I'm doing a read from a file, but the input seems to "overflow" into other variables.
I have these 2 variables:
char str[250]; //used to store input from stream
char *getmsg; //already points to some other string
The problem is, when I use fgets() to read the input
printf("1TOKEN:%s\n",getmsg);
fp=fopen("m.txt","r");
fp1=fopen("m1.txt","w");
if(fp!=NULL && fp1!=NULL)
printf("2TOKEN:%s\n",getmsg);
while(fgets(str,250,fp)!=NULL){
printf("3TOKEN:%s\n",getmsg);
printf("read:%s",str);
printf("4TOKEN:%s\n",getmsg);
I get something like this:
1TOKEN:c
2TOKEN:c
3TOKEN:b atob atobbody
read:a b atob atobbody
4TOKEN:b atob atobbody
You see how str kind of flows into getmsg. What happened there? How can I avoid this from happening?
Thanks in advance :)
in the code, "getmsg" is called "token", I thought it might have something to do with identical names or something so I changed it to getmsg, same error, so I changed it back...
if(buf[0]=='C'){
int login_error=1;
fp=fopen("r.txt","r");
if(fp!=NULL){
memcpy(&count,&buf[1],2);
pack.boxid=ntohs(count);
memcpy(pack.pword,&buf[3],10);
printf("boxid:%u pword:%s\n",pack.boxid,pack.pword);
while(fgets(str,250,fp)!=NULL){
/*"getmsg"===>*/ token=strtok(str," ");
token=strtok(NULL," ");//receiver uname
token1=strtok(NULL," ");//pword
token2=strtok(NULL," ");//boxid
sscanf(token2,"%hu",&count);//convert char[] to unsigned short
if(pack.boxid==count && strcmp(token1,pack.pword)==0){//uname & pword found
login_error=0;
printf("found:token:%s\n",token);
break;
}
}
if(login_error==1){
count=65535;
pack.boxid=htons(count);
}
if(login_error==0){
count=0;
pack.boxid=htons(count);
}
fclose(fp);
}
printf("1TOKEN:%s\n",token);
if(login_error==0){
int msg_error=1;
fp=fopen("m.txt","r");
fp1=fopen("m1.txt","w");
if(fp!=NULL && fp1!=NULL){
printf("2TOKEN:%s\n",token);
while(fgets(str,250,fp)!=NULL){
printf("3TOKEN:%s\n",token);
printf("read:%s",str);
token1=strtok(str," ");//sender
token2=strtok(NULL," ");//receiver
token3=strtok(NULL," ");//subject
token4=strtok(NULL," ");//body
printf("m.txt:token1:%s token2:%s token3:%s token4:%s\n",token1,token2,token3,token4);
if(msg_error==1 && strcmp(token,token2)==0){//message found
msg_error=0;
count=0;
pack.boxid=htons(count);
strcpy(pack.uname,token1);
strcpy(pack.subject,token3);
strcpy(pack.body,token4);
printf("pack:uname:%s subject:%s body:%s token:%s token2:%s strcmp:%d\n",pack.uname,pack.subject,pack.body,token,token2,strcmp(token,token2));
continue;
}
fprintf(fp1,"%s %s %s %s\n",token1,token2,token3,token4);
}
if(msg_error==1){
count=65534;
pack.boxid=htons(count);
}
printf("count:%u -> boxid:%u\n",count,pack.boxid);
fclose(fp);
fclose(fp1);
}
str[0]='c';
memcpy(&str[1],&pack.boxid,2);
memcpy(&str[3],pack.uname,8);
memcpy(&str[11],pack.subject,20);
memcpy(&str[31],pack.body,200);
str[231]='\0';
bytes=232;
}
}
below is m.txt, it is used to store senders, receivers, subjects and msgbodies: the naming patter is quite obvious >.^
a b atob atobbody
a c atoc atoccc
b c btoc btoccccc
b a btoa btoaaaaa
So I'm trying to get a msg stored in m.txt for the recipient "c", but it flows over, and by much coincidence, it returns the msg for "b"...
It looks like getmsg is pointing to the third character of your str buffer:
`str` is "a b atob atobbody"
^
|
\__ `getmsg` is pointing there.
Therefore, every time you change str by calling fgets(), the string pointed to by getmsg also changes, since it uses the same memory.