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FETCH(3)               FreeBSD Library Functions Manual               FETCH(3)

     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);

     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);

     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);

     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);

     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);

     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);

     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:


     If the URL does not seem to begin with a scheme name, the following
     syntax is assumed:


     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

     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 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

     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

     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
     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

     fetchXGetFTP(), fetchGetFTP() and fetchPutFTP() implement the FTP
     protocol as described in RFC959.

     If the `P' (not passive) flag is specified, an active (rather than
     passive) connection will be attempted.

     The `p' flag is supported for compatibility with earlier versions where
     active connections were the default.  It has precedence over the `P'
     flag, so if both are specified, fetchMakeURL will use a passive

     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

     If no user name or password is given, the fetch library will attempt an
     anonymous login, with user name "anonymous" and password

     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 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

     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.

     Based on HTTP SCHEME.  By default the peer is verified using the CA
     bundle located in /etc/ssl/cert.pem.  The file may contain multiple CA
     certificates.  A common source of a current CA bundle is

     The CA bundle used for peer verification can be changed by setting the
     environment variables SSL_CA_CERT_FILE to point to a concatenated bundle
     of trusted certificates and SSL_CA_CERT_PATH to point to a directory
     containing hashes of trusted CAs (see verify(1)).

     A certificate revocation list (CRL) can be used by setting the
     environment variable SSL_CRL_FILE (see crl(1)).

     Peer verification can be disabled by setting the environment variable
     SSL_NO_VERIFY_PEER.  Note that this also disables CRL checking.

     By default the service identity is verified according to the rules
     detailed in RFC6125 (also known as hostname verification).  This feature
     can be disabled by setting the environment variable

     Client certificate based authentication is supported.  The environment
     variable SSL_CLIENT_CERT_FILE should be set to point to a file containing
     key and client certificate to be used in PEM format. In case the key is
     stored in a separate file, the environment variable SSL_CLIENT_KEY_FILE
     can be set to point to the key in PEM format.  In case the key uses a
     password, the user will be prompted on standard input (see PEM(3)).

     By default libfetch allows TLSv1 and newer when negotiating the
     connecting with the remote peer.  You can change this behavior by setting
     the SSL_ALLOW_SSL3 environment variable to allow SSLv3 and SSL_NO_TLS1,
     SSL_NO_TLS1_1 and SSL_NO_TLS1_2 to disable TLS 1.0, 1.1 and 1.2

     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.

     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

     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

     FTP_LOGIN               Default FTP login if none was provided in the

     FTP_PASSIVE_MODE        If set to `no', forces the FTP code to use active
                             mode.  If set to any other value, forces passive
                             mode even if the application requested active

     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_ACCEPT             Specifies the value of the Accept header for HTTP
                             requests.  If empty, no Accept header is sent.
                             The default is ``*/*''.

     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 supported.

                             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
                             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

                             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.  If defined but empty, no
                             User-Agent header is sent.

     NETRC                   Specifies a file to use instead of ~/.netrc to
                             look up login names and passwords for FTP and
                             HTTP sites as well as HTTP proxies.  See ftp(1)
                             for a description of the file format.

     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.

     SSL_ALLOW_SSL3          Allow SSL version 3 when negotiating the
                             connection (not recommended).

     SSL_CA_CERT_FILE        CA certificate bundle containing trusted CA
                             certificates.  Default value: /etc/ssl/cert.pem.

     SSL_CA_CERT_PATH        Path containing trusted CA hashes.

     SSL_CLIENT_CERT_FILE    PEM encoded client certificate/key which will be
                             used in client certificate authentication.

     SSL_CLIENT_KEY_FILE     PEM encoded client key in case key and client
                             certificate are stored separately.

     SSL_CRL_FILE            File containing certificate revocation list.

     SSL_NO_TLS1             Do not allow TLS version 1.0 when negotiating the

     SSL_NO_TLS1_1           Do not allow TLS version 1.1 when negotiating the

     SSL_NO_TLS1_2           Do not allow TLS version 1.2 when negotiating the

     SSL_NO_VERIFY_HOSTNAME  If set, do not verify that the hostname matches
                             the subject of the certificate presented by the

     SSL_NO_VERIFY_PEER      If set, do not verify the peer certificate
                             against trusted CAs.

     To access a proxy server on port 8080, set the
     HTTP_PROXY environment variable in a manner similar to this:


     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:


     The second method is by using the HTTP_PROXY_AUTH environment variable:


     To disable the use of a proxy for an HTTP server running on the local
     host, define NO_PROXY as follows:


     Access HTTPS website without any certificate verification whatsoever:


     Access HTTPS website using client certificate based authentication and a
     private CA:


     fetch(1), ftpio(3), ip(4)

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

     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,

     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 Smorgrav
     <> with numerous suggestions and contributions from Jordan
     K. Hubbard <>, Eugene Skepner <>, Hajimu Umemoto
     <>, Henry Whincup <>, Jukka A. Ukkonen
     <>, Jean-Francois Dockes <>, Michael Gmelin
     <> and others.  It replaces the older ftpio library
     written by Poul-Henning Kamp <> and Jordan K. Hubbard

     This manual page was written by Dag-Erling Smorgrav <> and
     Michael Gmelin <>.

     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

     fetchStatFTP() does not check that the result of an MDTM command is a
     valid date.

     In case password protected keys are used for client certificate based
     authentication the user is prompted for the password on each and every
     fetch operation.

     The man page is incomplete, poorly written and produces badly formatted

     The error reporting mechanism is unsatisfactory.

     Some parts of the code are not fully reentrant.

FreeBSD 11.0-PRERELEASE        November 29, 2015       FreeBSD 11.0-PRERELEASE


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