Question

Both Ruby and Vim use “g” with substitution commands to mean “all occurrences.” What does the “g” stand for?

Specifically, in Ruby, the String class has two “sub” commands: sub will replace only the first occurrence, and gsub will replace all occurrences. For example:

string = "One potato, two potato, three potato, four."
string.sub('potato','banana') # => "One banana, two potato, three potato, four."
string.gsub('potato','banana') # => "One banana, two banana, three banana, four."

Similarly, in Vim, :%s/foo/bar will look through the whole file (which is what % means) and substitute one occurrence per line, but :%s/foo/bar/g will do all occurrences on each line.

My guess would be that in both cases, “g” means “greedy,” because both the Ruby commands and the Vim command accept a regular expression, but my understanding of greedy matching is “match the longest possible substring meeting these criteria,” not “match as many substrings as possible.” (See “Watch Out for The Greediness!“)

Answer 1

If I remember correctly it means global, which this Wiki page seems to confirm:

The g flag means global – each
occurrence in the line is changed,
rather than just the first.