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FETCH (3) | C library functions | Unix Manual Pages | :man


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 Scheme
Ftp Scheme
Http Scheme
Return Values
See Also


.Lb libfetch


.In sys/param.h
.In stdio.h
.In 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:

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
.Vt url structure, which is defined as follows in
.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];
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 lower-level functions to perform the actual transfer. fetchXGetURL also returns the remote document’s metadata in the
.Vt 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
.Vt url_stat structure is defined as follows in
.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
.Vt url_ent structures. The
.Vt url_ent structure is defined as follows in
.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
.Vt 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 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.


Apart from setting the appropriate environment variables and specifying the user name and password in the URL or the
.Vt 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
.Vt 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
.Vt 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
.In fetch.h :

Operation aborted
Authentication failed
Service unavailable
File exists
File system full
Informational response
Insufficient memory
File has moved
Network error
No error
Protocol error
Resolver error
Server error
Temporary error
Operation timed out
File is not available
Unknown error
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 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.


To access a proxy server on proxy.example.com 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:


fetch(1), ftpio(3), ip(4)
.Rs How to Use Anonymous FTP
.Rs Uniform Resource Locators (URL)




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