Unconditional Replace
Replace
Replacement and Case
The M-x replace-string command replaces exact matches for a single string. The similar command M-x replace-regexp replaces any match for a specified pattern.
In replace-regexp, the newstring need not be constant: it
can refer to all or part of what is matched by the regexp.
`\&' in newstring stands for the entire match being replaced.
`\d' in newstring, where d is a digit, stands for
whatever matched the dth parenthesized grouping in regexp.
To include a `\' in the text to replace with, you must enter
`\\'. For example,
M-x replace-regexpRETc[ad]+rRET\&-safeRET
replaces (for example) `cadr' with `cadr-safe' and `cddr'
with `cddr-safe'.
M-x replace-regexpRET\(c[ad]+r\)-safeRET\1RET
performs the inverse transformation.