fetchFreeURL(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
File Transfer Library (libfetch, -lfetch)
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 * 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>: char pwd[URL_PWDLEN+1]; char host[MAXHOSTNAMELEN+1]; int port; char *doc; off_t offset; size_t length; }; 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[MAXPATHLEN]; 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 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's 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. 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 aren't set. 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- 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 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.
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:
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 Smorgrav <des@FreeBSD.org> with numerous suggestions from Jordan K. Hubbard <jkh@FreeBSD.org>, Eugene Skepner <eu@qub.com> and other FreeBSD develop- ers. It replaces the older ftpio library written by Poul-Henning Kamp <pkh@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(), fetchListHTTP(), fetchListFTP() and FTP proxy support. There's 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.
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