.Bf -symbolic This interface is made obsolete by regex(3).
The re_comp function compiles a string into an internal form suitable for pattern matching. The re_exec function checks the argument string against the last string passed to re_comp.
The re_comp function returns 0 if the string s was compiled successfully; otherwise a string containing an error message is returned. If re_comp is passed 0 or a null string, it returns without changing the currently compiled regular expression.
The re_exec function returns 1 if the string s matches the last compiled regular expression, 0 if the string s failed to match the last compiled regular expression, and -1 if the compiled regular expression was invalid (indicating an internal error).
The strings passed to both re_comp and re_exec may have trailing or embedded newline characters; they are terminated by NUL s. The regular expressions recognized are described in the manual entry for ed(1), given the above difference.
The re_exec function returns -1 for an internal error.
The re_comp function returns one of the following strings if an error occurs:
No previous regular expression,
Regular expression too long,
too many \(\) pairs,
ed(1), egrep(1), ex(1), fgrep(1), grep(1), regex(3)