GliderJan Varho

Natural Order String Comparisons in C

  • algorithms
  • C
  • MIT license
  • sort
  • source
  • strcmp
  • strnatcmp

I wrote a simple natural string order comparison function in C. I later found out I basically reimplemented (a part of) Martin Pool's strnatcmp, so I renamed mine that as well.

The idea is that in many cases the string "foo10bar" should sort after "foo9bar" instead of in between "foo1bar" and "foo2bar" as happens with strcmp.

I also made "foo02bar" sort after "foo1bar", but made sure "foo0.02bar" still sorts before "foo0.1bar" by considering anything beginning with dot a decimal.

Martin Pool's version also does something with lower/uppercase and leading space but I didn't need that, so mine is simpler and probably faster.

Examples:

strcmp("1", "2") = -1, strnatcmp("1", "2") = -1
strcmp("12", "1a") = -47, strnatcmp("12", "1a") = 1
strcmp("02", "1") = -1, strnatcmp("02", "1") = 1
strcmp("1 ", "1") = 32, strnatcmp("1 ", "1") = 32 
strcmp("0.02", "0.1") = -1, strnatcmp("0.02", "0.1") = -1
strcmp("0.02a", "0.0212a") = 48, strnatcmp("0.02a", "0.0212") = -2

Download: strnatcmp.c (2 KB) License: MIT license (Expat)

Filed under: C