stty related

1. stty: 虚终端设备控制命令。 
stty option operation

echo [-echo] Echoes [does not echo] the typed characters; The default is echo.
raw [-raw]    Disables [enables] the special meaning of the metacharacters ( ?, *, [list], [!list]); the default is -raw.
intr     Generates an interrupt signal; usually the [Del] key is used.
erase     (backspace) Erases the preceding character; usually the [ # ] key is used.
kill     Deletes the entire line; usually [ @ ] or [Ctrl u] is used.
eof     Generates the (end-of-file) signal from the terminal; usually [Ctrl-d] is used.
ek     Resets the erase and kill keys to [#] and [@] respectively.
sane     Sets the terminal characteristics to sensible default values.

2. Example of stty commands

$ stty -echo     #Turns echoing off
$ stty echo     #Turns echoing back on
$ stty \^u         #Now [Ctrl u] is the kill key
$ stty sane         #Reset options to reasonable values
When you have changes the options too many times and lost track of your changes, the sane option comes to your rescue.
$ stty ek         #Change the kill and erase keys to their default values. This command sets the kill to [@] and the erase key to [#]
bash --noediting    #entering a non-editing bash subshell
stty -a |egrep -o '\
stty erase X        #set erase 'X' key, this change is stick to dvices
stty erase @ echo         #set erase @,and set echo on
stty -a |egrep -o '\
stty erase ^H            #reset backspace
stty icrnl             #cause input carriage return to be converted to newline character
stty -icrnl         #
stty onlcr            #add carriage return to newline character
stty -onlcr            #
bash --noediting;stty -icanon    #disable canonical mode
stty icanon        #able buffering of input in the terminal

3.  showtty.c

#include <apue.h>
#include <termios.h>

/* mapping of flag bit position to name */
struct flaginfo
{
    int fl_value; //flag value
    char *fl_name; //string describing flag
    };

/* Mapping of index to description */
struct cc_entry{
    int index;
    char *description;
    };


struct flaginfo input_flags[]={
    {IGNBRK, "Ignore break condition"},
    {BRKINT, "Signal interrupt on break"},
    {IGNPAR, "Ignore chars with parity errors"},
    {PARMRK, "Mark parity errors"},
    {INPCK, "Enable input parity check"},
    {ISTRIP, "Strip character"},
    {INLCR, "Map NL to CR on input"},
    {IGNCR, "Ignore CR"},
    {ICRNL, "Map CR to NL on input"},
    {IXON, "Enable start/stop output control"},
    //_IXANY, "Enable any char to restart output
    {IXOFF,     "Enable start/stop input control"},
    {0,         NULL}
    };

struct flaginfo local_flags[]={
    ISIG,       "Enable signals",
    ICANON,     "Canonical input(erase and kill)",
    /*_XCASE,   "Canonical upper/lower apperance", */
    ECHO,       "Enable echo",
    ECHOE,      "Echo ERASE as BS-SPACE-BS",
    ECHOK,      "Echo KILL by starting new line",
    0,          NULL
    };


show_baud_rate(int thespeed)
{
    //print the speed in english
    printf("the baud rate is ");
    switch(thespeed){
        case B300:  printf("300\n"); break;
        case B600:  printf("600\n"); break;
        case B1200: printf("1200\n"); break;
        case B1800:  printf("1800\n"); break;
        case B2400: printf("2400\n"); break;
        case B4800: printf("4800\n"); break;
        case B9600: printf("9600\n"); break;
        default: printf("Fast \n"); break;
        }
    }


void show_flagset(int thevalue,struct flaginfo thebitnames[])
{
    //check each bit pattern and display descriptive title

    int i=0;
    for(i=0;thebitnames[i].fl_value;i++){
        printf("%s is ",thebitnames[i].fl_name);
        if(thevalue &thebitnames[i].fl_value)
            printf("ON\n");
        else
            printf("OFF\n");
        }
    }

show_some_flags(struct termios *ttyp)
{
    /* show the values of two of the flag sets_: c_iflag and c_lflag
    add c_oflag and c_cflag is pretty routine ,just add new tales above and a
    bit more code below */
    show_flagset(ttyp->c_iflag,input_flags);
    show_flagset(ttyp->c_lflag,local_flags);
    }

int main(int argc, char *argv[])
{
    struct termios ttyinfo;     //this struct hold tty info
    FILE *fp;

    if((fp = fopen(ctermid(NULL),"r+"))==NULL)
        exit(1);
    if(tcgetattr(fileno(fp),&ttyinfo) == -1){
        perror("Cannot get info about this terminal.");
        exit(1);
        }
    //show info
    show_baud_rate( cfgetospeed(&ttyinfo));     //show baud rate
    printf("\n");
    printf("The erase character is ascii %d,Ctrl- %c\n",ttyinfo.c_cc[VERASE],ttyinfo.c_cc[VERASE]-1+'A');
    printf("\n");
    printf("The line kill character is asii %d,Ctrl- %c\n,ttyinfo.c_cc[VKILL],ttyinfo.c_cc[VKILL]-1+'A');
    show_some_flags(&ttyinfo);
    return 0;
}

4. showtty.c 执行结果。

gcc -o showtty showtty.c
 ./showtty
the baud rate is Fast

The erase character is ascii 127,Ctrl- ?

The line kill character is asii 21,Ctrl- U
Ignore break condition is OFF
Signal interrupt on break is OFF
Ignore chars with parity errors is OFF
Mark parity errors is OFF
Enable input parity check is OFF
Strip character is OFF
Map NL to CR on input is OFF
Ignore CR is OFF
Map CR to NL on input is ON
Enable start/stop output control is ON
Enable start/stop input control is OFF
Enable signals is ON
Canonical input(erase and kill) is ON
Enable echo is ON
Echo ERASE as BS-SPACE-BS is ON
Echo KILL by starting new line is ON