一、背景
apt-get install/remove在线安装/卸载文件真是方便极了。
但是有时候安装/卸载文件不清楚文件在服务器上的实际命名，例如想安装sndfile。应该执行下面哪个命令呢？
apt-get install sndfile
apt-get install libsndfile
正确答案是都不对。如何知道正确的命名呢？
二、查询文件命名
apt-cache一个非常有用的命令出来了。
（类比RedHat系的yum search）
. apt-cache search sndfile
查询的结果如下：
libsndfile1 - Library for reading/writing audio files
libsndfile1-dbg - debugging symbols for libsndfile
libsndfile1-dev - Development files for libsndfile; a library for reading/writing audio files
alure-doc - AL Utilities REtooled (documentation)
alure-utils - AL Utilities REtooled (utilities)
ir.lv2 - LV2 IR reverb
jack-capture - program for recording soundfiles with jack
kluppe - loop-player and recorder designed for live use
libalure-dev - AL Utilities REtooled (development files)
libalure1 - AL Utilities REtooled (shared library)
moc - ncurses based console audio player
python-soundfile - Python audio module based on libsndfile and NumPy
python3-soundfile - Python audio module based on libsndfile
qmmp - feature-rich audio player with support of many formats
samplerate-programs - Sample programs that use libsamplerate
silan - commandline tool to detect silence in audio-files
sndfile-programs - Sample programs that use libsndfile
sndfile-programs-dbg - debugging symbols for sndfile-programs
sndfile-tools - Collection of programs for operating on sound files
xmms2-plugin-sndfile - XMMS2 - sndfile decoder
zita-resampler - resampler application written with libzita-resampler
这个查询的有点太模糊了，含有字母s,n,d,f,i,l,e（甚至部分字母）的结果都出来了。
来个更准确一点的查询吧。
. apt-cache search sndfile|grep sndfile
查询的结果如下：
libsndfile1 - Library for reading/writing audio files
libsndfile1-dbg - debugging symbols for libsndfile
libsndfile1-dev - Development files for libsndfile; a library for reading/writing audio files
python-soundfile - Python audio module based on libsndfile and NumPy
python3-soundfile - Python audio module based on libsndfile
sndfile-programs - Sample programs that use libsndfile
sndfile-programs-dbg - debugging symbols for sndfile-programs
sndfile-tools - Collection of programs for operating on sound files
xmms2-plugin-sndfile - XMMS2 - sndfile decoder
结果清爽多了。
3. 现在知道了，安装sndfile的正确命令是
apt-get install libsndfile1
二、查询文件详细信息
apt-cache show libsndfile1
查询的结果片段如下：
...
Architecture: amd64
Source: libsndfile
Version: 1.0.-
Depends: libc6 (>= 2.14), libflac8 (>= 1.3.), libvorbisenc2 (>= 1.1.)
Filename: pool/main/libs/libsndfile/libsndfile1_1.0.25-10_amd64.deb
Size: ...
版本，依赖关系，文件大小什么的都出来了。
三、查询已安装文件
dpkg -l |grep libsndfile1
查询结果如下：
ii libsndfile1:amd64 1.0.-10ubuntu0.16.04. amd64 Library for reading/writing audio files
这个结果表明这个文件安装成功了。