QUestion on gets

[AvaGodess]

Ok had this question from my friend. basically he's scanning info from keyboard to an array of structures. But here's the thing, he started using scanf which works fine but then there is a scenario that imagine the address has a space between, so he used gets for that section. However, now the program compiles but when it reaches that section it skips that area and goes to the next section. Whats the problem there?


printf("\nEnter First Name A Customer: " );
scanf("%s", data[i].fname ); /* Read the horse's name */
printf("\nEnter %s's Last Name: ", data[i].fname );
scanf("%s", data[i].lname );
printf("\nEnter %s's Street Address: ", data[i].fname );
gets(data[i].staddress);
printf("\nEnter Country Location of %s: ", data[i].fname );
scanf("%s",data[i].country );

however, if you use scanf it works good, but the gets is skipped. how can it be fixed.

[master5001]

Don't even use gets(). Use fgets().

[AvaGodess]

Don't even use gets(). Use fgets().

Well i did try fgets like this fgets(data[i].staddress,sizeof(data[i].staddress),stdin); but i still got the same result as using gets

[master5001]

I wasn't even trying to answer your question. Just fix something dubious in your code. Is it perhaps possible that scanf() is your problem? I.e. it is not pulling in the input the way you desire.

[AvaGodess]

I wasn't even trying to answer your question. Just fix something dubious in your code. Is it perhaps possible that scanf() is your problem? I.e. it is not pulling in the input the way you desire.

lol, ok. Well matt its on the gets, when running the program it simply skips the gets, and i got no idea why, it goes to the next scanf that follows.

[master5001]

Check it out though, if you have scanf() leave crap in the input stream, you may end up having your subsequent call to fgets() not work as planned. To fight this you could always call fgets() and use sscanf() to read from the line that you read in with fgets().

Also, and kind of unrelated but still important: Your scanf("%s", variable) lines are prone to buffer overflow. You should do something like scanf("%10s", variable) or whatever sizeof variable happens to equal.

[AvaGodess]

Check it out though, if you have scanf() leave crap in the input stream, you may end up having your subsequent call to fgets() not work as planned. To fight this you could always call fgets() and use sscanf() to read from the line that you read in with fgets().

Also, and kind of unrelated but still important: Your scanf("%s", variable) lines are prone to buffer overflow. You should do something like scanf("%10s", variable) or whatever sizeof variable happens to equal.

thank you, yes the buffer had trash, used fflush() to clear out the contents, got it working, we can call this closed now, thanks Matt,Aria said ud help, lol

[master5001]

Yeah no problem.

Using fflush() on stdin is actually undefined according to the standard. If you want to do it the right way I would do it like this:

Example:

char line[4096]; /* 4k is a large enough line, methinks */

printf("\nEnter First Name A Customer: " );
fgets(line, sizeof line, stdin);
sscanf(line, "%s", data[i].fname ); /* Read the horse's name */
printf("\nEnter %s's Last Name: ", data[i].fname );
fgets(line, sizeof line, stdin);
sscanf("%s", data[i].lname );
printf("\nEnter %s's Street Address: ", data[i].fname );
fgets(data[i].staddress, sizeof data[i].staddress, stdin);
printf("\nEnter Country Location of %s: ", data[i].fname );
fgets(line, sizeof line, stdin);
sscanf("%s",data[i].country );

[Elysia]

Tsch, you know as well as I that that code is no better than the original.
There are several examples to get rid of the trailing newline, and sscanf is probably the worst of those alternatives, especially when buffer sizes go unspecified.

[AvaGodess]

Tsch, you know as well as I that that code is no better than the original.
There are several examples to get rid of the trailing newline, and sscanf is probably the worst of those alternatives, especially when buffer sizes go unspecified.

And what would u recommend then Elysia!

[matsp]

One of these:

strtok(str, "\n");

or

p = strchr(str, '\n');
if (p) *p = '\0';

or

len = strlen(str);
if (str[len-1] == '\n')
    str[len-1] = '\0';

You may also want to consider the case when there isn't a newline in that place, and what you should do then (it means that the buffer wasn't big enough).
--
Mats

[AvaGodess]

One of these:
You may also want to consider the case when there isn't a newline in that place, and what you should do then (it means that the buffer wasn't big enough).
--
Mats

Mats you see, last night it was working on gets but that was on windows, when i tried it on ubuntu it still does what it was doin in the beginning. Im not sure if its what u guys say about the newline character, the problem it does is it skips the first input with fgets. Take a look:

printf("\nEnter Customer's Name: " );

       scanf("%s", data[i].fname ); /* Read the horse's name */

       printf("Enter %s's Last Name: ", data[i].fname );

       scanf("%s", data[i].lname );

       printf("Enter %s's Age: ", data[i].fname );

       scanf("%d", &data[i].age );

       printf("Enter %s's Date Of Birth:Format(28/06/89): ", data[i].fname );

       scanf("%d", &data[i].day );

       printf("\r\r");

       scanf("%d",&data[i].month);

       printf("\r\r");

       scanf("%d",&data[i].year);

       printf("Enter %s's Street Address: ", data[i].fname );

       fflush(stdin);

       fgets(data[i].staddress,sizeof (data[i].staddress),stdin);

       printf("Enter Country Location of %s: ", data[i].fname );

       fflush(stdin);

       fgets(data[i].country,sizeof (data[i].country),stdin );

Is it there garbage in the stdin?

[matsp]

Ah, sorry. I thought we were talking about getting rid of the newline that sits inside the buffer when you use fgets().

I would suggest that you do not MIX fgets() and scanf() - it will fail sooner or later. Use fgets() to read the data, then use sscanf() if you need to get integer/float data out of the input string. If you need text input, use the above tricks to remove the newline at the end of your input [most likely, you do not want that].

As stated fflush(stdin) doesn't work to remove newlines (or other stuff) from the input in all systems - it only works in Turbo C and Microsoft C as far as I'm aware. Certainly not in Linux.

--
Mats

[AvaGodess]

Ah, sorry. I thought we were talking about getting rid of the newline that sits inside the buffer when you use fgets().

I would suggest that you do not MIX fgets() and scanf() - it will fail sooner or later. Use fgets() to read the data, then use sscanf() if you need to get integer/float data out of the input string. If you need text input, use the above tricks to remove the newline at the end of your input [most likely, you do not want that].

As stated fflush(stdin) doesn't work to remove newlines (or other stuff) from the input in all systems - it only works in Turbo C and Microsoft C as far as I'm aware. Certainly not in Linux.

--
Mats

Cool, thats something new for me today. I guess thats why it works on windows and not on ubuntu then. So what u are suggesting is to follow something like what Matt did on his post, before Elysia right. Ill try that.

[matsp]

Yes, but don't use scanf() to read out string data. If you feel that you need to read into a large buffer and then crop it off, use strncpy. Otherwise, you can read into the actual buffer. In both cases, you need to make sure you remove the newline that is at the end of the input. [if there isn't one, the data you received is too long to fit in the buffer, and you probably should care about that case in a proper application - but I'll leave that to you to decice].

--
Mats