This operator can match the empty string either at the beginning of the string or after a newline character. Thus, it is said to anchor the pattern to the beginning of a line.
In the cases following, ‘^’ represents this operator. (Otherwise, ‘^’ is ordinary.)
RE_CONTEXT_INDEP_ANCHORSis set, and it is outside a bracket expression.
These rules imply that some valid patterns containing ‘^’ cannot be
matched; for example, ‘foo^bar’ if
not_bol field is set in the pattern buffer (see GNU Pattern Buffers), then ‘^’ fails to match at the beginning of the
string. This lets you match against pieces of a line, as you would need to if,
say, searching for repeated instances of a given pattern in a line; it
would work correctly for patterns both with and without