CentOS7环境下使用C语言统计指定端口流量

之前我在这篇文章里介绍了使用脚本方便地检测特定端口流量的方法。但是实际使用时发现脚本太过臃肿，执行效率不高，遂萌生出将其写为C程序的想法。下面提供我自己写的代码，以供参考。

注：本程序在

CentOS7x64

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

int daemon(int nochdir, int noclose);
int main(int argc, char *argv[], char *envp[])
{
daemon(1, 1);
//load parameters
char s_outputdir[100];
char s_result[20];
char s_command[strlen("iftop -nNtP -s 60 2>/dev/null | grep 65536 | cut -d b -f4 | sed 's/ //g' | grep B | sed -e '/Cumulative/d'") + 1];
double d_sum = 0;
sprintf(s_command, "ps aux | grep %s | sed -e '/grep/d' | cut -d ' ' -f1", argv[0]);
//printf("\n%s\n",s_command);
FILE *fp = NULL;
fp = popen(s_command, "r");
fgets(s_outputdir, sizeof(s_outputdir) - 1, fp);
memset(s_outputdir, 0, sizeof(s_outputdir));
fgets(s_outputdir, sizeof(s_outputdir) - 1, fp);
fclose(fp);
if(s_outputdir[0])
{
printf("\nprocess already exists!");
return 1;
}
//printf("%d", argc);	//when you enter 2 paras, it should be 3 now.
if(argc != 4 && argc != 2)
{
printf("\nwrong parameter numbers!\n");
return 1;
}
//printf("%s\n", argv[1]);
if(!strcmp(argv[1], "-h") || !strcmp(argv[1], "--help"))
{
printf("\nUsage:[command dir] <second> <port number> <file name>\n");
return 0;
}
if(atoi(argv[1]) > 60 || atoi(argv[1]) <= 0)
{
printf("\nsecond larger than 1 min or less than 1 sec.!\n");
return 1;
}
if(atoi(argv[2]) > 65536 || atoi(argv[2]) <= 0)
{
printf("\nport number should be smaller than 65536 and larger than 0!\n");
return 1;
}
strcpy(s_outputdir, argv[3]);
//printf("%s %s\n", s_second, s_portnumber);
//prepare for the shell cmd.
sprintf(s_command,"iftop -nNtP -s %s 2>/dev/null | grep %s | cut -d b -f4 | sed 's/ //g' | grep B | sed -e '/Cumulative/d'", argv[1], argv[2]);
//printf("%s\n", s_command);
//do iftop
while(1){       //make a daemon.
fp = NULL;
fp = popen(s_command, "r");
if(!fp)
{
printf("\ndoing shell error!\n");
return 1;
}
memset(s_result, 0, sizeof(s_result));
d_sum = 0;
//load result and make a sum.
while(fgets(s_result, sizeof(s_result) - 1, fp))
{
//printf("%s %d\n", s_result, strlen(s_result));	//when result is 1.76MB, strlen is 7.
if(s_result[0] == 'B' || s_result[0]=='K' || s_result[0] == 'M')continue;
else if(s_result[strlen(s_result) - 3] == 'M'){d_sum += atof(s_result);continue;}
else if(s_result[strlen(s_result) - 3] == 'K'){d_sum += atof(s_result)/1000;continue;}
else {d_sum += atof(s_result)/1000000;continue;}
}
pclose(fp);
//printf("\nbefore open the file:%f\n",d_sum);
//output sum to a file.
fp = NULL;
fp = fopen(s_outputdir, "r");
//printf("opened the file with ro.\n");
memset(s_result, 0, sizeof(s_result));
if(!fp)printf("\nno file exist! trying to create one.\n");
else
{
fgets(s_result, sizeof(s_result) - 1, fp);	//we borrow s_result to load the old sum.
fclose(fp);
//printf("closed the file in ro.\n");
}
fp = NULL;
//printf("opened the file in wo\n");
fp = fopen(s_outputdir, "w");
//printf("\nold:%fMB\n", d_sum);
d_sum+=atof(s_result);
//printf("\nnew:%fMB\n", d_sum);
fprintf(fp,"%fMB\n", d_sum);
fclose(fp);
//printf("closed the file.\n");
}
return 0;
}