What's the difference between --general-numeric-sort and --numeric-sort options in gnu sort

Question

sort provides two kinds of numeric sort. This is from the man page:

   -g, --general-numeric-sort
          compare according to general numeric         


        

Answer 1

In addition to the accepted answer which mention -g allow scientific notation, I want to shows the part which most likely causes undesirable behavior.

With -g:

$ LC_COLLATE=fr_FR.UTF-8 LC_NUMERIC=en_US.UTF-8 sort -g myfile
baa
--inf
--inf  
--inf- 
--inf--
--inf-a
--nnf
nnf--
   nnn  
tnan
zoo
   naN
Nana
nani lol
-inf
-inf--
-11
-2
-1
1
+1
2
+2
0xa
11
+11
inf

Look at the zoo, three important things here:

• Line starts with NAN(e.g. Nana and nani lol) or -INF(single dash, not --INF) move to end but before digits. While INF move to the last after digits because it means infinity.

• The NAN, INF, and -INF are case insensitive.

• The lines always ignore whitespace from either side of NAN, INF, -INF (regardless of LC_CTYPE). Other alphabetic may ignore whitespace from either side depends on locale LC_COLLATE (e.g. LC_COLLATE=fr_FR.UTF-8 ignore but LC_COLLATE=us_EN.UTF-8 not ignore).

So if you are sorting arbitrary alphanumeric then you probably don't want -g. If you really need scientific notation comparison with -g, then you probably want to extract alphabet and numeric data and do comparison separately.

If you only need ordinary number(e.g. 1, -1) sorting, and feel that 0x/E/+ sorting not important, just use -n enough:

$ LC_COLLATE=fr_FR.UTF-8 LC_NUMERIC=en_US.UTF-8 sort -n myfile
-1000
-22
-13
-11
-010
-10
-5
-2
-1
-0.2
-0.12
-0.11
-0.1
0x1
0x11
0xb
+1
+11
+2
-a
-aa
--aa
-aaa
-b
baa
BAA
bbb
+ignore
inf
-inf
--inf
--inf  
--inf- 
--inf--
-inf--
--inf-a
   naN
Nana
nani lol
--nnf
nnf--
   nnn  
None         
uum
Zero cool
-zzz
1
1.1
1.234E10
5
11

Either of -g or -n, be aware of locale effect. You may want to specify LC_NUMERIC as us_EN.UTF-8 to avoid fr_FR.UTF-8 sort - with floating number failed:

$ LC_COLLATE=fr_FR.UTF-8 LC_NUMERIC=fr_FR.UTF-8 sort -n myfile
-10
-5
-2
-1
-1.1
-1.2
-0.1
-0.11
-0.12
-0.2
-a
+b
middle
-wwe
+zoo
1
1.1

With LC_NUMERIC=en_US.UTF-8:

$ LC_COLLATE=fr_FR.UTF-8 LC_NUMERIC=en_US.UTF-8 sort -n myfile
-10
-5
-2
-1.2
-1.1
-1
-0.2
-0.12
-0.11
-0.1
-a
+b
middle
-wwe
+zoo
1
1.1

Or LC_NUMERIC=us_EN.UTF-8 to group +|-|space with alpha:

$ LC_COLLATE=fr_FR.UTF-8 LC_NUMERIC=us_EN.UTF-8 sort -n myfile
-0.1
    a
    b
 a
 b
+b
+zoo
-a
-wwe
middle
1

You probably want to specify locale when using sort if want to write portable script.