Catch < Ctrl + C > on Linux ==> can not run execvp

[thanhnh]

Hi. I have to write a simple Shell with History feature. First, I get a string from command line. The command line is split into tokens. And then, I call fork ( ) to create a new process. The child process will call execvp(args[0], args) in order to execute the string command line. When user press < Ctrl + C > ( signal SIGINT ) , I have to read a file and print out 10 last commands.

My problem is: when I embed small code to catch < Ctrl + C > into my program as bold text below, I can not run execvp( ). The error is : bad address !!!

#include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>

#define BUFFER_SIZE 50

static char buffer[BUFFER_SIZE];

void handle_SIGINT(int sig_num ){
write(STDOUT_FILENO, buffer, strlen(buffer));
exit(0);
}

int main(){

/*
struct sigaction handler;
handler.sa_handler = handle_SIGINT; //* <=== ERROR */
handler.sa_flags = 0;
sigemptyset(&handler.sa_mask);
sigaction(SIGINT, &handler, NULL);
strcpy(buffer, "Caught <Ctrl> <c>\n");

*/
char inputBuffer[MAX_LINE]; /*buffer to hold the command entired */
char* args[MAX_LINE/ +1]; /*command line ( of 80 ) has max of 40 argument */
int background; /*equals 1 if a command is folowed by '&' */
setup(inputBuffer, args , &background); /*setup the command line */

pid_t pid;
pid = fork();

switch(pid):
case -1:
//fork() error.

case 0:
// call execvp(args[0], args) to run shell commands
default:
//.................
return(0);
}

How can I fix this prolem ? Help me, please !!!

[horace1]

The code would not compile initially so I fixed a couple of problems, indicated by // ** comments

include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
 
#define BUFFER_SIZE 50   //  ** added
#define MAX_LINE 100
 
static char buffer[BUFFER_SIZE];
 
void handle_SIGINT(int sig_num ){
write(STDOUT_FILENO, buffer, strlen(buffer));
exit(0);
}
 
int main(){
 
 
struct sigaction handler;
handler.sa_handler = handle_SIGINT; //* <=== ERROR */
handler.sa_flags = 0;
sigemptyset(&handler.sa_mask);
sigaction(SIGINT, &handler, NULL);
strcpy(buffer, "Caught <Ctrl> <c>\n");
 
 
char inputBuffer[MAX_LINE]; /*buffer to hold the command entired */
char* args[MAX_LINE/ +1]; /*command line ( of 80 ) has max of 40 argument */
int background; /*equals 1 if a command is folowed by '&' */
//setup(inputBuffer, args , &background); /*setup the command line */
 
pid_t pid;
pid = fork();
 
switch(pid){                 //  *** changed : to {
case -1:
//fork() error.
 
case 0:
// call execvp(args[0], args) to run shell commands
default:;
}                // ** added }
//.................
printf("Done");
while(1);        // added
return(0);        // added
}
 

it compiles and when run forks() a child proceess and the parent and child loop at the while(1); statement.
when I hit <CTRL/C> it is caught and both processes print "Caught <Ctrl> <c>" then "Done" then stop. e.g. a run gave

$sig
Caught <Ctrl> <c>
DoneCaught <Ctrl> <c>
Done
$
 

[thanhnh]

Oh, many thanks to you. Wish a best health 4 you :)