This is my repost. I am a unix newbie trying to learn *nix/C programming.
I can't compile the very first code from Late Stevens apue.  I use freebsd
5.
Plz read the following where I have given all the details
regarding compilation and execution of compiled programme with the errors I
got.
I can't proceed a bit. If I have to halt at the very first code, I simply
don't
know how I will be able to go on. I am sorry to make this post lenthy but I
thought
it might help u to analysis where my fault is or what I have to do .
When I posted first I didn't include codes and error msgs and I
had been advised to give in detail. There are 3 code files in this post,
dirlist.c, error.c & ourhdr.h  I also expect your opinion of whether I
should
learn nix programming or learn c in depth.
--------------------------------------------------------------------------
#include<sys/types.h>
#include<dirent.h>
#include"ourhdr.h"

int
main(int argc, char argv[])
{
DIR *dp;
struct dirent *dirp;
if (argc !=2)
err_quit("a single argment is required");
if ((dp = opendir(argv[1]))== NULL)
err_sys("can't open %s", argv[1]);
while( (dirp=readdir(dp))!=NULL)
printf("%s\n",dirp->d_name);
closedir(dp);
exit(0);
}

----------------------------------------------------------------------------
--
$ gcc dirlist.c
dirlist.c: In function `main':
dirlist.c:12: warning: passing arg 1 of `opendir' makes pointer from integer
without a cast
/var/tmp//ccLw7U6K.o: In function `main':
/var/tmp//ccLw7U6K.o(.text+0x1f): undefined reference to `err_quit'
/var/tmp//ccLw7U6K.o(.text+0x53): undefined reference to `err_sys'
----------------------------------------------------------------------------
---
When I comment out the two error functions like /* err_quit("a single...  */
and /*err_sys(can't open.... */ it is compiled with following warning;
warning: passing arg 1 of `opendir' makes pointer from integer without a
cast.
But when I run it I get the following message;
----------------------------------------------------------------------------
---
$ a.out
Segmentation fault (core dumped).
----------------------------------------------------------------------------
---
At this point I try to open the "a.out.core" file with text editor.
Only one word, "ELF" is there.
Again I tried to compile it with another file, error.c(following file);
----------------------------------------------------------------------------
---
#include<errno.h>  /* for definition of errno */
#include<stdarg.h>  /* ANSI C header file */
#include"ourhdr.h"

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

char *pname = NULL;  /* caller can set this from argv[0] */

/* 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, fmt, ap);
va_end(ap);
return;
}

/* 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, 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, 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, fmt, ap);
va_end(ap);
return;
}

/* 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, fmt, ap);
va_end(ap);
exit(1);
}

/* Print a message and return to caller.
* Caller specifies "errnoflag". */

static void
err_doit(int errnoflag, const char *fmt, va_list ap)
{
int errno_save;
char buf[MAXLINE];

errno_save = errno;  /* value caller might want printed */
vsprintf(buf, fmt, ap);
if (errnoflag)
sprintf(buf+strlen(buf), ": %s", strerror(errno_save));
strcat(buf, "\n");
fflush(stdout);  /* in case stdout and stderr are the same */
fputs(buf, stderr);
fflush(NULL);  /* flushes all stdio output streams */
return;
}
----------------------------------------------------------------------------
-------
$ gcc dirlist.c error.c and I got the file compiled with warning;
---------------------------------------------------------------------
dirlist.c: In function `main':
dirlist.c:12: warning: passing arg 1 of `opendir' makes pointer from integer
without a cast
----------------------------------------------------------------------------
------
When I tried to run the file with argument like;
-----------------------
$ a.out guess.c
Bus error (core dumped)
--------------------------
This core file contains the same word "elf".  ourhdr.h is follows;
---------------------------------------------------
/* Our own header, to be included *after* all standard system headers */

#ifndef __ourhdr_h
#define __ourhdr_h

#include <sys/types.h> /* required for some of our prototypes */
#include <stdio.h> /* for convenience */
#include <stdlib.h> /* for convenience */
#include <string.h> /* for convenience */
#include <unistd.h> /* for convenience */

#define MAXLINE 4096 /* max line length */

#define FILE_MODE (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)
/* default file access permissions for new files */
#define DIR_MODE (FILE_MODE | S_IXUSR | S_IXGRP | S_IXOTH)
/* default permissions for new directories */

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

/* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
#if defined(SIG_IGN) && !defined(SIG_ERR)
#define SIG_ERR ((Sigfunc *)-1)
#endif

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

/* prototypes for our own functions */
char *path_alloc(int *);   /* {Prog pathalloc} */
int  open_max(void);   /* {Prog openmax} */
void clr_fl(int, int);   /* {Prog setfl} */
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} */

int tty_cbreak(int);   /* {Prog raw} */
int tty_raw(int);    /* {Prog raw} */
int tty_reset(int);   /* {Prog raw} */
void tty_atexit(void);   /* {Prog raw} */
#ifdef ECHO /* only if <termios.h> has been included */
struct termios *tty_termios(void); /* {Prog raw} */
#endif

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

int s_pipe(int *);    /* {Progs svr4_spipe bsd_spipe} */
int recv_fd(int, ssize_t (*func)(int, const void *, size_t));
/* {Progs recvfd_svr4 recvfd_43bsd} */
int send_fd(int, int);   /* {Progs sendfd_svr4 sendfd_43bsd} */
int send_err(int, int, const char *);/* {Prog senderr} */
int serv_listen(const char *); /* {Progs servlisten_svr4 servlisten_44bsd}
*/
int serv_accept(int, uid_t *); /* {Progs servaccept_svr4 servaccept_44bsd}
*/
int cli_conn(const char *); /* {Progs cliconn_svr4 cliconn_44bsd} */
int buf_args(char *, int (*func)(int, char **));/* {Prog bufargs} */


int ptym_open(char *);   /* {Progs ptyopen_svr4 ptyopen_44bsd} */
int ptys_open(int, char *); /* {Progs ptyopen_svr4 ptyopen_44bsd} */
#ifdef TIOCGWINSZ
pid_t pty_fork(int *, char *, 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_readlock(fd, offset, whence, len) \
lock_test(fd, F_RDLCK, offset, whence, len)
#define is_writelock(fd, offset, whence, len) \
lock_test(fd, F_WRLCK, offset, whence, len)

void err_dump(const char *, ...); /* {App misc_source} */
void err_msg(const char *, ...);
void err_quit(const char *, ...);
void err_ret(const char *, ...);
void err_sys(const char *, ...);
void log_msg(const char *, ...);  /* {App misc_source} */
void log_open(const char *, int, int);
void log_quit(const char *, ...);
void log_ret(const char *, ...);
void log_sys(const char *, ...);
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 /* __ourhdr_h */

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