使用java和c语言在linux下通过进程名获取进程id

在linux下通过进程名获取进程id，一般使用ps命令，ps -A |grep openvpn。
其实linux的每个进程都会在/proc伪目录下存放相应信息。
先给出c程序
添加头文件
#include
#include
#define READ_BUF_SIZE    50
函数
pid_t* find_pid_by_name( char* pidName)
{
    DIR *dir;
    struct dirent *next;
    pid_t* pidList=NULL;
    int i=0;

    dir = opendir("/proc");


    while ((next = readdir(dir)) != NULL) {
        FILE *status;
        char filename[READ_BUF_SIZE];
        char buffer[READ_BUF_SIZE];
        char name[READ_BUF_SIZE];

        /* Must skip ".." since that is outside /proc */
        if (strcmp(next->d_name, "..") == 0)
            continue;

        /* If it isn't a number, we don't want it */
        if (!isdigit(*next->d_name))
            continue;

        sprintf(filename, "/proc/%s/status", next->d_name);
        if (! (status = fopen(filename, "r")) ) {
            continue;
        }
        if (fgets(buffer, READ_BUF_SIZE-1, status) == NULL) {
            fclose(status);
            continue;
        }
        fclose(status);

        /* Buffer should contain a string like "Name:   binary_name" */
        sscanf(buffer, "%*s %s", name);

        if (strcmp(name, pidName) == 0) {
            pidList=realloc( pidList, sizeof(pid_t) * (i+2));
            pidList[i++]=strtol(next->d_name, NULL, 0);
        }
    }


    return pidList;
}
调用方法
pid_t* pidList, *tmpList;
    
    pidList = find_pid_by_name("openvpn");
    if (!pidList || *pidList<=0) {
        
    }
    tmpList = pidList;
    for(; pidList && *pidList!=0; pidList++)
    {
        

    }
    free(tmpList);
java的原理类似，我引入apache的commons io，其实这个包可以不用
import org.apache.commons.io.FileUtils;
import org.apache.commons.io.IOUtils;
import org.apache.commons.io.LineIterator;
先写一个filter
public class PidFileFilter implements FileFilter
{


    public boolean accept(File file)
    {
        String fileName = file.getName();
        char digit = fileName.charAt(0);
        if(Character.isDigit(digit))
        {

         return true;
        }
        return false;
    }
}
不是数字开头的全不要
函数 返回一个list，里面存有所有的pid
public List getPid(String processname)
    {
        File rootFolder = new File("/proc");
        File[] files = rootFolder.listFiles(new PidFileFilter());
        List ls=new ArrayList();
        for (File f : files)
        {
            File file1 = new File("/proc/"+f.getName()+"/status");
            try {
                LineIterator it = FileUtils.lineIterator(file1, "UTF-8");
                try {
                    while (it.hasNext()) {
                        String line = it.nextLine();
                        String []name = line.split("\t") ;

                        if(name[0].equals("Name:") && name[1].equals(processname))
                        {
                            ls.add(f.getName());
                        }
                        break;
                    }
                } finally {
                    LineIterator.closeQuietly(it);
                }

            } catch (IOException e) {
                e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
            }
       }


        return ls;
    }
相比之下 ，觉得还是c语言逻辑清晰，代码容易理解。