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====== BASH - Commands - sort - Numeric Sort Bug ======

A test file:

<file bash test.txt>
192.168.1.123.25:12345
10.0.0.1:80
192.168.1.123.125:12345
10.0.0.1:8080
</file>

----

<code bash>
sort -n test.txt | uniq
</code>

returns:

<code bash>
10.0.0.1:80
10.0.0.1:8080
192.168.1.123.125:12345
192.168.1.123.25:12345
</code>

----

<code bash>
sort -un test.txt
</code>

returns:

<code bash>
10.0.0.1:80
192.168.1.123.25:12345
</code>

<WRAP info>
**NOTE:**   The **info** page for sort does explain this behavior, though the **man** has no mention of it: 

Numeric sort uses what might be considered an unconventional method to compare strings representing floating point numbers.

Rather than first converting each string to the C `double' type and then comparing those values, `sort' aligns the decimal-point characters in the two strings and compares the strings a character at a time.

One benefit of using this approach is its speed.  In practice this is much more efficient than performing the two corresponding string-to-double (or even string-to-integer) conversions and then comparing doubles.

In addition, there is no corresponding loss of precision.

Converting each string to `double' before comparison would limit precision to about 16 digits on most systems.


</WRAP>

----

===== Use sort to correctly sort IP addresses =====

<code bash>
sort -t . -k1,1n -k2,2n -k3,3n -k4,4n test.txt
</code>

returns:

<code bash>
10.0.0.1:80
10.0.0.1:8080
192.168.1.123.125:12345
192.168.1.123.25:12345
</code>