Difference between scanf(“%c”, &c) and scanf(” %c”, &c) [duplicate]

by

The difference between scanf("%c", &c1) and scanf(" %c", &c2) is that the format without the blank reads the next character, even if it is white space, whereas the one with the blank skips white space (including newlines) and reads the next character that is not white space.

In a scanf() format, a blank, tab or newline means ‘skip white space if there is any to skip’. It does not directly ‘clear the input buffer’, but it does eat any white space which looks similar to clearing the input buffer (but is quite distinct from that). If you’re on Windows, using fflush(stdin) clears the input buffer (of white space and non-white space characters); on Unix and according to the C standard, fflush(stdin) is undefined behaviour.

Incidentally, if you typed the integer followed immediately by a carriage return, the output of your program ends with two newlines: the first was in c and the second in the format string. Thus, you might have seen:

$ ./your_program
123
int=123
char=

$

That is, the scanf() reads the newline as its input. Consider an alternative input:

$ ./your_program
123xyz
int=123
char=x
$

The integer input stopped when it read the ‘x’; the character input therefore reads the ‘x’.

More Related Contents:

  1. isnt everything where it should be, why the segmentation fault?
  2. How do you allow spaces to be entered using scanf?
  3. C: Multiple scanf’s, when I enter in a value for one scanf it skips the second scanf [duplicate]
  4. Program doesn’t wait for user input with scanf(“%c”,&yn);
  5. C/C++ printf() before scanf() issue
  6. Using “\n” in scanf() in C [duplicate]
  7. What does the scanf function return?
  8. How to read string from keyboard using C?
  9. Does scanf() take ‘\n’ as input leftover from previous scanf()?
  10. What is the difference between sscanf or atoi to convert a string to an integer?
  11. read comma-separated input with `scanf()`
  12. string format for intptr_t and uintptr_t
  13. difference between %ms and %s scanf
  14. Reading a single character in C
  15. Why does a space in my scanf statement make a difference? [duplicate]
  16. Scanf won’t execute for second time
  17. Why doesn’t scanf need an ampersand for strings and also works fine in printf (in C)?
  18. scanf ignoring, infinite loop
  19. scanf() variable length specifier
  20. How can I scan strings with spaces in them using scanf()? [duplicate]
  21. Max string length using scanf -> ANSI C
  22. scanf not working as expected
  23. Get scanf to quit when it reads a newline?
  24. C – trying to read a single char from stdin (and failing) w/ scanf / getchar
  25. Program doesn’t execute gets() after scanf(), even using fflush(stdin)
  26. Why is adding a leading space in a scanf format string recommended?
  27. If statements not working?
  28. SegFault after scanf?
  29. C programming – Loop until user inputs number scanf
  30. Difference between scanf() and fgets()

Leave a Comment