ans  =
 
    1.  
 
-->exec('Example15.sci')
 
-->clear
 
-->flag=1
 flag  =
 
    1.  
 
-->mode(-1)
Current date is 23-Jun-2013 
 
Welcome to the Textbook Companionship Project 2013 
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 Book Title                             :       UNIX CONCEPTS AND APPLICATIONS    
 
 Book Edition                         :                                                                           4   
 
 Book Author                          :                                                    Sumitabha Das   
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 Code Author                          :                                                     Pranav Bhat T   
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 Chapter Number                    :                                                                            24   
 
 Chapter Title                         :                              Systems programming II- Files   
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Example 15    :       Show the effect of [Ctrl-c] in the shell so as to do some operations 
 
 ****************************************************************   
 
 Answer    :      
 
 INSTRUCTIONS   :    
  
 1.These programs are part of systems programming PURELY in Unix and the commands have NO EQUIVALENT IN SCILAB   
  
 2.However the .c files which are displayed here are also made into a seperate file.If you are a unix user then try compiling and 
       running the programme with gcc or cc compiler                                                                              
  
 3.The outputs displayed here are just MOCK OUTPUTS which are DISPLAYED IN THE TEXTBOOK   
  
 4.The inconvenience is regretted.   
.............Press [ENTER] to continue.....	UNIX SHELL SIMULATOR(DEMO VERSION WITH PRELOADED COMMANDS)




$ cat signal2.c      # to open the file emp.lst /* Program: signal2.c -- Handles SIGINT and SIGTSTP generated from terminal Required two [Ctrl-c]s to terminate */'
#include <stdio.h>
#include <unistd.h>
#include <signal.h>

void quit(char *message, int exit_status) ;
void tstp_handler(int signo);    /* Handler for [Ctrl-z] */
void int_handler(int signo);     /* Handler for [Ctrl-c] */
int n, count=0;

int main(void) {
    signal(SIGTSTP, tstp_handler); /* Disposition for these two signals */
    signal(SIGINT, int_handler);   /* set to enter respective handler */
    signal(SIGQUIT, SIG_IGN);      /* Disposition set to ignore */
    
    fprintf(stderr,"Press [Ctrl-z] first, then [Ctrl-c]\n");
    for(;;)
     pause();                  /* Will return on reciept of help */
}

void tstp_handler(int signo) {
     signal(SIGTSTP, tstp_handler);        /* Not entirely reliable */
     fprintf(stderr, "Can't stop this program\n");  /* same signal can reset */
}                                          /* disposition to default */

void int_handler(int signo) {             /* Will terminate program */
       signal(SIGINT, int_handler);        /* on second invocation */
       (++count == 1) ? printf("Press again\n") : quit("Quitting", 1);
 $ cc signal2.c $ a.out  Press [Ctrl-z] first, then [Ctrl-c]# [Ctrl - \] pressed                                       Signal Ignored  
# [Ctrl - z] pressed                 
Cannot stop this program                 From tstp_handler
# [Ctrl - c] pressed                 
Press again                     From int_handler
# [Ctrl - c] pressed                 
Quitting: Interrupted system call           From int_handler 


$ exit        #To exit the current simulation terminal and return to Scilab console

........# (hit [ENTER] for result)

			BACK TO SCILAB CONSOLE...
Loading initial environment 
-->diary(0)