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FETCH(3)			   BSD Library Functions Manual 			 FETCH(3)

NAME
     fetchMakeURL, fetchParseURL, fetchCopyURL, fetchFreeURL, fetchXGetURL, fetchGetURL,
     fetchPutURL, fetchStatURL, fetchListURL, fetchXGet, fetchGet, fetchPut, fetchStat,
     fetchList, fetchXGetFile, fetchGetFile, fetchPutFile, fetchStatFile, fetchListFile,
     fetchXGetHTTP, fetchGetHTTP, fetchPutHTTP, fetchStatHTTP, fetchListHTTP, fetchXGetFTP,
     fetchGetFTP, fetchPutFTP, fetchStatFTP, fetchListFTP fetchInitURLList, fetchFreeURLList,
     fetchUnquotePath, fetchUnquoteFilename, fetchStringifyURL, fetchConnectionCacheInit,
     fetchConnectionCacheClose, fetch -- file transfer functions

LIBRARY
     library ``libfetch''

SYNOPSIS
     #include <stdio.h>
     #include <fetch.h>

     struct url *
     fetchMakeURL(const char *scheme, const char *host, int port, const char *doc,
	 const char *user, const char *pwd);

     struct url *
     fetchParseURL(const char *URL);

     struct url *
     fetchCopyURL(const struct url *u);

     void
     fetchFreeURL(struct url *u);

     fetchIO *
     fetchXGetURL(const char *URL, struct url_stat *us, const char *flags);

     fetchIO *
     fetchGetURL(const char *URL, const char *flags);

     fetchIO *
     fetchPutURL(const char *URL, const char *flags);

     int
     fetchStatURL(const char *URL, struct url_stat *us, const char *flags);

     int
     fetchListURL(struct url_list *list, const char *URL, const char *flags);

     fetchIO *
     fetchXGet(struct url *u, struct url_stat *us, const char *flags);

     fetchIO *
     fetchGet(struct url *u, const char *flags);

     fetchIO *
     fetchPut(struct url *u, const char *flags);

     int
     fetchStat(struct url *u, struct url_stat *us, const char *flags);

     int
     fetchList(struct url_list *list, struct url *u, const char *flags);

     fetchIO *
     fetchXGetFile(struct url *u, struct url_stat *us, const char *flags);

     fetchIO *
     fetchGetFile(struct url *u, const char *flags);

     fetchIO *
     fetchPutFile(struct url *u, const char *flags);

     int
     fetchStatFile(struct url *u, struct url_stat *us, const char *flags);

     int
     fetchListFile(struct url_list *list, struct url *u, const char *flags);

     fetchIO *
     fetchXGetHTTP(struct url *u, struct url_stat *us, const char *flags);

     fetchIO *
     fetchGetHTTP(struct url *u, const char *flags);

     fetchIO *
     fetchPutHTTP(struct url *u, const char *flags);

     int
     fetchStatHTTP(struct url *u, struct url_stat *us, const char *flags);

     int
     fetchListHTTP(struct url_list *list, struct url *u, const char *flags);

     fetchIO *
     fetchXGetFTP(struct url *u, struct url_stat *us, const char *flags);

     fetchIO *
     fetchGetFTP(struct url *u, const char *flags);

     fetchIO *
     fetchPutFTP(struct url *u, const char *flags);

     int
     fetchStatFTP(struct url *u, struct url_stat *us, const char *flags);

     int
     fetchListFTP(struct url_list *list, struct url *u, const char *flags);

     void
     fetchInitURLList(struct url_list *ul);

     int
     fetchAppendURLList(struct url_list *dst, const struct url_list *src);

     void
     fetchFreeURLList(struct url_list *ul);

     char *
     fetchUnquotePath(struct url *u);

     char *
     fetchUnquoteFilename(struct url *u);

     char *
     fetchStringifyURL(const struct url *u);

     void
     fetchConnectionCacheInit(int global, int per_host);

     void
     fetchConnectionCacheClose(void);

DESCRIPTION
     These functions implement a high-level library for retrieving and uploading files using Uni-
     form Resource Locators (URLs).

     fetchParseURL() takes a URL in the form of a null-terminated string and splits it into its
     components function according to the Common Internet Scheme Syntax detailed in RFC 1738.  A
     regular expression which produces this syntax is:

	   <scheme>:(//(<user>(:<pwd>)?@)?<host>(:<port>)?)?/(<document>)?

     If the URL does not seem to begin with a scheme name, it is assumed to be a local path.
     Only absolute path names are accepted.

     Note that some components of the URL are not necessarily relevant to all URL schemes.  For
     instance, the file scheme only needs the <scheme> and <document> components.
     fetchParseURL() quotes any unsafe character in the URL automatically.  This is not done by
     fetchMakeURL().  fetchCopyURL() copies an existing url structure.

     fetchMakeURL(), fetchParseURL(), and fetchCopyURL() return a pointer to a url structure,
     which is defined as follows in <fetch.h>:

     #define URL_SCHEMELEN 16
     #define URL_USERLEN 256
     #define URL_PWDLEN 256
     #define URL_HOSTLEN 255

     struct url {
	 char	      scheme[URL_SCHEMELEN + 1];
	 char	      user[URL_USERLEN + 1];
	 char	      pwd[URL_PWDLEN + 1];
	 char	      host[URL_HOSTLEN + 1];
	 int	      port;
	 char	     *doc;
	 off_t	      offset;
	 size_t       length;
	 time_t       last_modified;
     };

     The pointer returned by fetchMakeURL(), fetchCopyURL(), and fetchParseURL() should be freed
     using fetchFreeURL().  The size of struct URL is not part of the ABI.

     fetchXGetURL(), fetchGetURL(), and fetchPutURL() constitute the recommended interface to the
     fetch library.  They examine the URL passed to them to determine the transfer method, and
     call the appropriate lower-level functions to perform the actual transfer.  fetchXGetURL()
     also returns the remote document's metadata in the url_stat structure pointed to by the us
     argument.

     The flags argument is a string of characters which specify transfer options.  The meaning of
     the individual flags is scheme-dependent, and is detailed in the appropriate section below.

     fetchStatURL() attempts to obtain the requested document's metadata and fill in the struc-
     ture pointed to by its second argument.  The url_stat structure is defined as follows in
     <fetch.h>:

     struct url_stat {
	 off_t	      size;
	 time_t       atime;
	 time_t       mtime;
     };

     If the size could not be obtained from the server, the size field is set to -1.  If the mod-
     ification time could not be obtained from the server, the mtime field is set to the epoch.
     If the access time could not be obtained from the server, the atime field is set to the mod-
     ification time.

     fetchListURL() attempts to list the contents of the directory pointed to by the URL pro-
     vided.  The pattern can be a simple glob-like expression as hint.	Callers should not depend
     on the server to filter names.  If successful, it appends the list of entries to the
     url_list structure.  The url_list structure is defined as follows in <fetch.h>:

     struct url_list {
	 size_t      length;
	 size_t      alloc_size;
	 struct url  *urls;
     };

     The list should be initialized by calling fetchInitURLList() and the entries be freed by
     calling fetchFreeURLList().  The function fetchAppendURLList() can be used to append one URL
     lists to another.	If the 'c' (cache result) flag is specified, the library is allowed to
     internally cache the result.

     fetchStringifyURL() returns the URL as string.  fetchUnquotePath() returns the path name
     part of the URL with any quoting undone.  Query arguments and fragment identifiers are not
     included.	fetchUnquoteFilename() returns the last component of the path name as returned by
     fetchUnquotePath().  fetchStringifyURL(), fetchUnquotePath(), and fetchUnquoteFilename()
     return a string that should be deallocated with free() after use.

     fetchConnectionCacheInit() enables the connection cache.  The first argument specifies the
     global limit on cached connections.  The second argument specifies the host limit.  Entries
     are considered to specify the same host, if the host name from the URL is identical, inde-
     pent of the address or address family.  fetchConnectionCacheClose() flushed the connection
     cache and closes all cached connections.

     fetchXGet(), fetchGet(), fetchPut(), and fetchStat() are similar to fetchXGetURL(),
     fetchGetURL(), fetchPutURL(), and fetchStatURL(), except that they expect a pre-parsed URL
     in the form of a pointer to a struct url rather than a string.

     All of the fetchXGetXXX(), fetchGetXXX(), and fetchPutXXX() functions return a pointer to a
     stream which can be used to read or write data from or to the requested document, respec-
     tively.  Note that although the implementation details of the individual access methods
     vary, it can generally be assumed that a stream returned by one of the fetchXGetXXX() or
     fetchGetXXX() functions is read-only, and that a stream returned by one of the fetchPutXXX()
     functions is write-only.

PROTOCOL INDEPENDENT FLAGS
     If the 'i' (if-modified-since) flag is specified, the library will try to fetch the content
     only if it is newer than last_modified.  For HTTP an If-Modified-Since HTTP header is sent.
     For FTP a MTDM command is sent first and compared locally.  For FILE the source file is com-
     pared.

FILE SCHEME
     fetchXGetFile(), fetchGetFile(), and fetchPutFile() provide access to documents which are
     files in a locally mounted file system.  Only the <document> component of the URL is used.

     fetchXGetFile() and fetchGetFile() do not accept any flags.

     fetchPutFile() accepts the 'a' (append to file) flag.  If that flag is specified, the data
     written to the stream returned by fetchPutFile() will be appended to the previous contents
     of the file, instead of replacing them.

FTP SCHEME
     fetchXGetFTP(), fetchGetFTP(), and fetchPutFTP() implement the FTP protocol as described in
     RFC 959.

     By default libfetch will attempt to use passive mode first and only fallback to active mode
     if the server reports a syntax error.  If the 'a' (active) flag is specified, a passive con-
     nection is not tried and active mode is used directly.

     If the 'l' (low) flag is specified, data sockets will be allocated in the low (or default)
     port range instead of the high port range (see ip(4)).

     If the 'd' (direct) flag is specified, fetchXGetFTP(), fetchGetFTP(), and fetchPutFTP() will
     use a direct connection even if a proxy server is defined.

     If no user name or password is given, the fetch library will attempt an anonymous login,
     with user name "anonymous" and password "anonymous@<hostname>".

HTTP SCHEME
     The fetchXGetHTTP(), fetchGetHTTP(), and fetchPutHTTP() functions implement the HTTP/1.1
     protocol.	With a little luck, there is even a chance that they comply with RFC 2616 and RFC
     2617.

     If the 'd' (direct) flag is specified, fetchXGetHTTP(), fetchGetHTTP(), and fetchPutHTTP()
     will use a direct connection even if a proxy server is defined.

     Since there seems to be no good way of implementing the HTTP PUT method in a manner consis-
     tent with the rest of the fetch library, fetchPutHTTP() is currently unimplemented.

AUTHENTICATION
     Apart from setting the appropriate environment variables and specifying the user name and
     password in the URL or the struct url, the calling program has the option of defining an
     authentication function with the following prototype:

     int myAuthMethod(struct url *u)

     The callback function should fill in the user and pwd fields in the provided struct url and
     return 0 on success, or any other value to indicate failure.

     To register the authentication callback, simply set fetchAuthMethod to point at it.  The
     callback will be used whenever a site requires authentication and the appropriate environ-
     ment variables are not set.

     This interface is experimental and may be subject to change.

RETURN VALUES
     fetchParseURL() returns a pointer to a struct url containing the individual components of
     the URL.  If it is unable to allocate memory, or the URL is syntactically incorrect,
     fetchParseURL() returns a NULL pointer.

     The fetchStat() functions return 0 on success and -1 on failure.

     All other functions return a stream pointer which may be used to access the requested docu-
     ment, or NULL if an error occurred.

     The following error codes are defined in <fetch.h>:

     [FETCH_ABORT]	 Operation aborted

     [FETCH_AUTH]	 Authentication failed

     [FETCH_DOWN]	 Service unavailable

     [FETCH_EXISTS]	 File exists

     [FETCH_FULL]	 File system full

     [FETCH_INFO]	 Informational response

     [FETCH_MEMORY]	 Insufficient memory

     [FETCH_MOVED]	 File has moved

     [FETCH_NETWORK]	 Network error

     [FETCH_OK] 	 No error

     [FETCH_PROTO]	 Protocol error

     [FETCH_RESOLV]	 Resolver error

     [FETCH_SERVER]	 Server error

     [FETCH_TEMP]	 Temporary error

     [FETCH_TIMEOUT]	 Operation timed out

     [FETCH_UNAVAIL]	 File is not available

     [FETCH_UNKNOWN]	 Unknown error

     [FETCH_URL]	 Invalid URL

     The accompanying error message includes a protocol-specific error code and message, e.g.
     "File is not available (404 Not Found)"

ENVIRONMENT
     FETCH_BIND_ADDRESS  Specifies a host name or IP address to which sockets used for outgoing
			 connections will be bound.

     FTP_LOGIN		 Default FTP login if none was provided in the URL.

     FTP_PASSIVE_MODE	 If set to anything but 'no', forces the FTP code to use passive mode.

     FTP_PASSWORD	 Default FTP password if the remote server requests one and none was pro-
			 vided in the URL.

     FTP_PROXY		 URL of the proxy to use for FTP requests.  The document part is ignored.
			 FTP and HTTP proxies are supported; if no scheme is specified, FTP is
			 assumed.  If the proxy is an FTP proxy, libfetch will send 'user@host'
			 as user name to the proxy, where 'user' is the real user name, and
			 'host' is the name of the FTP server.

			 If this variable is set to an empty string, no proxy will be used for
			 FTP requests, even if the HTTP_PROXY variable is set.

     ftp_proxy		 Same as FTP_PROXY, for compatibility.

     HTTP_AUTH		 Specifies HTTP authorization parameters as a colon-separated list of
			 items.  The first and second item are the authorization scheme and realm
			 respectively; further items are scheme-dependent.  Currently, only basic
			 authorization is supported.

			 Basic authorization requires two parameters: the user name and password,
			 in that order.

			 This variable is only used if the server requires authorization and no
			 user name or password was specified in the URL.

     HTTP_PROXY 	 URL of the proxy to use for HTTP requests.  The document part is
			 ignored.  Only HTTP proxies are supported for HTTP requests.  If no port
			 number is specified, the default is 3128.

			 Note that this proxy will also be used for FTP documents, unless the
			 FTP_PROXY variable is set.

     http_proxy 	 Same as HTTP_PROXY, for compatibility.

     HTTP_PROXY_AUTH	 Specifies authorization parameters for the HTTP proxy in the same format
			 as the HTTP_AUTH variable.

			 This variable is used if and only if connected to an HTTP proxy, and is
			 ignored if a user and/or a password were specified in the proxy URL.

     HTTP_REFERER	 Specifies the referrer URL to use for HTTP requests.  If set to
			 ``auto'', the document URL will be used as referrer URL.

     HTTP_USER_AGENT	 Specifies the User-Agent string to use for HTTP requests.  This can be
			 useful when working with HTTP origin or proxy servers that differentiate
			 between user agents.

     NETRC		 Specifies a file to use instead of ~/.netrc to look up login names and
			 passwords for FTP sites.  See ftp(1) for a description of the file for-
			 mat.  This feature is experimental.

     NO_PROXY		 Either a single asterisk, which disables the use of proxies altogether,
			 or a comma- or whitespace-separated list of hosts for which proxies
			 should not be used.

     no_proxy		 Same as NO_PROXY, for compatibility.

EXAMPLES
     To access a proxy server on proxy.example.com port 8080, set the HTTP_PROXY environment
     variable in a manner similar to this:

	   HTTP_PROXY=http://proxy.example.com:8080

     If the proxy server requires authentication, there are two options available for passing the
     authentication data.  The first method is by using the proxy URL:

	   HTTP_PROXY=http://<user>:<pwd>@proxy.example.com:8080

     The second method is by using the HTTP_PROXY_AUTH environment variable:

	   HTTP_PROXY=http://proxy.example.com:8080
	   HTTP_PROXY_AUTH=basic:*:<user>:<pwd>

     To disable the use of a proxy for an HTTP server running on the local host, define NO_PROXY
     as follows:

	   NO_PROXY=localhost,127.0.0.1

SEE ALSO
     ftp(1), ip(4)

     J. Postel and J. K. Reynolds, File Transfer Protocol, October 1985, RFC 959.

     P. Deutsch, A. Emtage, and A. Marine, How to Use Anonymous FTP, May 1994, RFC 1635.

     T. Berners-Lee, L. Masinter, and M. McCahill, Uniform Resource Locators (URL), December
     1994, RFC 1738.

     R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach, and T. Berners-Lee,
     Hypertext Transfer Protocol -- HTTP/1.1, January 1999, RFC 2616.

     J. Franks, P. Hallam-Baker, J. Hostetler, S. Lawrence, P. Leach, A. Luotonen, and L.
     Stewart, HTTP Authentication: Basic and Digest Access Authentication, June 1999, RFC 2617.

HISTORY
     The fetch library first appeared in FreeBSD 3.0.

AUTHORS
     The fetch library was mostly written by Dag-Erling Smorgrav <des@FreeBSD.org> with numerous
     suggestions from Jordan K. Hubbard <jkh@FreeBSD.org>, Eugene Skepner <eu@qub.com> and other
     FreeBSD developers.  It replaces the older ftpio library written by Poul-Henning Kamp
     <phk@FreeBSD.org> and Jordan K. Hubbard <jkh@FreeBSD.org>.

     This manual page was written by Dag-Erling Smorgrav <des@FreeBSD.org>.

BUGS
     Some parts of the library are not yet implemented.  The most notable examples of this are
     fetchPutHTTP() and FTP proxy support.

     There is no way to select a proxy at run-time other than setting the HTTP_PROXY or FTP_PROXY
     environment variables as appropriate.

     libfetch does not understand or obey 305 (Use Proxy) replies.

     Error numbers are unique only within a certain context; the error codes used for FTP and
     HTTP overlap, as do those used for resolver and system errors.  For instance, error code 202
     means "Command not implemented, superfluous at this site" in an FTP context and "Accepted"
     in an HTTP context.

     fetchStatFTP() does not check that the result of an MDTM command is a valid date.

     The man page is incomplete, poorly written and produces badly formatted text.

     The error reporting mechanism is unsatisfactory.

     Some parts of the code are not fully reentrant.

BSD					 January 22, 2010				      BSD
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