linux程序设计113页 怎么我跑不通?
先贴下代码<code>
#include<unistd.h>
#include<stdio.h>
#include<sys/mman.h>
#include<fcntl.h>
#include<stdlib.h>
typedef struct {
int integer;
char string;
} RECORD;
#define NRECORDS (100)
int main()
{
RECORD record, *mapped;
int i, f;
FILE *fp;
fp=fopen("records.dat","w+");
for(i=0;i<NRECORDS;i++)
{
record.integer = i;
sprintf(record.string,"RECORD-%d",i);
fwrite(&record,sizeof(record),1,fp);
}
fclose(fp);
printf("#############1#############\n");
fp = fopen("records.dat","r+");
fseek(fp,43*sizeof(record),SEEK_SET);
fread(&record,sizeof(record),1,fp);
record.integer = 143;
sprintf(record.string,"RECORD-%d",record.integer);
fseek(fp,43*sizeof(record),SEEK_SET);
fwrite(&record,sizeof(record),1,fp);
fclose(fp);
printf("###############2##############\n");
f = open("record.dat",O_RDWR);
mapped = (RECORD *)mmap(0,NRECORDS*sizeof(record),PROT_READ|PROT_WRITE,MAP_SHARED,f,0);
mapped.integer = 243;
sprintf(mapped.string,"RECORD-%d",mapped.integer);
msync((void *)mapped,NRECORDS*sizeof(record), MS_ASYNC);
munmap((void *)mapped, NRECORDS*sizeof(record));
close(f);
printf("##################3#############\n");
exit(0);
}
</code>
经过我调试发现mapped.integer = 243这行出现段错误。 不知道为什么。。。。 1、f = open("record.dat",O_RDWR); 检查文件是否有被打开
2、mapped = (RECORD *)mmap(0,NRECORDS*sizeof(record),PROT_READ|PROT_WRITE,MAP_SHARED,f,0);检查mmap是否成功
没有成功当然段错误 额真的是文件打开失败!这是为什么?。。。。回复 2# lxyscls_cu
额 发现问题了文件名字错了 少了个s太马虎了。。。。看来必须验证函数是否成功啊,不然后果很严重。。。
非常感谢哈 !!!!!!!!!!!!!!!!!!!1回复 2# lxyscls_cu
要谨慎的编码, 习惯了就好了, 不麻烦.
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