process PID lookup based on process name. |
Author: Chad Jones |
Copyright: © Copyright 2003 Apple Computer, Inc. All rights reserved. |
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*/ |
#include "GetPID.h" |
#include <errno.h> |
#include <string.h> |
#include <sys/sysctl.h> |
/***************************************************** |
* GetAllPIDsForProcessName |
***************************************************** |
* Purpose: This functions purpose is to lookup a BSD |
* process PID given the BSD process name. This function may |
* potentially return multiple PIDs for a given BSD process name |
* since several processes can have the same BSD process name. |
* |
* Parameters: |
* ProcessName A constant C-string. On calling |
* GetAllPIDsForProcessName this variable holds the BSD process name |
* used to do the process lookup. Note that the process name you need |
* to pass is the name of the BSD executable process. If trying |
* to find the PID of an regular OSX application you will need to pass the |
* name of the actual BSD executable inside an application bundle (rather |
* than the bundle name itself). In any case as a user you can find the |
* BSD process name of any process (including OSX applications) by |
* typing the command "ps -axcocommand,pid" in terminal. |
* |
* ArrayOfReturnedPIDs A pointer to a pre-allocated array of pid_t. |
* On calling GetAllPIDsForProcessName this variable must be a pointer to a |
* pre-allocated array of pid_t whos length (in number of pid_t entries) is defined |
* in ArrayOfPIDsLength. On successful return from GetAllPIDsForProcessName |
* this array will hold the PIDs of all processes which have a matching process |
* name to that specified in the ProcessName input variable. The number of actual |
* PIDs entered in the array starting at index zero will be the value returned |
* in NumberOfMatchesFound. On failed return if the error is a buffer overflow |
* error then the buffer will be filled to the max with PIDs which matched. |
* Otherwise on failed return the state of the array will be undefined. Note |
* the returned PID array is not sorted and is listed in order of process encountered. |
* |
* NumberOfPossiblePIDsInArray A unsigned integer. On calling |
* GetAllPIDsForProcessName this variable will hold the number of |
* pre-allocated PID entries which are in the ArrayOfReturnedPIDs for this functions |
* use. Note this value must have a value greater than zero. |
* |
* NumberOfMatchesFound An unsigned integer. On calling GetAllPIDsForProcessName |
* this variable will point to a pre-allocated unsigned integer. On return from |
* GetAllPIDsForProcessName this variable will contain the number of PIDs contained in the |
* ArrayOfReturnedPIDs. On failed return the value of the variable will be undefined. |
* |
* SysctlError A pointer to a pre-allocated integer. On failed return, this |
* variable represents the error returned from the sysctl command. On function |
* success this variable will have a value specified by the sysctl based on the |
* error that occurred. On success the variable will have the value zero. |
* Note this variable can also be NULL in which case the variable is ignored. |
* |
* *Function Result* A integer return value. |
* See result codes listed below. |
* Result Codes: |
* 0 Success. A set of process PIDs were found and are located in |
* ArrayOfReturnedPIDs array. |
* -1 Could not find a process with a matching process name |
* (i.e. process not found). |
* -2 Invalid arguments passed. |
* -3 Unable to get the size of sysctl buffer required |
* (consult SysctlError return value for more information) |
* -4 Unable to allocate memory to store BSD process information |
* (consult SysctlError return value for more information) |
* -5 The array passed to hold the returned PIDs is not large enough |
* to hold all PIDs of process with matching names. |
* |
*****************************************************/ |
int GetAllPIDsForProcessName(const char* ProcessName, |
pid_t ArrayOfReturnedPIDs[], |
const unsigned int NumberOfPossiblePIDsInArray, |
unsigned int* NumberOfMatchesFound, |
int* SysctlError) |
{ |
// --- Defining local variables for this function and initializing all to zero --- // |
int mib[6] = {0,0,0,0,0,0}; //used for sysctl call. |
int SuccessfullyGotProcessInformation; |
size_t sizeOfBufferRequired = 0; //set to zero to start with. |
int error = 0; |
long NumberOfRunningProcesses = 0; |
unsigned int Counter = 0; |
struct kinfo_proc* BSDProcessInformationStructure = NULL; |
pid_t CurrentExaminedProcessPID = 0; |
char* CurrentExaminedProcessName = NULL; |
// --- Checking input arguments for validity --- // |
if (ProcessName == NULL) //need valid process name |
{ |
return(kInvalidArgumentsError); |
} |
if (ArrayOfReturnedPIDs == NULL) //need an actual array |
{ |
return(kInvalidArgumentsError); |
} |
if (NumberOfPossiblePIDsInArray <= 0) |
{ |
//length of the array must be larger than zero. |
return(kInvalidArgumentsError); |
} |
if (NumberOfMatchesFound == NULL) //need an integer for return. |
{ |
return(kInvalidArgumentsError); |
} |
//--- Setting return values to known values --- // |
//initalizing PID array so all values are zero |
memset(ArrayOfReturnedPIDs, 0, NumberOfPossiblePIDsInArray * sizeof(pid_t)); |
*NumberOfMatchesFound = 0; //no matches found yet |
if (SysctlError != NULL) //only set sysctlError if it is present |
{ |
*SysctlError = 0; |
} |
//--- Getting list of process information for all processes --- // |
/* Setting up the mib (Management Information Base) which is an array of integers where each |
* integer specifies how the data will be gathered. Here we are setting the MIB |
* block to lookup the information on all the BSD processes on the system. Also note that |
* every regular application has a recognized BSD process accociated with it. We pass |
* CTL_KERN, KERN_PROC, KERN_PROC_ALL to sysctl as the MIB to get back a BSD structure with |
* all BSD process information for all processes in it (including BSD process names) |
*/ |
mib[0] = CTL_KERN; |
mib[1] = KERN_PROC; |
mib[2] = KERN_PROC_ALL; |
/* Here we have a loop set up where we keep calling sysctl until we finally get an unrecoverable error |
* (and we return) or we finally get a succesful result. Note with how dynamic the process list can |
* be you can expect to have a failure here and there since the process list can change between |
* getting the size of buffer required and the actually filling that buffer. |
*/ |
SuccessfullyGotProcessInformation = FALSE; |
while (SuccessfullyGotProcessInformation == FALSE) |
{ |
/* Now that we have the MIB for looking up process information we will pass it to sysctl to get the |
* information we want on BSD processes. However, before we do this we must know the size of the buffer to |
* allocate to accomidate the return value. We can get the size of the data to allocate also using the |
* sysctl command. In this case we call sysctl with the proper arguments but specify no return buffer |
* specified (null buffer). This is a special case which causes sysctl to return the size of buffer required. |
* |
* First Argument: The MIB which is really just an array of integers. Each integer is a constant |
* representing what information to gather from the system. Check out the man page to know what |
* constants sysctl will work with. Here of course we pass our MIB block which was passed to us. |
* Second Argument: The number of constants in the MIB (array of integers). In this case there are three. |
* Third Argument: The output buffer where the return value from sysctl will be stored. In this case |
* we don't want anything return yet since we don't yet know the size of buffer needed. Thus we will |
* pass null for the buffer to begin with. |
* Forth Argument: The size of the output buffer required. Since the buffer itself is null we can just |
* get the buffer size needed back from this call. |
* Fifth Argument: The new value we want the system data to have. Here we don't want to set any system |
* information we only want to gather it. Thus, we pass null as the buffer so sysctl knows that |
* we have no desire to set the value. |
* Sixth Argument: The length of the buffer containing new information (argument five). In this case |
* argument five was null since we didn't want to set the system value. Thus, the size of the buffer |
* is zero or NULL. |
* Return Value: a return value indicating success or failure. Actually, sysctl will either return |
* zero on no error and -1 on error. The errno UNIX variable will be set on error. |
*/ |
error = sysctl(mib, 3, NULL, &sizeOfBufferRequired, NULL, NULL); |
/* If an error occurred then return the accociated error. The error itself actually is stored in the UNIX |
* errno variable. We can access the errno value using the errno global variable. We will return the |
* errno value as the sysctlError return value from this function. |
*/ |
if (error != 0) |
{ |
if (SysctlError != NULL) |
{ |
*SysctlError = errno; //we only set this variable if the pre-allocated variable is given |
} |
return(kErrorGettingSizeOfBufferRequired); |
} |
/* Now we successful obtained the size of the buffer required for the sysctl call. This is stored in the |
* SizeOfBufferRequired variable. We will malloc a buffer of that size to hold the sysctl result. |
*/ |
BSDProcessInformationStructure = (struct kinfo_proc*) malloc(sizeOfBufferRequired); |
if (BSDProcessInformationStructure == NULL) |
{ |
if (SysctlError != NULL) |
{ |
*SysctlError = ENOMEM; //we only set this variable if the pre-allocated variable is given |
} |
return(kUnableToAllocateMemoryForBuffer); //unrecoverable error (no memory available) so give up |
} |
/* Now we have the buffer of the correct size to hold the result we can now call sysctl |
* and get the process information. |
* |
* First Argument: The MIB for gathering information on running BSD processes. The MIB is really |
* just an array of integers. Each integer is a constant representing what information to |
* gather from the system. Check out the man page to know what constants sysctl will work with. |
* Second Argument: The number of constants in the MIB (array of integers). In this case there are three. |
* Third Argument: The output buffer where the return value from sysctl will be stored. This is the buffer |
* which we allocated specifically for this purpose. |
* Forth Argument: The size of the output buffer (argument three). In this case its the size of the |
* buffer we already allocated. |
* Fifth Argument: The buffer containing the value to set the system value to. In this case we don't |
* want to set any system information we only want to gather it. Thus, we pass null as the buffer |
* so sysctl knows that we have no desire to set the value. |
* Sixth Argument: The length of the buffer containing new information (argument five). In this case |
* argument five was null since we didn't want to set the system value. Thus, the size of the buffer |
* is zero or NULL. |
* Return Value: a return value indicating success or failure. Actually, sysctl will either return |
* zero on no error and -1 on error. The errno UNIX variable will be set on error. |
*/ |
error = sysctl(mib, 3, BSDProcessInformationStructure, &sizeOfBufferRequired, NULL, NULL); |
//Here we successfully got the process information. Thus set the variable to end this sysctl calling loop |
if (error == 0) |
{ |
SuccessfullyGotProcessInformation = TRUE; |
} |
else |
{ |
/* failed getting process information we will try again next time around the loop. Note this is caused |
* by the fact the process list changed between getting the size of the buffer and actually filling |
* the buffer (something which will happen from time to time since the process list is dynamic). |
* Anyways, the attempted sysctl call failed. We will now begin again by freeing up the allocated |
* buffer and starting again at the beginning of the loop. |
*/ |
free(BSDProcessInformationStructure); |
} |
}//end while loop |
// --- Going through process list looking for processes with matching names --- // |
/* Now that we have the BSD structure describing the running processes we will parse it for the desired |
* process name. First we will the number of running processes. We can determine |
* the number of processes running because there is a kinfo_proc structure for each process. |
*/ |
NumberOfRunningProcesses = sizeOfBufferRequired / sizeof(struct kinfo_proc); |
/* Now we will go through each process description checking to see if the process name matches that |
* passed to us. The BSDProcessInformationStructure has an array of kinfo_procs. Each kinfo_proc has |
* an extern_proc accociated with it in the kp_proc attribute. Each extern_proc (kp_proc) has the process name |
* of the process accociated with it in the p_comm attribute and the PID of that process in the p_pid attibute. |
* We test the process name by compairing the process name passed to us with the value in the p_comm value. |
* Note we limit the compairison to MAXCOMLEN which is the maximum length of a BSD process name which is used |
* by the system. |
*/ |
for (Counter = 0 ; Counter < NumberOfRunningProcesses ; Counter++) |
{ |
//Getting PID of process we are examining |
CurrentExaminedProcessPID = BSDProcessInformationStructure[Counter].kp_proc.p_pid; |
//Getting name of process we are examining |
CurrentExaminedProcessName = BSDProcessInformationStructure[Counter].kp_proc.p_comm; |
if ((CurrentExaminedProcessPID > 0) //Valid PID |
&& ((strncmp(CurrentExaminedProcessName, ProcessName, MAXCOMLEN) == 0))) //name matches |
{ |
// --- Got a match add it to the array if possible --- // |
if ((*NumberOfMatchesFound + 1) > NumberOfPossiblePIDsInArray) |
{ |
//if we overran the array buffer passed we release the allocated buffer give an error. |
free(BSDProcessInformationStructure); |
return(kPIDBufferOverrunError); |
} |
//adding the value to the array. |
ArrayOfReturnedPIDs[*NumberOfMatchesFound] = CurrentExaminedProcessPID; |
//incrementing our number of matches found. |
*NumberOfMatchesFound = *NumberOfMatchesFound + 1; |
} |
}//end looking through process list |
free(BSDProcessInformationStructure); //done with allocated buffer so release. |
if (*NumberOfMatchesFound == 0) |
{ |
//didn't find any matches return error. |
return(kCouldNotFindRequestedProcess); |
} |
else |
{ |
//found matches return success. |
return(kSuccess); |
} |
} |
/***************************************************** |
* GetPIDForProcessName |
***************************************************** |
* Purpose: A convience call for GetAllPIDsForProcessName(). |
* This function looks up a process PID given a BSD process |
* name. |
* |
* Parameters: |
* ProcessName A constant C-string. On calling |
* GetPIDForProcessName this variable holds the BSD process name |
* used to do the process lookup. Note that the process name you need |
* to pass is the name of the BSD executable process. If trying |
* to find the PID of an regular OSX application you will need to pass the |
* name of the actual BSD executable inside an application bundle (rather |
* than the bundle name itself). In any case as a user you can find the |
* BSD process name of any process (including OSX applications) by |
* typing the command "ps -axcocommand,pid" in terminal. |
* |
* *Function Result* A integer return value. |
* See result codes listed below. |
* Result Codes: |
* >0 Success. The value returned is the PID of the |
* matching process. |
* -1 Error getting PID for requested process. This error can |
* be caused by several things. One is if no such process exists. |
* Another is if more than one process has the given name. The |
* thing to do here is to call GetAllPIDsForProcessName() |
* for complete error code or to get PIDs if there are multiple |
* processes with that name. |
*****************************************************/ |
int GetPIDForProcessName(const char* ProcessName) |
{ |
pid_t PIDArray[1] = {0}; |
int Error = 0; |
int NumberOfMatches = 0; |
/* Here we are calling the function GetAllPIDsForProcessName which wil give us the PIDs |
* of the process name we pass. Of course here we are hoping for a single PID return. |
* First Argument: The BSD process name of the process we want to lookup. In this case the |
* the process name passed to us. |
* Second Argument: A preallocated array of pid_t. This is where the PIDs of matching processes |
* will be placed on return. We pass the array we just allocated which is length one. |
* Third Argument: The number of pid_t entries located in the array of pid_t (argument 2). In this |
* case our array has one pid_t entry so pass one. |
* Forth Argument: On return this will hold the number of PIDs placed into the |
* pid_t array (array passed in argument 2). |
* Fifth Argument: Passing NULL to ignore this argument. |
* Return Value: An error indicating success (zero result) or failure (non-zero). |
* |
*/ |
Error = GetAllPIDsForProcessName(ProcessName, PIDArray, 1, &NumberOfMatches, NULL); |
if ((Error == 0) && (NumberOfMatches == 1))//success! |
{ |
return((int) PIDArray[0]); //return the one PID we found. |
} |
else |
{ |
return(-1); |
} |
} |
Copyright © 2003 Apple Computer, Inc. All Rights Reserved. Terms of Use | Privacy Policy | Updated: 2003-02-13