/* execute.c - code used by small shell to execute commands */#include	<stdio.h>#include	<stdlib.h>#include	<unistd.h>#include	<signal.h>#include	<sys/wait.h>int execute(char *argv[])/* * purpose: run a program passing it arguments * returns: status returned via wait, or -1 on error *  errors: -1 on fork() or wait() errors */{	int	pid ;	int	child_info = -1;	if ( argv[0] == NULL )		/* nothing succeeds	*/		return 0;	if ( (pid = fork())  == -1 )		perror("fork");	else if ( pid == 0 ){		signal(SIGINT, SIG_DFL);		signal(SIGQUIT, SIG_DFL);		execvp(argv[0], argv);		perror("cannot execute command");		exit(1);	}	else {		if ( wait(&child_info) == -1 )			perror("wait");	}	return child_info;}