segmentation fault when using strtok

[krista]

Hi,

I am beginner of C++. When I try to read a file and put it into X and
Y variables. I got that segmentation fault.
the data file is
data.txt:
4.4 6.8
3.2 -5.5
3.3 0.9

I just want to print out the file as target: 4.4,6.8
target: 3.2,
-5.5........

I already can read the file
but i cannot separate the data in a line from the file to x and y
variables

the code is

ifstream in;
in.open(data.txt);
char str[100];
while (!in.eof()){
in>>str;
double X=atof(strtok(str," ");
double Y=atof(strtok(NULL," ");
cout<<"Target:"<< X << " "<< Y <<endl;
}

then the result is segmentation fault.

Please advise.

Krista

[trojanfoe]

On 22 Jan, 05:43, krista <[e-mail]:

Hi,

I am beginner of C++. When I try to read a file and put it into X and
Y variables. I got that segmentation fault.
the data file is
data.txt:
4.4 *6.8
3.2 *-5.5
3.3 0.9

I just want to print out the file as target: 4.4,6.8
* * * * * * * * * * * * * * * * * * * * * * * *target: 3.2,
-5.5........

I already can read the file
but i cannot separate the data in a line from the file to x and y
variables

the code is

ifstream in;
in.open(data.txt);
char str[100];
while (!in.eof()){
in>>str;
double X=atof(strtok(str," ");
double Y=atof(strtok(NULL," ");
cout<<"Target:"<< X << " "<< Y <<endl;

}

then the result is segmentation fault.

Please advise.

Krista

Although I'm not a regular here, I have to say I don't think this is a
C++ question as strtok is part of the C runtime library, not C++
library. Also the program you have posted won't compile (missing
brackets after the atof/strtok combos).

Personally I have hardly ever used strtok, preferring to use sscanf
where I can validate that it returns 2 and perform the whole line
parsing in one shot:

float X, Y;
if (sscanf(line, "%f %f", &X, &Y) != 2)
{
say_something_prickly_to_the_user();
}

Andy

[red floyd]

krista wrote:

Hi,

I am beginner of C++. When I try to read a file and put it into X and
Y variables. I got that segmentation fault.
the data file is
data.txt:
4.4 6.8
3.2 -5.5
3.3 0.9

I just want to print out the file as target: 4.4,6.8
target: 3.2,
-5.5........

I already can read the file
but i cannot separate the data in a line from the file to x and y
variables

the code is

ifstream in;
in.open(data.txt);
char str[100];

The following loop does not do what you think it does. See FAQ 15.5,
http://parashift.com/c++-faq-lite/in....html#faq-15.5

while (!in.eof()){
in>>str;
double X=atof(strtok(str," ");
double Y=atof(strtok(NULL," ");
cout<<"Target:"<< X << " "<< Y <<endl;
}

then the result is segmentation fault.

Please advise.

Krista

[Jim Langston]

krista wrote:

Hi,

I am beginner of C++. When I try to read a file and put it into X and
Y variables. I got that segmentation fault.
the data file is
data.txt:
4.4 6.8
3.2 -5.5
3.3 0.9

I just want to print out the file as target: 4.4,6.8
target: 3.2,
-5.5........

I already can read the file
but i cannot separate the data in a line from the file to x and y
variables

the code is

ifstream in;
in.open(data.txt);
char str[100];
while (!in.eof()){
in>>str;
double X=atof(strtok(str," ");
double Y=atof(strtok(NULL," ");
cout<<"Target:"<< X << " "<< Y <<endl;
}

then the result is segmentation fault.

You do not need to use strtok to do what you want.

Consider (untested) code:

ifstream in("data.txt");
double X = 0;
double Y = 0;
while ( in >X >Y )
{
cout << "Target" << X << " " << Y << endl;
}

--
Jim Langston
ta*******@rocketmail.com