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ftpmatch.md

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FTP wildcard matching

libcurl supports FTP wildcard matching. You use this feature by setting CURLOPT_WILDCARDMATCH to 1L and then use a "wildcard pattern" in the in the filename part of the URL.

Wildcard patterns

The default libcurl wildcard matching function supports:

* - ASTERISK

ftp://example.com/some/path/*.txt

To match all txt files in the directory some/path. Only two asterisks are allowed within the same pattern string.

? - QUESTION MARK"

A question mark matches any (exactly one) character. Like if you have files called photo1.jpeg and photo7.jpeg this pattern could match them:

ftp://example.com/some/path/photo?.jpeg

[ - BRACKET EXPRESSION

The left bracket opens a bracket expression. The question mark and asterisk have no special meaning in a bracket expression. Each bracket expression ends by the right bracket (]) and matches exactly one character. Some examples follow:

[a-zA-Z0-9] or [f-gF-G] - character intervals

[abc] - character enumeration

[^abc] or [!abc] - negation

[[:name:]] class expression. Supported classes are alnum, lower, space, alpha, digit, print, upper, blank, graph, xdigit.

[][-!^] - special case, matches only \-, ], [, ! or ^.

[\\[\\]\\\\] - escape syntax. Matches [, ] or \\.

Using the rules above, a filename pattern can be constructed:

ftp://example.com/some/path/[a-z[:upper:]\\\\].jpeg

FTP chunk callbacks

When FTP wildcard matching is used, the CURLOPT_CHUNK_BGN_FUNCTION callback is called before a transfer is initiated for a file that matches.

The callback can then opt to return one of these return codes to tell libcurl what to do with the file:

  • CURL_CHUNK_BGN_FUNC_OK transfer the file
  • CURL_CHUNK_BGN_FUNC_SKIP
  • CURL_CHUNK_BGN_FUNC_FAIL stop because of error

After the matched file has been transferred or skipped, the CURLOPT_CHUNK_END_FUNCTION callback is called.

The end chunk callback can only return success or error.

FTP matching callback

If the default pattern matching function is not to your liking, you can provide your own replacement function by setting the CURLOPT_FNMATCH_FUNCTION option to your alternative.