fgets() doesn't read string correctly

[dolgion1]

Hi people, i have a problem with the fgets() function, or rather actually scanf.


scanf("%d",&n);
fflush ( stdin );
fgets(line,sizeof(line),stdin);

[ray bot]

If line is a char array, then shouldn't that last statement be fgets(line, strlen(line), stdin);

[dolgion1]

no that doesnt solve it
(btw sorry for the double post)

[yabbadabbadont]

Please provide all the relevant code, not just a snippet.

[Compyx]

LIke Yabbadabbadont said, post your code. My guess is you've declared line as a pointer to char, rather than a array of char.

With line as a pointer to char, sizeof(line) yields the size of the pointer, not the size of the memory pointed to by line. So on my 32-bit system fgets() would read at most 3 chars from stdin.

But without seeing the actual code in question, this is all just guess-work. Also loose the parentheses, the sizeof operator only needs those when applied to a type, when applied to an object you don't need them, they only obscure your code.

[dolgion1]

okay here is some complete code that ive written to
test out the problem with using scanf right before using fgets:

#include <stdio.h>

int main()
{
char array[10];
int number;
scanf("%d",&number);
fgets(array,sizeof(array),stdin);
printf("%s\n",array);
return 0;
}

ive tried using fflush(stdin); between scanf and fgets, but that somehow doesn't change anything. i use the gcc compiler in the ubuntu terminal. a friend of mine got that code working without problems on visual c++ in windows, but i dont believe that this could be solely a linux related problem

ill be thankful for any help

[LaRoza]

It does work, just don't put a newline before the string.



laroza@laroza-desktop:~$ ./p.c
1 me
me

laroza@laroza-desktop:~$


(I am using a C interpreter, but it will work the same when compiled)

[Jessehk]

You shouldn't be fflush()'ing an input stream -- the standard doesn't dictate what it will actually do.

You should also avoid using scanf to read the integer. Read in a string with fgets and then convert it to an integer using sscanf (the two s's are intentional). I can provide an example if it would help.

All of those functions can fail. You need to be checking return values in order to check for errors.

C is difficult and there are lots of little quirks -- you need to be aware of them.

[opipa]

What I did is to put fgets() before scanf(), so that the last input of scanf (normally a NEWLINE) doesn't go to fgets. Just my speculation. I am working under gcc as well.

[dwhitney67]

What I did is to put fgets() before scanf(), so that the last input of scanf (normally a NEWLINE) doesn't go to fgets. Just my speculation. I am working under gcc as well.

Read this: http://www.flamewarriors.com/warriorshtm/necromancer.htm

[slavik]

we don't resurrect things here.