Troubleshooting Compilation Errors for 《Advanced Programming in the UNIX Environment》(APUE2) Source Code on Linux

Introduction

I believe many friends, like me, who are eager to learn Unix programming, might have been disheartened when they excitedly got their hands on 《Advanced Programming in the UNIX Environment》, only to encounter a slew of errors when trying to compile the first example, myls. Today, I'm writing down the solutions, partly for my own record, and partly to help others who are struggling with the same issues to quickly enter the wonderful world of Linux. (Linux systems only)

Troubleshooting Compilation Errors

The compilation errors in the APUE2 source code can be resolved by following these steps:

First, you need to make the source code once.
Edit Make.defines.linux located in the apue.2e folder, which is generated after extracting the source code.
Change WKDIR=/home/var/apue.2e to your apue.2e directory. For example, if my APUE source code is extracted to /usr/local/apue.2e, I would change it to WKDIR=/usr/local/apue.2e.
Then, enter the apue.2e/std directory and edit linux.mk. Replace all instances of nawk with awk.
Finally, return to the apue.2e directory and execute the make command.

Error 1: `apue.h` Not Found

If you encounter the following error:

myls.c:1:19: apue.h: No such file or directory

myls.c: In function ‘main’:

myls.c:13: error: ‘NULL’ undeclared (first use in this function)

myls.c:13: error: (Each undeclared identifier is reported only once

myls.c:13: error: for each function it appears in.)

The solution is to copy apue.h to the system's default header file directory:

$cp /usr/local/apue.2e/include/apue.h /usr/include

Error 2: Undefined Reference to `err_quit` and `err_sys`

If you encounter the following error:

/tmp/ccBBopm0.o(.text+0x2b): In function ‘main’:

: undefined reference to ‘err_quit’

/tmp/ccBBopm0.o(.text+0x5f): In function ‘main’:

: undefined reference to ‘err_sys’

collect2: ld returned 1 exit status

The solution is to create a new header file myerr.h in the /usr/include directory and copy the contents of the original apue.h file into it.

Understanding the Compilation Process

The APUE2 source code compilation process can be complex, but understanding the basics can help you troubleshoot issues. Here are some key points to note:

The make command is used to build the source code.
The Make.defines.linux file contains system-specific settings, including the WKDIR variable, which specifies the location of the apue.2e directory.
The linux.mk file contains Makefile rules for building the source code.
The apue.h header file contains definitions for the APUE2 library.
The err_quit and err_sys functions are used for error handling.

Compiling Individual Source Files

If you want to compile individual source files, you can follow these steps:

First, make sure you have the libapue.a library file in the lib directory.
Then, modify the apue.h header file to include the correct path to the apue.h file.
Finally, compile the source file using the gcc command, including the libapue.a library file.

For example, to compile the fig1.3 source file, you would use the following command:

$gcc fig1.3.c lib/libapue.a

This will generate a executable file called a.out. You can then run the executable file using the following command:

$./a.out /home

This will list the files and directories in the /home directory.

Conclusion

Troubleshooting compilation errors in the APUE2 source code can be challenging, but by following the steps outlined in this article, you should be able to resolve common issues. Remember to always check the Make.defines.linux file and the linux.mk file for system-specific settings, and to include the correct path to the apue.h header file when compiling individual source files.