gem安装软件时遇到的问题以及解决思路

今天需要在由于工作需要，需要使用bundle install来更新依赖包，本以为很顺利，结果遇到了下面的一堆问题，在此进行记录并分享自己遇到这个问题时的思路：

问题一：用gem安装ruby的包时出错

root@kali:~/Desktop# gem install nokogiri -v '1.6.8.1'

Building native extensions. This could take a while...
ERROR: Error installing nokogiri:
ERROR: Failed to build gem native extension.

current directory: /var/lib/gems/2.3.0/gems/nokogiri-1.6.8.1/ext/nokogiri
/usr/bin/ruby2.3 -r ./siteconf20171027-10596-epcpmc.rb extconf.rb
checking if the C compiler accepts ... yes
Building nokogiri using packaged libraries.
Using mini_portile version 2.1.0
checking for gzdopen() in -lz... no
zlib is missing; necessary for building libxml2
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary libraries and/or
headers. Check the mkmf.log file for more details. You may need configuration options.

Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/usr/bin/$(RUBY_BASE_NAME)2.3
--help
--clean
--use-system-libraries
--enable-static
--disable-static
--with-zlib-dir
--without-zlib-dir
--with-zlib-include
--without-zlib-include=${zlib-dir}/include
--with-zlib-lib
--without-zlib-lib=${zlib-dir}/lib
--enable-cross-build
--disable-cross-build

To see why this extension failed to compile, please check the mkmf.log which can be found
here:

/var/lib/gems/2.3.0/extensions/x86_64-linux/2.3.0/nokogiri-1.6.8.1/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in /var/lib/gems/2.3.0/gems/nokogiri-1.6.8.1 for inspection.
Results logged to /var/lib/gems/2.3.0/extensions/x86_64-linux/2.3.0/nokogiri-1.6.8.1/gem_make.out

问题描述：

gem开始尝试安装，然后依次出现以下错误：
1.安装nokogiri失败；
2.构建gem本地拓展失败；

然后，gem开始检查为什么失败：
1.checking if the C compiler accepts ... yes
2.checking for gzdopen() in -lz... no

在这里发现问题，于是gem给出失败的原因：
zlib is missing; necessary for building libxml2

所以说，问题的根据点在于如何安装zlib。

思路：（系统为Linux）

1.直接啃错误信息，不要怂就是看。经过翻译之后发现直接原因是gzdopen()函数没有，这个函数没有
是因为缺少了一个包：zlib，错误描述为：zlib is missing; necessary for building libxml2。根
据Linux的一贯作风，缺什么装什么就行。
2.发现原因之后，可以直接去百度当前系统如何安装zlib，但是，因为我有apt-get可以使用，于是，
直接上：apt-get install zlib加tag减，看一下都有哪些与zlib有关的可以直接安装的东西，发现了4
个：zlib1g    zlib1g-dbg    zlib1g-dev    zlibc
因为我这里需要调用zlib中的内容，本能的安装开发者包：zliblg-dev：
apt-get install zliblg-dev

然后发现，问题被巧妙的解决了。

问题二：用gem安装Ruby包又出错了

root@kali:~/Desktop#  gem install pg -v '0.20.0'

Building native extensions.  This could take a while...
ERROR:  Error installing pg:
ERROR: Failed to build gem native extension.

current directory: /var/lib/gems/2.3.0/gems/pg-0.20.0/ext
/usr/bin/ruby2.3 -r ./siteconf20171026-3597-1h17ktg.rb extconf.rb
checking for pg_config... yes
Using config values from /usr/bin/pg_config
You need to install postgresql-server-dev-X.Y for building a server-side extension or libpq-dev for building a client-side application.
You need to install postgresql-server-dev-X.Y for building a server-side extension or libpq-dev for building a client-side application.
checking for libpq-fe.h... no
Can't find the 'libpq-fe.h header
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary libraries and/or
headers.  Check the mkmf.log file for more details.  You may need configuration options.

Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/usr/bin/$(RUBY_BASE_NAME)2.3
--with-pg
--without-pg
--enable-windows-cross
--disable-windows-cross
--with-pg-config
--without-pg-config
--with-pg_config
--without-pg_config
--with-pg-dir
--without-pg-dir
--with-pg-include
--without-pg-include=${pg-dir}/include
--with-pg-lib
--without-pg-lib=${pg-dir}/lib

To see why this extension failed to compile, please check the mkmf.log which can be found here:

/var/lib/gems/2.3.0/extensions/x86_64-linux/2.3.0/pg-0.20.0/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in /var/lib/gems/2.3.0/gems/pg-0.20.0 for inspection.
Results logged to /var/lib/gems/2.3.0/extensions/x86_64-linux/2.3.0/pg-0.20.0/gem_make.out

解决方案：(这里的问题与上面的类似，于是先采用类似的方案尝试解决。最终解决方案如下)

apt-get install libpq-dev

问题三：强大的gem

root@kali:~/Desktop#  gem install sqlite3 -v '1.3.13'

Building native extensions.  This could take a while...
ERROR:  Error installing sqlite3:
ERROR: Failed to build gem native extension.

current directory: /var/lib/gems/2.3.0/gems/sqlite3-1.3.13/ext/sqlite3
/usr/bin/ruby2.3 -r ./siteconf20171026-6745-18q3rtn.rb extconf.rb
checking for sqlite3.h... no
sqlite3.h is missing. Try 'brew install sqlite3',
'yum install sqlite-devel' or 'apt-get install libsqlite3-dev'
and check your shared library search path (the
location where your sqlite3 shared library is located).
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/usr/bin/$(RUBY_BASE_NAME)2.3
--with-sqlite3-config
--without-sqlite3-config
--with-pkg-config
--without-pkg-config
--with-sqlite3-dir
--without-sqlite3-dir
--with-sqlite3-include
--without-sqlite3-include=${sqlite3-dir}/include
--with-sqlite3-lib
--without-sqlite3-lib=${sqlite3-dir}/lib

To see why this extension failed to compile, please check the mkmf.log which can be found here:

/var/lib/gems/2.3.0/extensions/x86_64-linux/2.3.0/sqlite3-1.3.13/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in /var/lib/gems/2.3.0/gems/sqlite3-1.3.13 for inspection.

解决方案：

这个例子中，有意思的地方在于gem不仅告诉你出现问题的原因，还给出了解决方案：
sqlite3.h is missing. Try 'brew install sqlite3','yum install sqlite-devel' or 'apt-get
install libsqlite3-dev' and check your shared library search path (the location where your
sqlite3 shared library is located).

这里给我的经验就是，一定要直接读错误信息，一定要读，一定要读。