Regexps
Search
Replace
Incremental searches in Emacs normally ignore the case of the text
they are searching through, if you specify the text in lower case.
Thus, if you specify searching for `foo', then `Foo' and
`foo' are also considered a match. Regexps, and in particular
character sets, are included: `[ab]' would match `a' or
`A' or `b' or `B'.
An upper-case letter anywhere in the incremental search string makes
the search case-sensitive. Thus, searching for `Foo' does not find
`foo' or `FOO'. This applies to regular expression search as
well as to string search. The effect ceases if you delete the
upper-case letter from the search string.
If you set the variable case-fold-search to nil, then
all letters must match exactly, including case. This is a per-buffer
variable; altering the variable affects only the current buffer, but
there is a default value which you can change as well. See Locals.
This variable applies to nonincremental searches also, including those
performed by the replace commands (see Replace) and the minibuffer
history matching commands (see Minibuffer History).
Regexps
Search
Replace