why I can't get a string from getchar()

Question

I want to get a string by calling function getchar(), but there is something wrong. Below is my code

int i, j, t;
char a[N], *p = argv[1];
for (i=0; i<5; a[i]=t, i++){
    if ((t = getchar()) == EOF) break;
}
a[i] = 0;

The initial value of `t` gets stored before it is assigned a value. There is no need to stuff this in to the `for` loop; a simple reordering fixes this. — Jongware, May 26 '15 at 11:31
What happens when you build the code? What happens when you run it? For some specific input, what is the expected and actual output? — Some programmer dude, May 26 '15 at 11:31
What's wrong in that? (except for unused `j`, `*p` and `argv` and undefined `N`) — Aki Suihkonen, May 26 '15 at 11:33
What is `N`? I can't see any problem if it is large enough.. — Eugene Sh., May 26 '15 at 11:37
You have undefined behaviour the first time you read from `t`. — juanchopanza, May 26 '15 at 11:38
@CoolGuy; I fail to see that. `t = getchar();` is executed before `a[i]=t;` — Aki Suihkonen, May 26 '15 at 11:38

Sourav Ghosh · Answer 1 · 2015-05-26T11:38:13.020

2

Your code depends on the value of N. So, change your code like

#define N 20      //my assumption

int i, t;

char a[N];   // *p = argv[1]; no relevant for this example

for (i=0; i < N-1; i++){  //check here
    if ((t = getchar()) == EOF) break;
    a[i]=t;
}
a[i] = 0;

Remeber, array index in C is 0 based.

edited May 26 '15 at 11:38

answered May 26 '15 at 11:30

Sourav Ghosh

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And then add the 0 terminator to the end of the array. – John Bode May 26 '15 at 11:31
I want to know why it don`t stop after i press "Enter". I think that the code depends on eight the value of N or the enter. – Huichuang Xuanyuan May 26 '15 at 11:49
1

@HuichuangXuanyuan `ENTER`? why it will stop on `ENTER`? the breaking condition is `EOF`, press `CTRL+D` (on linux). – Sourav Ghosh May 26 '15 at 11:50

why I can't get a string from getchar()

1 Answers1