有時候我們除錯系統時，需要在執行過程中檢視某個任務的狀態，如一些任務的cpu親和性。但是我們我們只知道要監控的任務的名字，任務的pid是動態分配的。

     下面這個程式就是在c中通過popen()執行一段shell程式以通過任務名字找到對應的PID，然後再根據PID檢視任務的cpu親和性：

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#include <string.h>  
#include <sys/types.h>  
#define __USE_GNU
#include <sched.h>
#include<sys/sysinfo.h>
#include <unistd.h>
#define PS_COMMAND "ps aux | grep %s | grep -v grep| awk \'{print $1}\'"
int getaffinity_by_name(char *name)  
{  
	FILE *fp;  
	char buf[128]={0}, cmd[64];  
	pid_t pid;
 	cpu_set_t cpuset;
	int i = 0, num = sysconf(_SC_NPROCESSORS_CONF);
	unsigned long long cpumask = 0;

	sprintf(cmd, PS_COMMAND, name);
 	printf(" cmd=[%s]\n", cmd);
	if ((fp = popen(cmd, "r")) == NULL)  
		return -1;  

	if(!fgets(buf, sizeof(buf), fp))
		return -1;
	fclose(fp);
	pid = strtol(buf, 0, 10);

	if (pid != 0) {
		cpumask = getaffinity_by_tid(pid);
		printf(" %s's cpumask is 0x%llx\n", name, cpumask);
		return 0;	
   	 } else {
		printf(" strtol(%s) invalid\n", buf);
		return -1;
	}
}
int getaffinity_by_tid(pid_t pid)
{
	int i;
	cpu_set_t cpuset;
	unsigned long long cpumask = 0;
	int i = 0, num = sysconf(_SC_NPROCESSORS_CONF);

	if (pid != 0) {
		CPU_ZERO(&cpuset);
		sched_getaffinity(pid, sizeof(cpuset), &cpuset);
		for (i = 0; i < num; i++){
			if (CPU_ISSET(i, &cpuset))
				cpumask |= 1 << i;
		}
	 }
	 return cpumask;
}

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