c - 分段故障归档 sleep 功能

Question

大家好，我遇到了一个问题。我正在使用 sleep 功能。我有一个文件，5 秒后打开，读取所有数据并显示它。它运行了几次，给出了段错误，我不明白为什么会发生。我认为程序文件没有任何问题，否则它一定热运行了谢谢 请帮助我
这是代码

#include<stdio.h>
#include <sys/stat.h>
#include<time.h>
#include<string.h>
void retrive()
{
FILE *fs;
char ch;
const int size =26;
const int size1 =3;
const int size2 =6;
        char sourceip[size];char destip[size];char sourceport[size2];char destport[size2];
        char sessionstart[size];char sessionend[size];char payload[size2];char sessionnum[size2]; 
  while(-1)
{      
    fs = fopen ( "processpacketlib.txt","r" ) ;
        if ( fs == NULL )
        {
               puts ( "Cannot open source file" ) ;
               return 0;
        }
int j;
int cnt =0;
printf("no of entries %d" , (noofentries("processpacketlib.txt")+1)/3);

//while(cnt<(noofentries("processpacketlib.txt")/3))
for(j=0;j<10;j++)
///ch= fgetc(fs);
//while(ch!=EOF)
{
int i=0;
printf("j = %d" ,j);
ch= fgetc(fs);
sourceip[i]=ch;
i++;
while ( ch!='\t')
        {

ch = fgetc ( fs ) ;        
sourceip[i]=ch;
        i++;
         }
sourceip[--i]='\0';
 i=0;
//================================================

ch = fgetc ( fs ) ;
destip[i]=ch;
i++;
while ( ch!='\t' )
        {

        ch = fgetc ( fs ) ;
        destip[i]=ch;

i++;
         }

destip[--i]='\0';
i=0;
//=================================================

ch = fgetc ( fs ) ;
sourceport[i]=ch;
//printf("eh %c",eh[0])   ;
i++;
while (ch!='\t')
{
ch = fgetc ( fs ) ;
sourceport[i]=ch;
//printf("eh %c",eh[1])   ;
i++;
 }
sourceport[--i]='\0';
i=0;
//=================================================

ch = fgetc ( fs ) ;
destport[i]=ch;
//printf("np %c",np[0])   ;
i++;
while (ch!='\t')
{
ch = fgetc ( fs ) ;
destport[i]=ch;
//printf("np %c",np[1])   ;
i++;
 }
destport[--i]='\0';
i=0;
//===============================================

ch = fgetc ( fs ) ;
payload[i]=ch;
//printf("np %c",np[0])   ;
i++;
while (ch!='\t')
{
ch = fgetc ( fs ) ;
payload[i]=ch;
//printf("np %c",np[1])   ;
i++;
 }
payload[--i]='\0';
i=0;

//==================================================

//==================================================

ch = fgetc ( fs ) ;
sessionnum[i]=ch;
//printf("np %c",np[0])   ;
i++;
while (ch!='\t')
{
ch = fgetc ( fs ) ;
sessionnum[i]=ch;
//printf("np %c",np[1])   ;
i++;
 }
sessionnum[--i]='\0';
i=0;


//=================================================
ch = fgetc ( fs ) ;
sessionstart[i]=ch;
//printf("np %c",np[0])   ;
i++;
while (ch!='\n')
{
ch = fgetc ( fs ) ;
sessionstart[i]=ch;
//printf("np %c",np[1])   ;
i++;
 }
sessionstart[--i]='\0';
i=0;
//======================================================

ch = fgetc ( fs ) ;
sessionend[i]=ch;
//printf("np %c",np[0])   ;
i++;
while (ch!='\n')
{
ch = fgetc ( fs ) ;
sessionend[i]=ch;
//printf("np %c",np[1])   ;
i++;
 }
sessionend[--i]='\0';

ch = fgetc ( fs ) ;
//----------------------------------------------------*/
csvwrite(sourceip,destip,sourceport,destport,sessionstart,sessionend,payload,sessionnum);

printf("\nsip %s" , sourceip);
printf("\n dip %s" , destip);
printf("\nsource  %s",sourceport);
printf("\ndest %s",destport);
printf("\nt pay  %s",payload);
printf("\nt hdr %s",sessionnum);
printf("\nsession strat %s",sessionstart);
printf("\nsession end %s",sessionend);

printf("\n");

cnt++;
}// while ends
fclose(fs);
sleep(1);
}// outer infinite while ends

}
//==================================================================================

void csvwrite(char sourceip[],char destip[],char sourceport[],char destport[],char sessionstart[],char sessionend[],char payload[],char sessionnum[])
 {int retvalue;
int pos=0;
   char snum[5];char sstime[20];char payload1[10000] ;
struct tm tm;
time_t t;
char s[25]="Sat Feb 19 12:53:39 2011";
if (strptime(sessionstart, "%A %b %d %H:%M:%S %Y", &tm) != NULL)
tm.tm_isdst = -1;      
t = mktime(&tm);
//if (t != -1)
//printf("seconds since the Epoch: %ld\n", (long) t);
char filename[35];
sprintf(filename,"%s%s%s%s",sourceip,"_",destip,".csv");
printf("filename %s",filename);

   FILE *fe = fopen(filename,"a");

   struct stat st;
   stat(filename, &st);
   int fsize = st.st_size;
   printf("before file size %d\n\n\n" ,fsize);        
if(fsize==0)
 {
        char stringtime[15];
    fprintf(fe,"%s",sessionnum);
    fprintf(fe,"%s"," ");
        sprintf(stringtime,"%ld",(long)t);
    fprintf(fe,"%s",stringtime);
    fprintf(fe,"%s"," ");
    fprintf(fe,"%s",payload);
    fprintf(fe,"%s","\n");
        fclose(fe);
        struct stat st1;
        stat(filename, &st1);
        int fsize1 = st1.st_size; 
        printf("after file size %d\n\n\n" ,fsize1);
   }
//fclose(filenname);
else
 {
    int count =noofentries(filename);
    printf("count%d",count);
    int i=0;
    int k=0;
int len =0;

    FILE *f1 = fopen(filename,"r");
    //char snum[5];char sstime[20];char payload1[100000] ; int payloadentries=0;// change pasted below
while(k<count)
     {char snum[5];char sstime[20];char payload1[100000] ; int payloadentries=0;

          char ch;
      ch= fgetc(f1);
      pos++;
          len++;
          // printf("\nch = %c" ,ch);
          snum[i]=ch;
          i++;
        while (ch!=' ')
                {
                    ch = fgetc ( f1 ) ;
                pos++;
                len++;
                    snum[i]=ch;
                    //  printf("ch %c",ch)   ;
                    i++;
            }
                snum[--i]='\0';
                i=0;
//--------------------------------------------
                ch= fgetc(f1);
                pos++;
                len++;
                    // printf("\nch = %c" ,ch);
                    sstime[i]=ch;
                                i++;
              while (ch!=' ')
                     {
                    ch = fgetc ( f1 ) ;
                pos++;
                len++;
                    sstime[i]=ch;
                    //  printf("ch %c",ch)   ;
                                i++;
                    }
                    sstime[--i]='\0';
                    i=0;
//---------------------------------------------
                    ch= fgetc(f1);
                pos++;
                len++;
                    // printf("\nch = %c" ,ch);
                payload1[i]=ch;
                    i++;
         while (ch!='\n')
                   {
                    ch = fgetc ( f1) ;
                pos++;
                len++;
                    payload1[i]=ch;
                    //  printf("ch %c",ch)   ;
                    i++;
                if(ch==' ')
                      {
                     payloadentries++;
                                      }

                  }
                payload1[--i]='\0';
                i=0;
                printf("\nsnum %s" ,snum);

                printf("\nsstime %s" ,sstime);

                printf("\npayload %s" ,payload1);

//  retvalue=addpayload(sourceip,destip,sourceport,destport,t,payload,sessionnum,snum,sstime,payload1,payloadentries+1,pos,count,filename);
//printf("rettttttttttvalue %d" ,retvalue);
        if ((retvalue==-2)||(retvalue==-1))
        {
printf("\n\nBREAK\n\n ");
         break;
        }
           k++;

   }//while end
           fclose(f1);
 } //else end
}// function end
//====================================================================================

Answer 1

csvwrite() 中 if(fsize==0) 条件的 else 分支不 fclose(fe) 。任何一个进程可以同时打开的文件数量是有限制的；如果调用此函数的次数足够多，就会达到限制，并且下一个 fopen() 将返回 NULL (并且将设置 errno到 EMFILE - “打开的文件太多”)。

这可能是也可能不是问题，所以这里有一些更一般的建议:

1. 使用调试器。如果你不知道怎么做，你应该学习!例如:

   $ cat test.c
   #include <stdio.h>
   
   int main(void)
   {
       int a = 123, b, c;
       int *p = &a;
       int *q = NULL;
   
       b = *p;
       c = *q;
       printf("%d %d\n", b, c);
       return 0;
   }
   $ gcc -Wall -o test test.c
   $ ./test
   Segmentation fault
   $
   

   不是很有帮助。但使用 -g 编译并使用 gdb 运行:

   $ gcc -g -Wall -o test test.c$ gdb ./testGNU gdb 6.8-debianCopyright (C) 2008 Free Software Foundation, Inc.License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>This is free software: you are free to change and redistribute it.There is NO WARRANTY, to the extent permitted by law.  Type "show copying"and "show warranty" for details.This GDB was configured as "i486-linux-gnu"...(gdb) runStarting program: /tmp/test 

   ...它会显示失败的行:

   Program received signal SIGSEGV, Segmentation fault.0x080483d4 in main () at test.c:1010        c = *q;(gdb) quitThe program is running.  Exit anyway? (y or n) y$ 

2. 在启用警告的情况下进行编译(正如我上面使用 -Wall 标志所做的那样)。编译器能够发现很多愚蠢的事情，但你必须问它。

3. 尝试合理地缩进代码。可读的代码更容易调试。

4. 记住检查返回值。 fopen() 尤其可能因与您的程序无关的多种原因而失败。

5. 不要编写大量几乎相同的代码。如果您必须多次执行相同的工作，请考虑将其分解为一个单独的函数。