What happens on opening /dev/tty failure?

Applications Programming
1

Since the existence of /dev/tty is not guaranteed, what happens when an attempt is made to open /dev/tty and there's no controlling terminal?

Will it fail, or open /dev/null instead? Or do something else?

So is checking for NULL in the code below a safe way of checking whether opening /dev/tty was sucessful? If not how should it be checked?

FILE* fp = fopen("/dev/tty", "r");
if (fp == NULL)
    OopsBetterDoSomething();

int c = fgetc(fp);
fclose(fp);

Many thanks all.

2

Checking to see that the stream pointer is NULL/not NULL is okay.

What happens in the case that stdin is redirected, which is, I think, what you may want.
try something like this:

File *in=NULL;
if( isatty(0) ) 
   in=fopen("dev/tty", "r");  
else
  in=stdin;
if(in==NULL) 
   barf();

Your best bet is to refer to Steven's "Advanced Programming in the UNIX Environment"

3

Thanks Jim.

The code I posted is the code to handle 'what happens if stdin is redirected'. My call to isatty() is just above the snippet I posted. :slight_smile:

Cheers.