Linux下的C程序如何调用系统命令，并获取系统的输出信息到C程序中

#include <stdio.h>
#include <string.h>
#include <errno.h>

int main(int argc,char*argv[])
{
FILE *fstream=NULL;
char buff[1024];
memset(buff,0,sizeof(buff));
if(NULL==(fstream=popen("uname -a","r")))
{
fprintf(stderr,"execute command failed: %s",strerror(errno));
return -1;
}

if(NULL!=fgets(buff, sizeof(buff), fstream))
{
printf("=>%s",buff);
}
else
{
pclose(fstream);
return -1;
}
pclose(fstream);
return 0;
}

merlin@tfAnalysis:~/t/popen$ ./a.out
=>Linux tfAnalysis 3.13.0-35-generic #62-Ubuntu SMP Fri Aug 15 01:58:01 UTC 2014 i686 i686 i686 GNU/Linux
merlin@tfAnalysis:~/t/popen$