how can I use scanf() to read a file including space in C

Question

I am not allowed to call any function other in a C library other than scanf, printf, and feof. When I try to use the code below, it only reads a file up to space char. Is there a way to read a whole line without using "%[^\n]"? My end goal is to read the entire file using feof file but first, I need to know how to read a line using scanf. Is it possible?

#include <stdio.h>
int main(){

  char ar[50];

  scanf("%s", ar);
  printf("%s", ar);

}

The only way to get `scanf` to read a whole line at a time is with `"%[^\n]"`. At the other extreme, you can read one character at time with `scanf("%c", &input_char)`. In that case, it's basically the same as calling `getchar`. — user3386109, Sep 23 '20 at 01:27
BTW, [don't use feof](https://stackoverflow.com/questions/5431941). The return value from `scanf` tells you when you've reached the end-of-file. `feof` doesn't provide any information that `scanf` doesn't already provide. — user3386109, Sep 23 '20 at 01:30
The correct way to read a file a line at a time in standard C is with `fgets`. Your instructor is wrong to forbid you to use `fgets`, and you may tell them I said so. Moreover, you may tell them I said [`scanf` should never be used at all](https://stackoverflow.com/questions/15664664/scanf-regex-c/15664816#15664816). — zwol, Sep 23 '20 at 01:30
how can I make a loop to read one line at a time without fgets? — mico, Sep 23 '20 at 02:10
@user3386109 `"%[^\n]"` fails to read a whole line aside form not reading the `'\n'`, is reads/saves nothing when the line is only `"\n"`. Lacking a width limit, it is bad like `gets()`, and worse. — chux - Reinstate Monica, Sep 23 '20 at 02:36
@chux I didn't say it was a good idea, only that it's the only way to read a whole line with one call to `scanf`. The OP had already said that using `"%[^\n]"` was not an option, so I didn't bother with adding all the fine print, caveats, and dire warnings. — user3386109, Sep 23 '20 at 07:48
Detail: " only way to read a whole line with one call to scanf" --> STL has "... each line consisting of zero or more characters plus a terminating new-line character.". `"%[^\n]"` does not read a whole line, just most of it as it fails to read the last character of the line. `"%[^\n]%*c"` reads a whole line, except a line like `"\n"`. `scanf()` lacks a single format that reads all lines. — chux - Reinstate Monica, Sep 23 '20 at 12:44

chux - Reinstate Monica · Answer 1 · 2020-09-23T02:44:15.500

1

Read one character at a time.

#include <stdio.h>
int main(void) {
  char ch;
  while (scanf("%c", &ch) == 1) {
    printf("%c", ch);
  }
}

P. S. Don't ever do this for production code and never admit your did this on a résumé.

Follow @zwol advice.

"My end goal is to read the entire file using feof file " --> Why is “while ( !feof (file) )” always wrong?.

edited Sep 23 '20 at 02:44

answered Sep 23 '20 at 02:38

chux - Reinstate Monica

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how can I use scanf() to read a file including space in C

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