开始学习《Unix网络编程》，输入第一个程序后，遇到各种错误，先将解决方案记录如下。
遇到的第一个错误是：没有找到头文件“unp.h”,该头文件是作者自己写的，并不包含在／usr／include中，这时需要到网上下载unpv13e.tar.gz到某一目录。具体操作：
mkdir /home/yourname/download ％创建存放压缩文件的目录
tar -xzvf unpv13e.tar.gz ％解压
ls -al ％查看该目录下的文件
cd unpv13e ％进入unpv13e
cat README %查看README文件，其中有具体的安装信息，按照操作即可
QUICK AND DIRTY
===============
Execute the following from the src/ directory:
./configure # try to figure out all implementation differences
cd lib # build the basic library that all programs need
make # use "gmake" everywhere on BSD/OS systems
cd ../libfree # continue building the basic library
make
cd ../libroute # only if your system supports 4.4BSD style routing sockets
make # only if your system supports 4.4BSD style routing sockets
cd ../libxti # only if your system supports XTI
make # only if your system supports XTI
cd ../intro # build and test a basic client program
make daytimetcpcli
./daytimetcpcli 127.0.0.1
If all that works, you're all set to start compiling individual programs.
然后，复制unp.h和config.h到/usr/include
cp libunp.a /usr/lib
cp libunp.a /usr/lib64/
cd /lib
cp unp.h /usr/include
cp config.h /usr/include
最后，修改unp.h中的#include "../config.h"为#include "./config.h"。
以上是第一个错误，下面的错误是：
undefined reference to 'err_quit'
undefined reference to 'err_sys'
这也是由于，意思是未定义的声明，也就是说这些函数没有实现，这时候在网上找的自定义错误处理函数myerr.h
#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);
}
/*
* 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, fmt, ap);
if (errnoflag)
snprintf(buf+strlen(buf), MAXLINE-strlen(buf), ": %s",
strerror(error));
strcat(buf, " ");
fflush(stdout); /* in case stdout and stderr are the same */
fputs(buf, stderr);
fflush(NULL); /* flushes all stdio output streams */
}