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FETCH(3) 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
File Transfer Library (libfetch, -lfetch)
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 *pattern,
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 *pattern,
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 *pattern,
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 *pattern,
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 *pattern,
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 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 RFC 1738. A regular expression which produces
this syntax is:
<scheme>:(//(<user>(:<pwd>)?@)?<host>(:<port>)?)?/(<doc>)?
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
<doc> 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 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. 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, indepent 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, 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.
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 compared.
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 connection 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 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
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 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 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 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 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
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 format.
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 Sm/orgrav
<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 Sm/orgrav <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.
NetBSD 10.99 January 22, 2010 NetBSD 10.99