Linux下C/C++查找某一进程

一、前言：要在程序中启动某一程序，如果程序已经存在了，就不再启动。查找了N篇文档，有所收获，总结一下。

二、实现

大体分两种：

1、exec或popen执行ps的命令行，然后运用某几个字符串匹配函数。

#include <stdio.h>#include <unistd.h>#include <string.h>#include <signal.h>int main(){    FILE *pstr; char cmd[128],buff[512],*p;    pid_t pID;    int pidnum;    char *name= "ping ";//要查找的进程名    int ret=3;    memset(cmd,0,sizeof(cmd));    sprintf(cmd, "ps -ef|grep %s ",name);    pstr=popen(cmd, "r");//    　　     if(pstr==NULL)    { return 1; }    memset(buff,0,sizeof(buff));    fgets(buff,512,pstr);    p=strtok(buff, " ");    p=strtok(NULL, " "); //这句是否去掉，取决于当前系统中ps后，进程ID号是否是第一个字段 pclose(pstr);    if(p==NULL)    { return 1; }    if(strlen(p)==0)    { return 1; }    if((pidnum=atoi(p))==0)    { return 1; }    printf("pidnum: %dn",pidnum);    pID=(pid_t)pidnum;    ret=kill(pID,0);//这里不是要杀死进程，而是验证一下进程是否真的存在，返回0表示真的存在    printf("ret= %d n",ret);    if(0==ret)        printf("process: %s exist!n",name);    else printf("process: %s not exist!n",name);    return 0;}

问题：这里是通过那个命令返回的信息是不是空来判断有没有这个进程的。还有一些实现是通过strcmp或者strstr来实现的。但是有个明显的问题就是，如果没有ping进程，而有个ping1之类的名字中带ping的进程，grep就废了。（貌似可以通过正则表达式实现，没实验过。）


2、读取/proc文件

找到个代码如下：

读取/proc文件查找进程

#ifndef __cplusplus//识别C/C++的宏，望文生意    #define _GNU_SOURCE#endif#include <unistd.h>#include <dirent.h>#include <sys/types.h> // for opendir(), readdir(), closedir()#include <sys/stat.h> // for stat()#ifdef __cplusplus    #include <iostream>    #include <cstdlib>    #include <cstring>    #include <cstdarg>#else    #include <stdio.h>    #include <stdlib.h>    #include <string.h>    #include <stdarg.h>#endif#define PROC_DIRECTORY "/proc/"#define CASE_SENSITIVE    1#define CASE_INSENSITIVE  0#define EXACT_MATCH       1#define INEXACT_MATCH     0//是不是数字int IsNumeric(const char* ccharptr_CharacterList){    for ( ; *ccharptr_CharacterList; ccharptr_CharacterList++)        if (*ccharptr_CharacterList < '0' || *ccharptr_CharacterList > '9')            return 0; // false    return 1; // true}//intCaseSensitive=0大小写不敏感int strcmp_Wrapper(const char *s1, const char *s2, int intCaseSensitive){    if (intCaseSensitive)        return !strcmp(s1, s2);    else        return !strcasecmp(s1, s2);}//intCaseSensitive=0大小写不敏感int strstr_Wrapper(const char* haystack, const char* needle, int intCaseSensitive){    if (intCaseSensitive)        return (int) strstr(haystack, needle);    else        return (int) strcasestr(haystack, needle);}#ifdef __cpluspluspid_t GetPIDbyName(const char* cchrptr_ProcessName, int intCaseSensitiveness, int intExactMatch)#elsepid_t GetPIDbyName_implements(const char* cchrptr_ProcessName, int intCaseSensitiveness, int intExactMatch)#endif{    char chrarry_CommandLinePath[100]  ;    char chrarry_NameOfProcess[300]  ;    char* chrptr_StringToCompare = NULL ;    pid_t pid_ProcessIdentifier = (pid_t) -1 ;    struct dirent* de_DirEntity = NULL ;    DIR* dir_proc = NULL ;    int (*CompareFunction) (const char*, const char*, int) ;    if (intExactMatch)        CompareFunction = &strcmp_Wrapper;    else        CompareFunction = &strstr_Wrapper;    dir_proc = opendir(PROC_DIRECTORY) ;    if (dir_proc == NULL)    {        perror("Couldn't open the " PROC_DIRECTORY " directory") ;        return (pid_t) -2 ;    }    // Loop while not NULL    while ( (de_DirEntity = readdir(dir_proc)) )    {        if (de_DirEntity->d_type == DT_DIR)        {            if (IsNumeric(de_DirEntity->d_name))            {                strcpy(chrarry_CommandLinePath, PROC_DIRECTORY) ;                strcat(chrarry_CommandLinePath, de_DirEntity->d_name) ;                strcat(chrarry_CommandLinePath, "/cmdline") ;                FILE* fd_CmdLineFile = fopen (chrarry_CommandLinePath, "rt") ;  //open the file for reading text                if (fd_CmdLineFile)                {                    fscanf(fd_CmdLineFile, "%s", chrarry_NameOfProcess) ; //read from /proc/<NR>/cmdline                    fclose(fd_CmdLineFile);  //close the file prior to exiting the routine                    if (strrchr(chrarry_NameOfProcess, '/'))                        chrptr_StringToCompare = strrchr(chrarry_NameOfProcess, '/') +1 ;                    else                        chrptr_StringToCompare = chrarry_NameOfProcess ;                    //printf("Process name: %sn", chrarry_NameOfProcess);                    //这个是全路径，比如/bin/ls                    //printf("Pure Process name: %sn", chrptr_StringToCompare );                    //这个是纯进程名，比如ls                    //这里可以比较全路径名，设置为chrarry_NameOfProcess即可                    if ( CompareFunction(chrptr_StringToCompare, cchrptr_ProcessName, intCaseSensitiveness) )                    {                        pid_ProcessIdentifier = (pid_t) atoi(de_DirEntity->d_name) ;                        closedir(dir_proc) ;                        return pid_ProcessIdentifier ;                    }                }            }        }    }    closedir(dir_proc) ;    return pid_ProcessIdentifier ;}#ifdef __cplusplus    pid_t GetPIDbyName(const char* cchrptr_ProcessName)    {        return GetPIDbyName(cchrptr_ProcessName, CASE_INSENSITIVE, EXACT_MATCH) ;    }#else    // C cannot overload functions - fixed    /*这里是原文的实现，但貌似需要某些牛X的设置，因不需要，删之    pid_t GetPIDbyName_Wrapper(const char* cchrptr_ProcessName, ... )    {        int intTempArgument ;        int intInputArguments[2] ;        // intInputArguments[0] = 0 ;        // intInputArguments[1] = 0 ;        memset(intInputArguments, 0, sizeof(intInputArguments) ) ;        int intInputIndex ;        va_list argptr;        va_start( argptr, cchrptr_ProcessName );            for (intInputIndex = 0;  (intTempArgument = va_arg( argptr, int )) != 15; ++intInputIndex)            {                intInputArguments[intInputIndex] = intTempArgument ;            }        va_end( argptr );        return GetPIDbyName_implements(cchrptr_ProcessName, intInputArguments[0], intInputArguments[1]);    }    #define GetPIDbyName(ProcessName,...) GetPIDbyName_Wrapper(ProcessName, ##__VA_ARGS__, (int) 15)    */    //简单实现    pid_t GetPIDbyName_Wrapper(const char* cchrptr_ProcessName)    {            return GetPIDbyName_implements(cchrptr_ProcessName, 0,0);//大小写不敏感    }#endifint main(){    pid_t pid = GetPIDbyName_Wrapper("bash") ; // If -1 = not found, if -2 = proc fs access error    printf("PID %dn", pid);    return EXIT_SUCCESS ;}

通过比较全路径，能一定程度上避免第1种方法的问题。

以下是整理后的C语言实现：

#include <unistd.h>#include <dirent.h>#include <sys/types.h> // for opendir(), readdir(), closedir()#include <sys/stat.h> // for stat()#include <stdio.h>#include <stdlib.h>#include <string.h>#include <stdarg.h>#define PROC_DIRECTORY "/proc/"#define CASE_SENSITIVE    1#define CASE_INSENSITIVE  0#define EXACT_MATCH       1#define INEXACT_MATCH     0//是不是数字int IsNumeric(const char* ccharptr_CharacterList){    for ( ; *ccharptr_CharacterList; ccharptr_CharacterList++)        if (*ccharptr_CharacterList < '0' || *ccharptr_CharacterList > '9')            return 0; // false    return 1; // true}//intCaseSensitive=0大小写不敏感int strcmp_Wrapper(const char *s1, const char *s2, int intCaseSensitive){    if (intCaseSensitive)        return !strcmp(s1, s2);    else        return !strcasecmp(s1, s2);}//intCaseSensitive=0大小写不敏感int strstr_Wrapper(const char* haystack, const char* needle, int intCaseSensitive){    if (intCaseSensitive)        return (int) strstr(haystack, needle);    else        return (int) strcasestr(haystack, needle);}pid_t GetPIDbyName_implements(const char* cchrptr_ProcessName, int intCaseSensitiveness, int intExactMatch){    char chrarry_CommandLinePath[100]  ;    char chrarry_NameOfProcess[300]  ;    char* chrptr_StringToCompare = NULL ;    pid_t pid_ProcessIdentifier = (pid_t) -1 ;    struct dirent* de_DirEntity = NULL ;    DIR* dir_proc = NULL ;    int (*CompareFunction) (const char*, const char*, int) ;    if (intExactMatch)        CompareFunction = &strcmp_Wrapper;    else        CompareFunction = &strstr_Wrapper;    dir_proc = opendir(PROC_DIRECTORY) ;    if (dir_proc == NULL)    {        perror("Couldn't open the " PROC_DIRECTORY " directory") ;        return (pid_t) -2 ;    }    // Loop while not NULL    while ( (de_DirEntity = readdir(dir_proc)) )    {        if (de_DirEntity->d_type == DT_DIR)        {            if (IsNumeric(de_DirEntity->d_name))            {                strcpy(chrarry_CommandLinePath, PROC_DIRECTORY) ;                strcat(chrarry_CommandLinePath, de_DirEntity->d_name) ;                strcat(chrarry_CommandLinePath, "/cmdline") ;                FILE* fd_CmdLineFile = fopen (chrarry_CommandLinePath, "rt") ;  //open the file for reading text                if (fd_CmdLineFile)                {                    fscanf(fd_CmdLineFile, "%s", chrarry_NameOfProcess) ; //read from /proc/<NR>/cmdline                    fclose(fd_CmdLineFile);  //close the file prior to exiting the routine                    if (strrchr(chrarry_NameOfProcess, '/'))                        chrptr_StringToCompare = strrchr(chrarry_NameOfProcess, '/') +1 ;                    else                        chrptr_StringToCompare = chrarry_NameOfProcess ;                    //printf("Process name: %sn", chrarry_NameOfProcess);                    //这个是全路径，比如/bin/ls                    //printf("Pure Process name: %sn", chrptr_StringToCompare );                    //这个是纯进程名，比如ls                    //这里可以比较全路径名，设置为chrarry_NameOfProcess即可                    if ( CompareFunction(chrptr_StringToCompare, cchrptr_ProcessName, intCaseSensitiveness) )                    {                        pid_ProcessIdentifier = (pid_t) atoi(de_DirEntity->d_name) ;                        closedir(dir_proc) ;                        return pid_ProcessIdentifier ;                    }                }            }        }    }    closedir(dir_proc) ;    return pid_ProcessIdentifier ;}    //简单实现    pid_t GetPIDbyName_Wrapper(const char* cchrptr_ProcessName)    {            return GetPIDbyName_implements(cchrptr_ProcessName, 0,0);//大小写不敏感    }int main(){    pid_t pid = GetPIDbyName_Wrapper("bash") ; // If -1 = not found, if -2 = proc fs access error    printf("PID %dn", pid);    return EXIT_SUCCESS ;}

通过比较全路径，一定程度上避免了1的问题。

原文链接: https://www.cnblogs.com/rusty/archive/2011/04/14/2016387.html

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