为什么80%的码农都做不了架构师？>>> 
1.autoscan (autoconf): 扫描源代码以搜寻普通的可移植性问题，比如检查编译器，库，头文件等，生成文件configure.scan,它是configure.ac的一个雏形。
your source files --> [autoscan*] --> [configure.scan] --> configure.ac
2.aclocal (automake):根据已经安装的宏，用户定义宏和acinclude.m4文件中的宏将configure.ac文件所需要的宏集中定义到文件 aclocal.m4中。aclocal是一个perl 脚本程序，它的定义是：“aclocal - create aclocal.m4 by scanning configure.ac”user input files optional input process output files
================ ============== ======= ============acinclude.m4 - - - - -.V.-------,
configure.ac ------------------------>|aclocal|{user macro files} ->| |------> aclocal.m4`-------'
3.autoheader(autoconf): 根据configure.ac中的某些宏，比如cpp宏定义，运行m4，声称config.h.inuser input files optional input process output files
================ ============== ======= ============aclocal.m4 - - - - - - - .|V.----------,
configure.ac ----------------------->|autoheader|----> autoconfig.h.in`----------'4.automake: automake将Makefile.am中定义的结构建立Makefile.in，然后configure脚本将生成的Makefile.in文件转换 为Makefile。如果在configure.ac中定义了一些特殊的宏，比如AC_PROG_LIBTOOL，它会调用libtoolize，否则它 会自己产生config.guess和config.sub
user input files optional input processes output files
================ ============== ========= ============.--------,| | - - -> COPYING| | - - -> INSTALL| |------> install-sh| |------> missing|automake|------> mkinstalldirs
configure.ac ----------------------->| |
Makefile.am ----------------------->| |------> Makefile.in| |------> stamp-h.in.---+ | - - -> config.guess| | | - - -> config.sub| `------+-'| | - - - -> config.guess|libtoolize| - - - -> config.sub| |--------> ltmain.sh| |--------> ltconfig`----------'5.autoconf:将configure.ac中的宏展开，生成configure脚本。这个过程可能要用到aclocal.m4中定义的宏。
user input files optional input processes output files
================ ============== ========= ============aclocal.m4 ,autoconfig.h.in - - - - - - -.V.--------,
configure.ac ----------------------->|autoconf|------> configure6. ./configure的过程.-------------> [config.cache]configure* --------------------------+-------------> config.log|[config.h.in] -. v .--> [autoconfig.h]+-------> config.status* -+ Makefile.in ---' `--> Makefile7. make过程[autoconfig.h] -.+--> make* ---> 程序Makefile ---'.---------,config.site - - ->| |config.cache - - ->|configure| - - -> config.cache| +-,`-+-------' || |----> config.statusconfig.h.in ------->|config- |----> config.hMakefile.in ------->| .status|----> Makefile| |----> stamp-h| +--,.-+ | || `------+--' |ltmain.sh ------->|ltconfig|-------> libtool| | |`-+------' ||config.guess|| config.sub |`------------'
.--------,Makefile ------>| |config.h ------>| make |
{project sources} ---------------->| |--------> {project targets}.-+ +--,| `--------' || libtool || missing || install-sh ||mkinstalldirs|`-------------'在/hello/目录下创建一个hello.c文件，并编译运行它：
#cd /hello/
(1) 编写源文件hello.c：
#include<stdio.h>
int main(int argc, char** argv)
{
printf("Hello, GNU!n");
return 0;
}
[litao@vm0000131 hello]$ ll
total 4
-rw-rw-r-- 1 litao litao 68 Aug 12 12:02 hello.c
一、autoscan
[litao@vm0000131 hello]$ autoscan
autom4te: configure.ac: no such file or directory
autoscan: /usr/bin/autom4te failed with exit status: 1
[litao@vm0000131 hello]$ ll
total 8
-rw-rw-r-- 1 litao litao 0 Aug 12 12:03 autoscan.log
-rw-rw-r-- 1 litao litao 457 Aug 12 12:03 configure.scan
-rw-rw-r-- 1 litao litao 68 Aug 12 12:02 hello.c
已经生成了configure.scan，autoscan.log文件
将configure.scan 修改为 configure.in，最后修改的内容如下：
[litao@vm0000131 hello]$ mv configure.scan configure.in
[litao@vm0000131 hello]$ vim configure.in
# -*- Autoconf -*-
# Process this file with autoconf to produce a configure script.
AC_PREREQ(2.59)
AC_INIT(FULL-PACKAGE-NAME, VERSION, BUG-REPORT-ADDRESS)
AC_CONFIG_SRCDIR([hello.c])
#AC_CONFIG_HEADER([config.h])
AM_INIT_AUTOMAKE(hello, 1.0)
# Checks for programs.
AC_PROG_CC
# Checks for libraries.
# Checks for header files.
# Checks for typedefs, structures, and compiler characteristics.
# Checks for library functions.
AC_OUTPUT(Makefile)
二、acloacl
[litao@vm0000131 hello]$ aclocal
生成 aclocal.m4 和 autom4te.cache (生成aclocal.m4的过程中涉及到configure.in)
[litao@vm0000131 hello]$ ll
total 44
-rw-rw-r-- 1 litao litao 31120 Aug 12 12:08 aclocal.m4
drwxr-xr-x 2 litao litao 4096 Aug 12 12:08 autom4te.cache
-rw-rw-r-- 1 litao litao 0 Aug 12 12:03 autoscan.log
-rw-rw-r-- 1 litao litao 496 Aug 12 12:08 configure.in
-rw-rw-r-- 1 litao litao 68 Aug 12 12:02 hello.c
三、antoconf
生成 configure (根据 configure.in, 和 aclocal.m4)
[litao@vm0000131 hello]$ ll
total 168
-rw-rw-r-- 1 litao litao 31120 Aug 12 12:08 aclocal.m4
drwxr-xr-x 2 litao litao 4096 Aug 12 12:11 autom4te.cache
-rw-rw-r-- 1 litao litao 0 Aug 12 12:03 autoscan.log
-rwxrwxr-x 1 litao litao 122297 Aug 12 12:11 configure
-rw-rw-r-- 1 litao litao 496 Aug 12 12:08 configure.in
-rw-rw-r-- 1 litao litao 68 Aug 12 12:02 hello.c
四、编写Makefile.am：
AUTOMAKE_OPTIONS= foreign
bin_PROGRAMS= hello
hello_SOURCES= hello.c
生成 Makefile.in， depcomp， install-sh， 和 missing (根据 Makefile.am, 和 aclocal.m4)
[litao@vm0000131 hello]$ automake
configure.in: required file `./install-sh' not found
configure.in: required file `./missing' not found
Makefile.am: required file `./depcomp' not found
[litao@vm0000131 hello]$ automake --add-missing
configure.in: installing `./install-sh'
configure.in: installing `./missing'
Makefile.am: installing `./depcomp'
[litao@vm0000131 hello]$ ll
total 192
-rw-rw-r-- 1 litao litao 31120 Aug 12 12:08 aclocal.m4
drwxr-xr-x 2 litao litao 4096 Aug 12 12:14 autom4te.cache
-rw-rw-r-- 1 litao litao 0 Aug 12 12:03 autoscan.log
-rwxrwxr-x 1 litao litao 122297 Aug 12 12:11 configure
-rw-rw-r-- 1 litao litao 496 Aug 12 12:08 configure.in
lrwxrwxrwx 1 litao litao 31 Aug 12 12:16 depcomp -> /usr/share/automake-1.9/depcomp
-rw-rw-r-- 1 litao litao 68 Aug 12 12:02 hello.c
lrwxrwxrwx 1 litao litao 34 Aug 12 12:16 install-sh -> /usr/share/automake-1.9/install-sh
-rw-rw-r-- 1 litao litao 69 Aug 12 12:15 Makefile.am
-rw-rw-r-- 1 litao litao 16561 Aug 12 12:16 Makefile.in
lrwxrwxrwx 1 litao litao 31 Aug 12 12:16 missing -> /usr/share/automake-1.9/missing
六、configure
生成 Makefile， config.log， 和 config.status
