If the arguments to a replace command are in lower case, it preserves case when it makes a replacement. Thus, the command
M-x replace-string RET foo RET bar RET
replaces a lower case `foo' with a lower case `bar', an
all-caps `FOO' with `BAR', and a capitalized `Foo' with
`Bar'. (These three alternatives--lower case, all caps, and
capitalized, are the only ones that replace-string can
distinguish.)
If upper-case letters are used in the second argument, they remain
upper case every time that argument is inserted. If upper-case letters
are used in the first argument, the second argument is always
substituted exactly as given, with no case conversion. Likewise, if the
variable case-replace is set to nil, replacement is done
without case conversion. If case-fold-search is set to
nil, case is significant in matching occurrences of `foo' to
replace; this also inhibits case conversion of the replacement string.
Go to the first, previous, next, last section, table of contents.