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 retriev
ing 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 Com
mon Internet Scheme Syntax detailed in RFC1738. A regular expression
which produces this syntax is:: <scheme>:(//(<user>(:<pwd>)?@)?<host>(:<port>)?)?/(<doc; ument>)?
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
#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 appro
priate 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-de
pendent, 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
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 mod
ification time.
fetchListURL() attempts to list the contents of the directo
ry 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
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 sim
ilar 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 al
though 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 re
turned by one
of the fetchPutXXX() functions is write-only.

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 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 al
located 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() func
tions implement 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.
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 re
quires 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 mem
ory, 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_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 sock: ets used for outgoing connections; will be bound.
FTP_LOGIN Default FTP login if none was pro
vided 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 re
quests. The: document part is ignored. FTP and; HTTP proxies
are supported; if no scheme is spec; ified, 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 compatibili
ty.
HTTP_AUTH Specifies HTTP authorization parame
ters as a: colon-separated list of items. The; first and
second item are the authorization; scheme and
realm respectively; further items; are schemedependent. Currently, only basic; authorization
is supported.; Basic authorization requires two pa; rameters: the
user name and password, in that or; der.; 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 re
quests. 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 compatibili
ty.
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.

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

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(), 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 appropri
ate.
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 im
plemented, 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 bad
ly formatted text.
The error reporting mechanism is unsatisfactory.
Some parts of the code are not fully reentrant.
BSD July 1, 1998

docs.sk

comprehensive documentation repository

See also

fetch(3)

NAME

LIBRARY

SYNOPSIS

DESCRIPTION

FILE SCHEME

FTP SCHEME

HTTP SCHEME

AUTHENTICATION

RETURN VALUES

ENVIRONMENT

EXAMPLES

SEE ALSO

HISTORY

AUTHORS

BUGS