blocks|key|4546714|text|若要以独立于发行版的方式执行此操作，可以在grep中使用ldconfig，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4546715|ldconfig+-p+%7C+grep+libjpeg|code-block|syntax|javascript|4546716|如果没有安装libjpeg，就不会有输出。如果安装了它，您将得到每个可用版本的一行。|4546717|用任何您想要的库替换libjpeg，并且您有一种通用的、与发行版无关的*检查库可用性的方法。|4546718|如果由于某种原因没有设置ldconfig的路径，可以尝试使用它的完整路径(通常是/sbin/ldconfig+)来调用它。|offset|length|style|CODE|4546719|*99%25的次数*|entityMap^0|0|0|0|0|14|E|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|U|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|V|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|W|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|X|8|@$M|Y|N|Z|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|10|8|@]|9|@]|A|$]]]|S|$]]

To do this in a distro-independent* fashion you can use ldconfig with grep, like this:

<pre><code>ldconfig -p | grep libjpeg
</code></pre>

If libjpeg is not installed, there will be no output. If it is installed, you will get a line for each version available. 

Replace libjpeg by any library you want, and you have a generic, distro-independent* way of checking for library availability.

If for some reason the path to ldconfig is not set, you can try to invoke it using its full path, usually <code>/sbin/ldconfig</code>.

**99% of the times*

blocks|key|4546509|text|您可以向您的发行版的包经理查询(智能，yum，.)但由于你没有给出你的分配，我不能给你正确的命令。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4546510|另一种方法是运行gcc+-ljpeg，如果您得到'ld:+library+not+-ljpeg‘，这意味着gcc没有找到这个库(但这并不意味着它没有安装)，如果您得到’未定义的符号："_main"，引用于：.‘这意味着libjpeg已经被发现了。|offset|length|style|CODE|4546511|locate+libjpeg;+ls+/usr/lib/libjpeg*;+ls+/lib/libjpeg*是查找系统中是否安装了库的另一种方法。|4546512|如果您给我们更多的上下文(为什么您需要检查libjpeg是否已经安装)，还有很多其他的检查方法，我们可以为您的具体情况提供最好的解决方案。|entityMap^0|0|8|A|0|0|1I|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@$D|O|E|P|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|Q|8|@$D|R|E|S|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|T|8|@]|9|@]|A|$]]]|L|$]]

You can check with the package manager of your distribution (aptitude, yum, ...) but as you did not give your distribution I can't give you the right command.

Another way can be to run <code>gcc -ljpeg</code>, if you get 'ld: library not found for -ljpeg' it means that gcc has not found the library (but it don't mean that it's not installed), if you get something like 'Undefined symbols: "_main", referenced from: ...' it means that libjpeg has been found.

<code>locate libjpeg; ls /usr/lib/libjpeg*; ls /lib/libjpeg*</code> are some other way to find if the lib in installed in the system

There is many other way to check that, if you give us more context (why you need to check if libjpeg is installed) we could give you the best solution for your specific case.

blocks|key|4546635|text|我使用whereis实用程序。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4546636|示例：|4546637|l1feh4ck3r@xxx:~$+whereis+libjpeg
libjpeg:+/usr/lib/libjpeg.so+/usr/lib/libjpeg.a+/usr/lib/libjpeg.la|code-block|syntax|javascript|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|L|8|@]|9|@]|A|$G|H]]]|I|$]]

I use the whereis utility.

Sample:

<pre><code>l1feh4ck3r@xxx:~$ whereis libjpeg
libjpeg: /usr/lib/libjpeg.so /usr/lib/libjpeg.a /usr/lib/libjpeg.la
</code></pre>

blocks|key|807686|text|对于基于deb的发行版，您可以这样做。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|807687|dpkg+-s+packagename|code-block|syntax|javascript|807688|或者如果您只知道文件名，请使用|807689|locate+filename|807690|文件名通常是libsomething.so.version。|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|O|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|P|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|Q|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|R|8|@]|9|@]|A|$]]]|M|$]]

For deb-based distribution you can do

<pre><code>dpkg -s packagename
</code></pre>

Or if you know the filename only, use

<pre><code>locate filename
</code></pre>

The filename is usually libsomething.so[.version].

blocks|key|4546757|text|我用这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4546758|gcc+-lpng|code-block|syntax|javascript|4546759|当安装库时，它会产生：|4546760|undefined+reference+to+'main'|4546761|当库未安装时：|4546762|cannot+find+-lpng|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Q|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|R|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|T|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|U|8|@]|9|@]|A|$E|F]]]|O|$]]

I use this:

<pre><code>gcc -lpng
</code></pre>

When the lib is installed, it yields:

<pre><code>undefined reference to 'main'
</code></pre>

When the lib is not installed:

<pre><code>cannot find -lpng
</code></pre>

blocks|key|808011|text|在Ubuntu20.04上，我可以使用智能显示软件包的大量相关信息。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|808012|%25+aptitude+show+libssl-dev
Package:+libssl-dev++++++++++++++++++++++
Version:+1.1.1f-1ubuntu2.1
State:+installed
Automatically+installed:+no
Multi-Arch:+same
Priority:+optional
Section:+libdevel
Maintainer:+Ubuntu+Developers+<ubuntu-devel-discuss@lists.ubuntu.com>
Architecture:+amd64
Uncompressed+Size:+8,006+k
Depends:+libssl1.1+(=+1.1.1f-1ubuntu2.1)
Suggests:+libssl-doc
Conflicts:+libssl1.0-dev
Breaks:+libssl-dev:i386+(!=+1.1.1f-1ubuntu2.1)
Replaces:+libssl-dev:i386+(<+1.1.1f-1ubuntu2.1)
Description:+Secure+Sockets+Layer+toolkit+-+development+files
+This+package+is+part+of+the+OpenSSL+project's+implementation+of+the+SSL+and+TLS+cryptographic+protocols+for+secure+communication+over
+the+Internet.+
+
+It+contains+development+libraries,+header+files,+and+manpages+for+libssl+and+libcrypto.
Homepage:+https://www.openssl.org/|code-block|syntax|javascript|808013|要找到提供特定文件的包，我发现apt-file非常有用-下面是一些说明：https://linuxhint.com/find_哪一个_套餐_包含_特定的_文件_ubuntu/|offset|length|style|CODE|808014|%25+apt-file+search+'libjpeg.so'++++++++++
darktable:+/usr/lib/x86_64-linux-gnu/darktable/plugins/imageio/format/libjpeg.so
libjpeg-turbo8:+/usr/lib/x86_64-linux-gnu/libjpeg.so.8
libjpeg-turbo8:+/usr/lib/x86_64-linux-gnu/libjpeg.so.8.2.2
libjpeg-turbo8-dev:+/usr/lib/x86_64-linux-gnu/libjpeg.so
libjpeg62:+/usr/lib/x86_64-linux-gnu/libjpeg.so.62
libjpeg62:+/usr/lib/x86_64-linux-gnu/libjpeg.so.62.0.0
libjpeg62-dev:+/usr/lib/x86_64-linux-gnu/libjpeg.so
libjpeg9:+/usr/lib/x86_64-linux-gnu/libjpeg.so.9
libjpeg9:+/usr/lib/x86_64-linux-gnu/libjpeg.so.9.4.0
libjpeg9-dev:+/usr/lib/x86_64-linux-gnu/libjpeg.so
libxine2-misc-plugins:+/usr/lib/x86_64-linux-gnu/xine/plugins/2.7/xineplug_decode_libjpeg.so
nsight-systems:+/usr/lib/nsight-systems/Host-x86_64/libjpeg.so.8|entityMap|0|LINK|mutability|MUTABLE|url|https://linuxhint.com/find_which_package_contains_specific_file_ubuntu/^0|0|0|F|8|10|1F|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|W|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|X|8|@$I|Y|J|Z|K|L]]|9|@$I|10|J|11|1|12]]|A|$]]|$1|M|3|N|5|D|7|13|8|@]|9|@]|A|$E|F]]]|O|$P|$5|Q|R|S|A|$T|U]]]]

On Ubuntu 20.04, I am able to display a wealth of relevant information for a package using aptitude.
<pre><code>% aptitude show libssl-dev
Package: libssl-dev 
Version: 1.1.1f-1ubuntu2.1
State: installed
Automatically installed: no
Multi-Arch: same
Priority: optional
Section: libdevel
Maintainer: Ubuntu Developers &lt;ubuntu-devel-discuss@lists.ubuntu.com&gt;
Architecture: amd64
Uncompressed Size: 8,006 k
Depends: libssl1.1 (= 1.1.1f-1ubuntu2.1)
Suggests: libssl-doc
Conflicts: libssl1.0-dev
Breaks: libssl-dev:i386 (!= 1.1.1f-1ubuntu2.1)
Replaces: libssl-dev:i386 (&lt; 1.1.1f-1ubuntu2.1)
Description: Secure Sockets Layer toolkit - development files
 This package is part of the OpenSSL project's implementation of the SSL and TLS cryptographic protocols for secure communication over
 the Internet. 
 
 It contains development libraries, header files, and manpages for libssl and libcrypto.
Homepage: https://www.openssl.org/

</code></pre>
To find which package would provide a particular file I have found <code>apt-file</code> very useful - some instructions are here: <a href="https://linuxhint.com/find_which_package_contains_specific_file_ubuntu/" rel="nofollow noreferrer">https://linuxhint.com/find_which_package_contains_specific_file_ubuntu/</a>
<pre><code>% apt-file search 'libjpeg.so' 
darktable: /usr/lib/x86_64-linux-gnu/darktable/plugins/imageio/format/libjpeg.so
libjpeg-turbo8: /usr/lib/x86_64-linux-gnu/libjpeg.so.8
libjpeg-turbo8: /usr/lib/x86_64-linux-gnu/libjpeg.so.8.2.2
libjpeg-turbo8-dev: /usr/lib/x86_64-linux-gnu/libjpeg.so
libjpeg62: /usr/lib/x86_64-linux-gnu/libjpeg.so.62
libjpeg62: /usr/lib/x86_64-linux-gnu/libjpeg.so.62.0.0
libjpeg62-dev: /usr/lib/x86_64-linux-gnu/libjpeg.so
libjpeg9: /usr/lib/x86_64-linux-gnu/libjpeg.so.9
libjpeg9: /usr/lib/x86_64-linux-gnu/libjpeg.so.9.4.0
libjpeg9-dev: /usr/lib/x86_64-linux-gnu/libjpeg.so
libxine2-misc-plugins: /usr/lib/x86_64-linux-gnu/xine/plugins/2.7/xineplug_decode_libjpeg.so
nsight-systems: /usr/lib/nsight-systems/Host-x86_64/libjpeg.so.8

</code></pre>

blocks|key|4546810|text|您也可以尝试使用dpkg来检查它是否已安装。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4546811|dpkg+--list+%7C+grep+[some_key_words_of_your_lib]|offset|length|style|CODE|4546812|另外，在CentOS上，你可以试试这个。|4546813|rpm+-qa+[lib_name]|entityMap^0|0|0|1B|0|0|0|I^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@$D|O|E|P|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|Q|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|R|8|@$D|S|E|T|F|G]]|9|@]|A|$]]]|L|$]]

You can also try using dpkg to check whether it is installed.

<code>dpkg --list | grep [some_key_words_of_your_lib]</code>

Besides, on CentOS, you can try this.

<code>rpm -qa [lib_name]</code>

blocks|key|808036|text|如上文所述|type|unstyled|depth|inlineStyleRanges|entityRanges|data|808037|dpkg+-s包装名称|blockquote|808038|[[+$(dpkg+-s+libsox-fmt-pulse+2>+/dev/null)+=~+"is+not+installed"+]]+&&+sudo+apt+install+libsox-fmt-pulse+#+for+hdmi+output|code-block|syntax|javascript|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$]]|$1|E|3|F|5|G|7|M|8|@]|9|@]|A|$H|I]]]|J|$]]

as per Kim above
<blockquote>
dpkg -s packagename
</blockquote>
<pre><code>[[ $(dpkg -s libsox-fmt-pulse 2&gt; /dev/null) =~ &quot;is not installed&quot; ]] &amp;&amp; sudo apt install libsox-fmt-pulse # for hdmi output
</code></pre>

In Linux, how do I check if a library is installed or not? (from the command line of course).

In my specific case now, I want to check whether libjpeg is installed.

How to check if a library is installed?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在Linux中，如何检查是否安装了库？(当然是从命令行)。在我现在的具体案例中，我想检查libjpeg是否已经安装。

问如何检查是否安装了库？
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