CODEWITHSUNDEEP
clinux
Miguel
Miguel

Reputation: 87

How to use read function to read from terminal input (stdin)?

The main function will be in an infinite loop reading the numbers that the user puts in the terminal and storing them on a buffer. My problem is that I need to read from terminal using this function:

read(int fd, void *buf, size_t count);

How can the file descriptor point to the terminal?! (I hope I'm not saying some barbarity)

Thanks in advance!

EDIT: I already took your advice, but something is missing. This is a small program that I wrote to test:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int buffer[5], i=0, j;

int main(){
   for(j=0; j<5; j++) buffer[j] = 0;
   while(i<5){
     read(STDIN_FILENO, buffer, 8);
     printf("->%d\n", buffer[i]);
     i++;
   }
   return 0;
}

Outup:

1
->2609
2
->0
3
->0
4
->0
5
->0

Why this doesn't print the numbers that I inserted?

Upvotes: 0

Views: 5933

Answers (4)

Jean-Baptiste Yun&#232;s
Jean-Baptiste Yun&#232;s

Reputation: 36391

On POSIX you can use symbols like STDIN_FILENO to represents the input of your application. But beware that the standard input is not always the terminal, especially when you redirect input/output via the shell.

Upvotes: 1

Michael Hampton
Michael Hampton

Reputation: 9980

By default the program's standard input is on file descriptor 0.

If you really mean to read from the terminal, instead of standard input, you can open() /dev/tty.

Upvotes: 2

edmz
edmz

Reputation: 8494

Your process has three file descriptors open since it has been spawned: STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO (0, 1, 2 respectively). These macros are defined in unistd.h.
read(STDIN_FILENO, buff, bytes)

Upvotes: 2

chrk
chrk

Reputation: 4215

stdin is fd 0,

stdout is fd 1, and

stderr is fd 2.

Upvotes: 1

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