ctermid

Purpose

     Generates a file name for terminal.

Library

     Standard I/O Library (libc.a)

Syntax

     #include <stdio.h>

     char *ctermid (s)
     char *s;

Description

     The  ctermid subroutine  generates the  path name  of the
     controlling terminal  for the current process  and stores
     it in a string.

     If  the s  parameter is  a  NULL pointer,  the string  is
     stored  in an  internal static  area and  the address  is
     returned.  The  next call to ctermid  overwrites the con-
     tents of the internal static area.

     If the s parameter is not  a NULL pointer, it points to a
     character array of at least L_ctermid elements as defined
     in the stdio.h  header file.  The path name  is placed in
     this array and the value of s is returned.

     The difference  between the  ctermid and  ttyname subrou-
     tines is  that ttyname must  be handed a  file descriptor
     and returns  the actual  name of the  terminal associated
     with that file descriptor, while ctermid returns a string
     (/dev/tty) that refers to the  terminal if used as a file
     name.  Thus ttyname is useful only if the process already
     has at least one file open to a terminal.

Related Information

     In this book:  "ttyname, isatty."