COMS 4995 Advanced Systems Programming

Index of 2024-9/code/04

Parent directory
Makefile
apue.h
error.c
shell1.c

Makefile

CC=gcc
CFLAGS=-g -Wall

shell1: error.o

.PHONY: clean
clean:
	rm -f shell1 *.o
	rm -rf *.dSYM

.PHONY: all
all: clean shell1

apue.h

/*
 * Our own header, to be included before all standard system headers.
 */
#ifndef	_APUE_H
#define	_APUE_H

#define _POSIX_C_SOURCE 200809L

#if defined(SOLARIS)		/* Solaris 10 */
#define _XOPEN_SOURCE 600
#else
#define _XOPEN_SOURCE 700
#endif

#include <sys/types.h>		/* some systems still require this */
#include <sys/stat.h>
#include <sys/termios.h>	/* for winsize */
#if defined(MACOS) || !defined(TIOCGWINSZ)
#include <sys/ioctl.h>
#endif

#include <stdio.h>		/* for convenience */
#include <stdlib.h>		/* for convenience */
#include <stddef.h>		/* for offsetof */
#include <string.h>		/* for convenience */
#include <unistd.h>		/* for convenience */
#include <signal.h>		/* for SIG_ERR */

#define	MAXLINE	4096			/* max line length */

/*
 * Default file access permissions for new files.
 */
#define	FILE_MODE	(S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)

/*
 * Default permissions for new directories.
 */
#define	DIR_MODE	(FILE_MODE | S_IXUSR | S_IXGRP | S_IXOTH)

typedef	void	Sigfunc(int);	/* for signal handlers */

#define	min(a,b)	((a) < (b) ? (a) : (b))
#define	max(a,b)	((a) > (b) ? (a) : (b))

/*
 * Prototypes for our own functions.
 */
char	*path_alloc(size_t *);				/* {Prog pathalloc} */
long	 open_max(void);					/* {Prog openmax} */

int		 set_cloexec(int);					/* {Prog setfd} */
void	 clr_fl(int, int);
void	 set_fl(int, int);					/* {Prog setfl} */

void	 pr_exit(int);						/* {Prog prexit} */

void	 pr_mask(const char *);				/* {Prog prmask} */
Sigfunc	*signal_intr(int, Sigfunc *);		/* {Prog signal_intr_function} */

void	 daemonize(const char *);			/* {Prog daemoninit} */

void	 sleep_us(unsigned int);			/* {Ex sleepus} */
ssize_t	 readn(int, void *, size_t);		/* {Prog readn_writen} */
ssize_t	 writen(int, const void *, size_t);	/* {Prog readn_writen} */

int		 fd_pipe(int *);					/* {Prog sock_fdpipe} */
int		 recv_fd(int, ssize_t (*func)(int,
		         const void *, size_t));	/* {Prog recvfd_sockets} */
int		 send_fd(int, int);					/* {Prog sendfd_sockets} */
int		 send_err(int, int,
		          const char *);			/* {Prog senderr} */
int		 serv_listen(const char *);			/* {Prog servlisten_sockets} */
int		 serv_accept(int, uid_t *);			/* {Prog servaccept_sockets} */
int		 cli_conn(const char *);			/* {Prog cliconn_sockets} */
int		 buf_args(char *, int (*func)(int,
		          char **));				/* {Prog bufargs} */

int		 tty_cbreak(int);					/* {Prog raw} */
int		 tty_raw(int);						/* {Prog raw} */
int		 tty_reset(int);					/* {Prog raw} */
void	 tty_atexit(void);					/* {Prog raw} */
struct termios	*tty_termios(void);			/* {Prog raw} */

int		 ptym_open(char *, int);			/* {Prog ptyopen} */
int		 ptys_open(char *);					/* {Prog ptyopen} */
#ifdef	TIOCGWINSZ
pid_t	 pty_fork(int *, char *, int, const struct termios *,
		          const struct winsize *);	/* {Prog ptyfork} */
#endif

int		lock_reg(int, int, int, off_t, int, off_t); /* {Prog lockreg} */

#define	read_lock(fd, offset, whence, len) \
			lock_reg((fd), F_SETLK, F_RDLCK, (offset), (whence), (len))
#define	readw_lock(fd, offset, whence, len) \
			lock_reg((fd), F_SETLKW, F_RDLCK, (offset), (whence), (len))
#define	write_lock(fd, offset, whence, len) \
			lock_reg((fd), F_SETLK, F_WRLCK, (offset), (whence), (len))
#define	writew_lock(fd, offset, whence, len) \
			lock_reg((fd), F_SETLKW, F_WRLCK, (offset), (whence), (len))
#define	un_lock(fd, offset, whence, len) \
			lock_reg((fd), F_SETLK, F_UNLCK, (offset), (whence), (len))

pid_t	lock_test(int, int, off_t, int, off_t);		/* {Prog locktest} */

#define	is_read_lockable(fd, offset, whence, len) \
			(lock_test((fd), F_RDLCK, (offset), (whence), (len)) == 0)
#define	is_write_lockable(fd, offset, whence, len) \
			(lock_test((fd), F_WRLCK, (offset), (whence), (len)) == 0)

void	err_msg(const char *, ...);			/* {App misc_source} */
void	err_dump(const char *, ...) __attribute__((noreturn));
void	err_quit(const char *, ...) __attribute__((noreturn));
void	err_cont(int, const char *, ...);
void	err_exit(int, const char *, ...) __attribute__((noreturn));
void	err_ret(const char *, ...);
void	err_sys(const char *, ...) __attribute__((noreturn));

void	log_msg(const char *, ...);			/* {App misc_source} */
void	log_open(const char *, int, int);
void	log_quit(const char *, ...) __attribute__((noreturn));
void	log_ret(const char *, ...);
void	log_sys(const char *, ...) __attribute__((noreturn));
void	log_exit(int, const char *, ...) __attribute__((noreturn));

void	TELL_WAIT(void);		/* parent/child from {Sec race_conditions} */
void	TELL_PARENT(pid_t);
void	TELL_CHILD(pid_t);
void	WAIT_PARENT(void);
void	WAIT_CHILD(void);

#endif	/* _APUE_H */

error.c

#include "apue.h"
#include <errno.h>		/* for definition of errno */
#include <stdarg.h>		/* ISO C variable aruments */

static void	err_doit(int, int, const char *, va_list);

/*
 * Nonfatal error related to a system call.
 * Print a message and return.
 */
void
err_ret(const char *fmt, ...)
{
	va_list		ap;

	va_start(ap, fmt);
	err_doit(1, errno, fmt, ap);
	va_end(ap);
}

/*
 * Fatal error related to a system call.
 * Print a message and terminate.
 */
void
err_sys(const char *fmt, ...)
{
	va_list		ap;

	va_start(ap, fmt);
	err_doit(1, errno, fmt, ap);
	va_end(ap);
	exit(1);
}

/*
 * Nonfatal error unrelated to a system call.
 * Error code passed as explict parameter.
 * Print a message and return.
 */
void
err_cont(int error, const char *fmt, ...)
{
	va_list		ap;

	va_start(ap, fmt);
	err_doit(1, error, fmt, ap);
	va_end(ap);
}

/*
 * Fatal error unrelated to a system call.
 * Error code passed as explict parameter.
 * Print a message and terminate.
 */
void
err_exit(int error, const char *fmt, ...)
{
	va_list		ap;

	va_start(ap, fmt);
	err_doit(1, error, fmt, ap);
	va_end(ap);
	exit(1);
}

/*
 * Fatal error related to a system call.
 * Print a message, dump core, and terminate.
 */
void
err_dump(const char *fmt, ...)
{
	va_list		ap;

	va_start(ap, fmt);
	err_doit(1, errno, fmt, ap);
	va_end(ap);
	abort();		/* dump core and terminate */
	exit(1);		/* shouldn't get here */
}

/*
 * Nonfatal error unrelated to a system call.
 * Print a message and return.
 */
void
err_msg(const char *fmt, ...)
{
	va_list		ap;

	va_start(ap, fmt);
	err_doit(0, 0, fmt, ap);
	va_end(ap);
}

/*
 * Fatal error unrelated to a system call.
 * Print a message and terminate.
 */
void
err_quit(const char *fmt, ...)
{
	va_list		ap;

	va_start(ap, fmt);
	err_doit(0, 0, fmt, ap);
	va_end(ap);
	exit(1);
}

/*
 * Print a message and return to caller.
 * Caller specifies "errnoflag".
 */
static void
err_doit(int errnoflag, int error, const char *fmt, va_list ap)
{
	char	buf[MAXLINE];

	vsnprintf(buf, MAXLINE-1, fmt, ap);
	if (errnoflag)
		snprintf(buf+strlen(buf), MAXLINE-strlen(buf)-1, ": %s",
		  strerror(error));
	strcat(buf, "\n");
	fflush(stdout);		/* in case stdout and stderr are the same */
	fputs(buf, stderr);
	fflush(NULL);		/* flushes all stdio output streams */
}

shell1.c

#include "apue.h"
#include <sys/wait.h>

int
main(void)
{
	char	buf[MAXLINE];	/* from apue.h */
	pid_t	pid;
	int		status;

	printf("%% ");	/* print prompt (printf requires %% to print %) */
	while (fgets(buf, MAXLINE, stdin) != NULL) {
		if (buf[strlen(buf) - 1] == '\n')
			buf[strlen(buf) - 1] = 0; /* replace newline with null */

		if ((pid = fork()) < 0) {
			err_sys("fork error");
		} else if (pid == 0) {		/* child */
			execlp(buf, buf, (char *)0);
			err_ret("couldn't execute: %s", buf);
			exit(127);
		}

		/* parent */
		if ((pid = waitpid(pid, &status, 0)) < 0)
			err_sys("waitpid error");
		printf("%% ");
	}
	exit(0);
}