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
File Transfer Library (libfetch, -lfetch)
#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);
These functions implement a high-level library for retrieving and uploading
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 syntax
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;
};
The pointer returned by fetchMakeURL() or fetchParseURL() should be freed
using fetchFreeURL().
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 lowerlevel
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
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 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.
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.
fetchXGetFTP(), fetchGetFTP() and fetchPutFTP() implement the FTP protocol
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 "anonymous@<hostname>".
The fetchXGetHTTP(), fetchGetHTTP() and fetchPutHTTP() functions implement
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.
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 environment variables aren't set.
This interface is experimental and may be subject to change.
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 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)"
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 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 colonseparated
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 format. This
feature is experimental.
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>
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.
The fetch library first appeared in FreeBSD 3.0.
The fetch library was mostly written by Dag-Erling Coidan Smorgrav
<[email protected]> with numerous suggestions from Jordan K. Hubbard
<[email protected]>, Eugene Skepner <[email protected]> and other FreeBSD developers.
It replaces the older ftpio library written by Poul-Henning Kamp
<[email protected]> and Jordan K. Hubbard <[email protected]>.
This manual page was written by Dag-Erling Coidan Smorgrav
<[email protected]>.
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.
FreeBSD 5.2.1 July 1, 1998 FreeBSD 5.2.1 [ Back ] |
