#include <sys/wait.h>

#include <signal.h>

#include <errno.h>

#include <unistd.h>

#include <sys/stat.h>

#include <sys/types.h>

#ifndef MAX_PARAM

#define MAX_PARAM 10

#endif

/*

 * start child process

 */

int new_process(char * const cmd_line[MAX_PARAM])

{

	int proc_status;

	pid_t pid;

	pid_t w;

	struct stat file_status;

	/* memory for storage of function pointers from the signal handling routines */

	void (*int_stat)();

	void (*quit_stat)();

	void (*usr2_stat)();

	/*

	 * check command file

	 */

	/* search file */

	if (stat(cmd_line[0], &file_status) < 0) {

		fprintf(stderr, "Cannot find program '%s'.\n", cmd_line[0]);

		fprintf(stderr, "You must specify path for '%s'.\n", cmd_line[0]);

		return -errno;

	}

	proc_status = 0;

	/* check file status and permissions */

	if (file_status.st_mode & S_IFREG) {

		if (!(file_status.st_mode & S_IXOTH)) {

			if (!(file_status.st_mode & S_IXGRP)) {

				if (!(file_status.st_mode & S_IXUSR)) {

					proc_status = -EACCES;

				} else if (file_status.st_uid != getuid()) {

					proc_status = -EACCES;

				}

			} else if ((file_status.st_gid != getgid()) && (file_status.st_uid != getuid())) {

				proc_status = -EACCES;

			}

		}

	} else {

		proc_status = -EACCES;

	}

	if (proc_status != 0) {

		fprintf(stderr, "No permissions to execute program '%s'.\n", cmd_line[0]);

		return proc_status;

	}

	if ( (pid = fork() ) == 0) {

		execv(cmd_line[0], cmd_line);

	}

	/* for waiting ingnoring special interrupts */

	int_stat = signal(SIGINT, SIG_IGN);

	quit_stat = signal(SIGQUIT, SIG_IGN);

	usr2_stat = signal(SIGUSR2, SIG_IGN);

	/* waiting for the end of the child process */

	while ( ( (w = wait(&proc_status)) != pid ) && (w != -1) )

		;

	if (w == -1) {

		proc_status = -errno;

	}

	/* restore pointers from signal handling routines */

	signal(SIGINT, int_stat);

	signal(SIGQUIT, quit_stat);

	signal(SIGUSR2, usr2_stat);

	return proc_status;

}