Scanf not skipping when I press Enter - c

Question

The following piece of code is continuously asking for me to give it 1 input, meaning that when I press "Enter" it does not skip to the next scanf instead just goes to the next line on console and waits for input.
int main()
{
int i, print, line ;
char oFile[50] , iFile[50] = "listsource.c" ;
printf("Please enter the name of the input file: ") ;
scanf("%s", iFile) ;
printf("Please enter 0 to print to console, 1 to print to another file: ") ;
scanf("%d", &print) ;
printf("%s", iFile) ;
}
I am trying to give it a default value of "listsource.c" if no input is entered, have already tried fgets and I have the same problem

Answer 1

Try this:
#include <stdio.h>
int main()
{
char hello[81];
fgets(hello, 80, stdin);
hello[strlen(hello) - 1 ] = '\0';
// OR
gets(hello);
}
It worked with Online C Compiler.
You will have to strip the newline although...gets() will do the work, but is it dangerous as it will read any number of character regardless of the amount specified by you when you declared the variable it is going into. Thus it will overwrite past the memory allocated by the compiler. (Yes, this is allowed by C. In C, the programmer is expected to know what he is doing, so he gets all the powers he wants!)

Answer 2

All scanf() conversion specifiers except "%c", "%[..]" and "%n" ignore leading whitespace. A '\n' is whitespace. Using scanf() you can press Enter until your finger falls off using the "%d" conversion specifier and it will never be read. scanf() will simply discard all whitespace and continue blocking waiting on valid input or EOF.
That is just one, of the many, many pitfalls scanf() has for new C programmers. That is why it is highly recommended that you use fgets() for ALL user input. With a sufficient size buffer (character array), fgets() will consume an entire line-at-a-time (including the trailing '\n'). This greatly simplifies input because what remains in stdin after the user presses Enter does not depend on whether a scanf() matching-failure occurred.
To remove the trailing '\n' from the end of the buffer filled by fgets(), simply use strcspn() as follows:
iFile[strcspn (iFile, "\n")] = 0; /* trim \n from end of iFile */
If you do need to convert the contents of your buffer, simply use sscanf() providing your buffer as the first argument, the remainder just as you would use scanf() -- but on any failure, nothing is left in stdin because you have completely read the user-input with fgets().
If you had attempted to read an int with scanf() and the user slipped and hit 'r' reaching for '4', then a matching-failure occurs and character extraction from stdin ceases leaving 'r' in stdin unread. If you are taking input in a loop -- you have just created an infinite loop...
In your case here asking the user to enter 0 or 1, there is no need for numeric conversion to begin with. Simply read the input into a buffer with fgets() and then check if the first character in the buffer is '0' or '1' (the ASCII digits). No conversion required.
Don't use MagicNumbers (e.g. 50) in your code. If you need a constant, #define one, or use a global enum to accomplish the same thing, e.g.
#define MAXFN 50 /* if you need a constant, #define one (or more) */
#define MAXC 1024
int main (void)
{
char buf[MAXC], /* oFile[MAXFN] ,*/ iFile[MAXFN];
(note: if programming on a microcontroller, reduce the max number of characters for your read-buffer (MAXC) accordingly, otherwise, for general PC use a 1K buffer is fine)
Putting it altogether, and adding a "print to another file - not implemented", to handle the user entering 1 as asked, you could do:
#include <stdio.h>
#include <string.h>
#define MAXFN 50 /* if you need a constant, #define one (or more) */
#define MAXC 1024
int main (void)
{
char buf[MAXC], /* oFile[MAXFN] ,*/ iFile[MAXFN];
fputs ("Please enter the name of the input file: ", stdout);
if (!fgets (iFile, MAXFN, stdin)) { /* read ALL user input with fgets() */
puts ("(user cancled input)"); /* validate, if manual EOF return */
return 0;
}
iFile[strcspn (iFile, "\n")] = 0; /* trim \n from end of iFile */
for (;;) { /* loop continually until valid input from user or EOF */
fputs ("\nPlease enter 0 to print to console, "
"1 to print to another file: ", stdout);
if (!fgets (buf, MAXC, stdin)) { /* read ALL user input with fgets() */
puts ("(user cancled input)"); /* validate, if manual EOF return */
return 0;
}
if (*buf == '0') { /* no need to covert to int, just check if ASCII '0' */
puts (iFile);
break;
}
else if (*buf == '1') { /* ditto -- just check if ASCII '1' */
puts ("print to another file - not implemented");
break;
}
fputs (" error: invalid input, not 0 or 1\n", stderr); /* handle error */
}
}
(note: when you need the user to provide specific input, loop continually until you get what you require, or until the user generates a manual EOF by pressing Ctrl + d (or Ctrl + z on windows))
Example Use/Output
Intentionally pressing Enter alone for the first input and providing invalid input for the next two, you would have:
$ ./bin/console_or_file
Please enter the name of the input file: myInputFilename.txt
Please enter 0 to print to console, 1 to print to another file:
error: invalid input, not 0 or 1
Please enter 0 to print to console, 1 to print to another file: bananas
error: invalid input, not 0 or 1
Please enter 0 to print to console, 1 to print to another file: 2
error: invalid input, not 0 or 1
Please enter 0 to print to console, 1 to print to another file: 0
myInputFilename.txt
Look things over and let me know if you have further questions.