print string got by C getchar function

Question

I was testing one of simple getchar() function on GNU compiler, but why not get expected output

mto@ubuntu:~/c$ ./a.out 
agc

mto@ubuntu:~/c$

code as following :

#include <string.h>
#include "stdio.h"
#define MAX 80
int main()
  {
        char  ch, buffer[MAX+1];
        int x=0 ;
        while ((ch =getchar() != '\n') && x<MAX)
                buffer[x++]= ch;
         buffer[x]= '\0';

 int len = strlen(buffer);

for (int c=0; c< len; c++)
       printf("%c" , buffer[c]);
       return 0;

}

Please format your code consistently before asking people to look at it. — Tom Karzes
– Tom Karzes, Commented Oct 9, 2017 at 16:21
This (ch = getchar() != '\n') should be (ch = getchar()) != '\n'. You assign the result of the comparison to ch, but you want to assign the character. — M Oehm
– M Oehm, Commented Oct 9, 2017 at 16:25

P.P · Accepted Answer · 2017-10-09 16:25:27Z

2

while ((ch =getchar() != '\n') && x<MAX)

should be

while (((ch = getchar()) != '\n') && x<MAX)

Notice the extra ( .. ) around the assignment. ch =getchar() != '\n' is equivalent to and evaluated as ch = (getchar() != '\n') due to operator precedence. != has higher precedence than =(assignment).

answered Oct 9, 2017 at 16:25

P.P

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