/* setecho.c *   usage:  setecho [y|n] *   shows:  how to read, change, reset tty attributes */#include        <stdio.h>#include        <termios.h>#define  oops(s,x) { perror(s); exit(x); }main(int ac, char *av[]){        struct termios info;        if ( ac == 1 ) 		exit(0);        if ( tcgetattr(0,&info) == -1 )          /* get attribs   */		oops("tcgettattr", 1);        if ( av[1][0] == 'y' )                info.c_lflag |= ECHO ;          /* turn on bit    */        else                info.c_lflag &= ~ECHO ;         /* turn off bit   */        if ( tcsetattr(0,TCSANOW,&info) == -1 ) /* set attribs    */               oops("tcsetattr",2);}