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

NAME
     fetchMakeURL, fetchParseURL, 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 — file transfer functions

LIBRARY
     library “libfetch”

SYNOPSIS
     #include <sys/param.h>
     #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);

     void
     fetchFreeURL(struct url *u);

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

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

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

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

     struct url_ent *
     fetchListURL(const char *URL, const char *flags);

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

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

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

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

     struct url_ent *
     fetchList(struct url *u, const char *flags);

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

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

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

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

     struct url_ent *
     fetchListFile(struct url *u, const char *flags);

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

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

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

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

     struct url_ent *
     fetchListHTTP(struct url *u, const char *flags);

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

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

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

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

     struct url_ent *
     fetchListFTP(struct url *u, const char *flags);

DESCRIPTION
     These functions implement a high-level library for retrieving and upload‐
     ing files using Uniform 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 RFC1738.	 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, the following syn‐
     tax is assumed:

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

     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.

     fetchMakeURL() and fetchParseURL() 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

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

     The ims_time field stores the time value for If-Modified-Since HTTP
     requests.

     The pointer returned by fetchMakeURL() or fetchParseURL() should be freed
     using fetchFreeURL().

     fetchXGetURL(), fetchGetURL(), and fetchPutURL() constitute the recom‐
     mended 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 structure 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 modification 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 modification
     time.

     fetchListURL() attempts to list the contents of the directory pointed to
     by the URL provided.  If successful, it returns a malloced array of
     url_ent structures.  The url_ent structure is defined as follows in
     <fetch.h>:

     struct url_ent {
	 char	      name[PATH_MAX];
	 struct url_stat stat;
     };

     The list is terminated by an entry with an empty name.

     The pointer returned by fetchListURL() should be freed using free().

     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, respectively.  Note that although the
     implementation details of the individual access methods vary, it can gen‐
     erally 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.

FILE SCHEME
     fetchXGetFile(), fetchGetFile() and fetchPutFile() provide access to doc‐
     uments which are files in a locally mounted file system.  Only the <docu‐
     ment> 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 proto‐
     col as described in RFC959.

     If the ‘p’ (passive) flag is specified, a passive (rather than active)
     connection will be attempted.

     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 "anony‐
     mous@<hostname>".

HTTP SCHEME
     The fetchXGetHTTP(), fetchGetHTTP() and fetchPutHTTP() functions imple‐
     ment the HTTP/1.1 protocol.  With a little luck, there is even a chance
     that they comply with RFC2616 and RFC2617.

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

     If the ‘i’ (if-modified-since) flag is specified, and the ims_time field
     is set in struct url, then fetchXGetHTTP() and fetchGetHTTP() will send a
     conditional If-Modified-Since HTTP header to only fetch the content if it
     is newer than ims_time.

     Since there seems to be no good way of implementing the HTTP PUT method
     in a manner consistent 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 pro‐
     gram has the option of defining an authentication function with the fol‐
     lowing prototype:

     int myAuthMethod(struct url *u)

     The callback function should fill in the user and pwd fields in the pro‐
     vided 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 authen‐
     tication and the appropriate environment 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 individ‐
     ual 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 document, 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 hostname 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 provided in the URL.

     FTP_PROXY		 URL of the proxy to use for FTP requests.  The docu‐
			 ment part is ignored.	FTP and HTTP proxies are sup‐
			 ported; 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, the
			 “basic” and “digest” authorization methods are sup‐
			 ported.

			 Both methods require 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 speci‐
			 fied in the URL.

     HTTP_PROXY		 URL of the proxy to use for HTTP requests.  The docu‐
			 ment part is ignored.	Only HTTP proxies are sup‐
			 ported for HTTP requests.  If no port number is spec‐
			 ified, the default is 3128.

			 Note that this proxy will also be used for FTP docu‐
			 ments, 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 pass‐
			 word 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 format.  This
			 feature is experimental.

     NO_PROXY		 Either a single asterisk, which disables the use of
			 proxies altogether, or a comma- or whitespace-sepa‐
			 rated 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 avail‐
     able 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
     fetch(1), ftpio(3), ip(4)

     J. Postel and J. K. Reynolds, File Transfer Protocol, October 1985,
     RFC959.

     P. Deutsch, A. Emtage, and A. Marine., How to Use Anonymous FTP, May
     1994, RFC1635.

     T. Berners-Lee, L. Masinter, and M. McCahill, Uniform Resource Locators
     (URL), December 1994, RFC1738.

     R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach, and
     T. Berners-Lee, Hypertext Transfer Protocol -- HTTP/1.1, January 1999,
     RFC2616.

     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, RFC2617.

HISTORY
     The fetch library first appeared in FreeBSD 3.0.

AUTHORS
     The fetch library was mostly written by Dag-Erling Smørgrav
     ⟨des@FreeBSD.org⟩ with numerous suggestions and contributions from Jordan
     K. Hubbard ⟨jkh@FreeBSD.org⟩, Eugene Skepner ⟨eu@qub.com⟩, Hajimu Umemoto
     ⟨ume@FreeBSD.org⟩, Henry Whincup ⟨henry@techiebod.com⟩, Jukka A. Ukkonen
     ⟨jau@iki.fi⟩, Jean-François Dockes ⟨jf@dockes.org⟩ and others.  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 Smørgrav ⟨des@FreeBSD.org⟩.

BUGS
     Some parts of the library are not yet implemented.	 The most notable
     examples of this are fetchPutHTTP(), fetchListHTTP(), fetchListFTP() 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 26, 2010				   BSD
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