Question

Hi everyone I am running the following code on pseudo terminal /dev/pts/1 and I am tryin to read the contents from the terminal /dev/pts/2.

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

int main(){

char str[50];

int fd = open("/dev/pts/2",O_RDONLY);
str[read(fd,str,20)] = '\0';

printf("%s\n",str);


return 0;

}

anirudh@anirudh-Aspire-5920:~$ gcc test.c
anirudh@anirudh-Aspire-5920:~$ ./a.out
n
anirudh@anirudh-Aspire-5920:~$ 

On the terminal /dev/pts/2 I had typed “anirudh” however it showed “airudh” on that and the missing character n was displayed on the terminal /dev/pts/1.
However when I try to read from the terminal /dev/pts/1 I can read every character properly.
So I am not able to understand the behavior of this program. Please help me out. Thanks in advance. 🙂

Answer 1

First, you probably have another process reading from /dev/pts/2 and thus characters are send to it and not yours. Then the terminal is probably set in read “char per char” mode by that other process (that’s what some shell do), you are reading just one character.