a weird behavior of gets()

[28poGNh0]

when I execute it skeeps the name extraction like this way

Enter the information of student nbr
First name : Age :
if you notice I can not enter the name
thanks for reading

int main()
{
studentInfo *sInfo;
int sNbr;
cout << "Enter your the number of the students -> ";cin >> sNbr;
system("cls");

sInfo = new studentInfo[sNbr];

for(int i=0;i<sNbr;i++,sInfo++)
{
cout << "Enter the information of student nbr " << i+1 << endl;
cout << "First name : " ;gets(sInfo->name);
cout << "Age : " ;cin >> sInfo->age;
cout << "Gender : " ;cin >> sInfo->gender;cout << endl;
}sInfo-=sNbr;
for(int i=0;i<sNbr;i++,sInfo++)
{
cout << "Information of student nbr " << i+1 << endl;
cout << "First name is : " << sInfo->name << endl;
cout << "Age is : " << sInfo->age << endl;
cout << "Gender is : " << sInfo->gender << endl << endl;
}
delete sInfo;
return 0;
}

[28poGNh0]

I forgot the head of the program
thans again

# include <iostream>
# include <cstdio>
# include <cstdlib>
using namespace std;

struct studentInfo
{
char name[20];
int age;
char gender;
};

[28poGNh0]

No solutions ?!

[Moschops]

gets will read from stdin until it finds a newline. You are leaving a newline there from previous operations, so it reads that in straightaway without you having to put any new data into the input buffer.

If you compile your code using g++, you even get warned about how bad gets is:

warning: the `gets' function is dangerous and should not be used.

Bad solution:

# include <iostream>
# include <cstdio>
# include <cstdlib>
using namespace std;

struct studentInfo
{
char name[20];
int age;
char gender;
};


int main()
{
studentInfo *sInfo;
int sNbr;
cout << "Enter your the number of the students -> ";cin >> sNbr;


sInfo = new studentInfo[sNbr];

for(int i=0;i<sNbr;i++,sInfo++)
{
cout << "Enter the information of student nbr " << i+1 << endl;
cout << "First name : " ;

 int ch;
while ((ch = getchar()) != '\n' && ch != EOF);

gets(sInfo->name);
cout << "Age : " ;cin >> sInfo->age;
cout << "Gender : " ;cin >> sInfo->gender;cout << endl;
}sInfo-=sNbr;
for(int i=0;i<sNbr;i++,sInfo++)
{
cout << "Information of student nbr " << i+1 << endl;
cout << "First name is : " << sInfo->name << endl;
cout << "Age is : " << sInfo->age << endl;
cout << "Gender is : " << sInfo->gender << endl << endl;
}
delete sInfo;
return 0;
}

Good solution: DON'T USE gets

[28poGNh0]

Thank you so much reading

but can I ask what those lines do

int ch;
while ((ch = getchar()) != '\n' && ch != EOF);

[Moschops]

int ch; Create a new int variable, named ch.

while ((ch = getchar()) != '\n' && ch != EOF);
Read in using the getchar function and store the input into the variable ch nutil it's the end of a line or the end of a file.

Don't use gets.

[ankit2313]

sorry to ask but i'd like to ask you Moschops that why did u use EOF when there is no file issue in the program just !='\n' is sufficient.

[Moschops]

It's generic input buffer flushing code. Since it's a bad solution anyway, it didn't really seem important.

[Cubbi]

It's important anyway: a user could enter EOF from keyboard and get this program stuck in an endless loop (although abusing gets() to read OP's passwords would be a more profitable use of the input access)

[ne555]

¿where is that endless loop? EOF will break the while
@Moschops, please indent your code.

[Cubbi]

@ne555 I meant that in response to @ankit2313's "why did u use EOF [...] just !='\n' is sufficient" but yes, I was thinking C++ for a bit there. getchar()'ing a EOF'd stdin does not always return immediately (like cin.get()'ting a eof'd cin) : the outcome depends on the OS and probably terminal settings.
Without the EOF check, it loops forever on my Solaris, but reads the following characters on my AIX or Linux.

[28poGNh0]

The program works perfectly well , thanks to you Moschops ,but I have couple of questions:

the first one is : I have a hard time to understand the relation between the while loop and gets() ,
I think the while loop dose not ends until It gets a caractere different than '\n' or EOF,then gets the name , am I right?