Clark J. Wang wrote: > In bash 3.0.14, the condition [[ file.txt =~ .*\\.txt\$ ]] returns TRUE but > in 3.2.39 it returns FALSE. But with the shopt option `compat31' set it also > returns TRUE. Is that reasonable? In the bash manual, `compat31' makes sense > only for quoted patterns. The string .*\\.txt\$ is considered to be quoted?
The manual says that any part of the pattern may be quoted to force it to be matched as a string. This is the behavior that compat31 turns off. The backslash is one of the shell's quoting characters, so portions of the pattern above are quoted. The question is how the shell processes those quoted characters. When compat31 is off, during expansion, the shell converts the characters quoted using shell quoting in a way that removes their special meaning from the regexp matcher. This forces the characters to match themselves. The pattern passed to the regular expression matcher is exactly ".*\\.txt\$", since the backslash is also how one quotes characters to the regexp matcher When compat31 is enabled, the shell performs all word expansions on the pattern, including quote removal, and passes the result to the regexp matcher. In this case, the pattern passed is ".*\.txt$", which is what you had in mind. Chet -- ``The lyf so short, the craft so long to lerne.'' - Chaucer Chet Ramey, ITS, CWRU [EMAIL PROTECTED] http://cnswww.cns.cwru.edu/~chet/
