simple c programming problem

i have a very silly problem with c programming in linux.i have red hat 6.2 linux version.and whenever i am writing a code for accepting a single character its not accepting it, rather it is skiping the value.i also used fflush(stdin),but problem not solved.the same code runs perfectly in TC(dos based).what can be the problem can any one tell me?



i used scanf and getchar both but these both never worked

Originally posted by abi_sh i have a very silly problem with c programming in linux.i have red hat 6.2 linux version.and whenever i am writing a code for accepting a single character its not accepting it, rather it is skiping the value.i also used fflush(stdin),but problem not solved.the same code runs perfectly in TC(dos based).what can be the problem can any one tell me?

how about using getchar()?

which is the function you used to get the character?

yeah i have treid getchar() also it doesnt' work even then.

hi abi_sh,
yes it is the problem in linux. fflush(stdin) doesn't work in linux.
the reason why it is skipping that getting of char is there might be something garbage in stdin buffer. the garbage is due to previous scanf()'s or gets()'s before getchar(). so always use fgets() instead of scanf()'s and getchar()'s.
now try to replace to scanfs()'s and gets()'s with fgets();
if you are in need of formatted input , now try to format the input using atoi() or strtod() or something else.
now use getchar(), i hope there won't be problem.

When removing garbage you should also remember that in DOS/Windows end of line is 2 characters, when in Unix world it's only 1 character long.

hi edreddy
i tried the fgets() function also but it doesn't work it is giving me a error saying that missing parameters or something,well as far as i know fgets is used with FILE pointer right ,it takes file pointer.
if u don't mind can u write a small code with this fgets() and show how to use it?

Try something like
#include <stdio.h>
main(){
char a;
a=fgetc(stdin);
printf("%c\n",a);
}
--Sarin

Here is a code example of how to use getchar(). It is pretty much the same as the fgetc example above.

#include <stdio.h>
#include <unistd.h>

main()
{
   char c = (char) NULL;

   while ( 1 )
   {
      c = getchar();
      if ( c != -1 )
         printf("Hey there\n");
      usleep(100);

   }  // end while
}

fgets example:

#include <stdio.h>
#include <fnmatch.h>
#include <unistd.h>

#define BUFF_SIZE 256
main()
{
   char szInputBuffer[BUFF_SIZE + 1];
   int iMatch = 0;

   fgets( szInputBuffer, BUFF_SIZE, stdin );

   if (( strncasecmp( "y", szInputBuffer, 1 ) == 0) ||
       ( strncasecmp( "yes", szInputBuffer, 3 ) == 0))
   {
      iMatch = 1;
   }
   printf("String is [%s]; iMatch is [%d]\n", szInputBuffer, iMatch );
}

The problem when you have to press enter to get single character input is actually a terminal problem and not a fgetc or getchar error. Most terminals by default are in canonical mode, meaning that you have to press enter to send the input line. You can turn off canonical mode into ways.

Using stty:

stty -icanon

Run the first example above, before and after running stty.

Change conon setting with a program:
Best read in the UNIX FAQ:
http://www.erlenstar.demon.co.uk/unix/faq_4.html#SEC49