DACSHTTP(1)

DACS Commands Manual

DACSHTTP(1)

NAME¶

dacshttp - perform an HTTP/HTTPS request

SYNOPSIS¶

dacshttp [-get | -post | -delete | -head | -options | -soptions | -put] [-ll log_level]
[-prompt] [-v] [--version] [[-ct string] | [--content-type string]]
[{-header name value}...] [-headers filename] [-body filename] [-ih]
[-user-agent string] [{-p name value}...] [-proto version-num]
[-proxy proxyhost:proxyport] [-proxymatch hostname[:port] proxyhost:proxyport]
[-f name filename] [{-cookies filename}...] [-ah]
[-ssl command-line] [-ssl-flags flags]
[-u userinfo] [-U proxy-userinfo] uri

DESCRIPTION¶

This program is part of the DACS suite. It is a stand-alone program that neither accepts the usual DACS command line options (dacsoptions[1]) nor accesses any DACS configuration files.

This general-purpose utility sends an HTTP/HTTPS request for uri to a web server and prints the reply to its standard output.

dacshttp will automatically follow redirects according to RFC 2616[2] and up to a compile-time maximum, unless the -prompt flag is given. A non-standard extension is that a redirect to a non-absolute URI is interpreted in a manner compatible with most browsers.

In versions 1.4.27b and earlier, this command was called http.

Note

DACS can issue its own HTTP requests, such as from dacs_authenticate to an external authentication module. This HTTP functionality is provided by the same support code that the dacshttp command uses, and therefore much of the following information applies to these internally generated requests also (e.g., HTTP_PROG[3], SSL_PROG[4], SSL_PROG_ARGS[5], SSL_PROG_CA_CRT[6], SSL_PROG_CLIENT_CRT[7], VFS[8]).

OPTIONS¶

The HTTP GET method is used by default, but some flags implicitly select a different method (e.g., -f and -p). One of the following flags can be used to explicitly specify the HTTP method, provided it is compatible with the other options:

-get

Use the GET method (the default).

-post

Use the POST method.

-head

Use the HEAD method.

-put

Use the PUT method.

-delete

Use the DELETE method.

-options

Use the OPTIONS method.

-soptions

Use the OPTIONS method but ignore anything that follows the authority component of uri and instead use the special case "*" request URI that means that the request applies to the server itself rather than to a particular resource.

These command line flags are also recognized:

-ah

If cookies (credentials) are to be sent (see -cookies), use an Authorization header rather than a Cookie header.

-body filename

Read the message body from filename. It is assumed that the body has already been appropriately formatted for the request's content type.

-cookies filename

Obtain cookies from filename, one per line, to send with the request using the Cookie header. Multiple cookies are separated using a semi-colon, which follows the Netscape spec[9]. Alternatively, multiple cookies can be combined on a single line, separated by either a semi-colon or a comma (following RFC 2109[10], RFC 2965[11] or RFC 6265[12]). This argument may be repeated.

-ct string
--content-type string

Set the Content-Type request-header to string. If the request has an entity-body, the default Content-Type is application/x-www-form-urlencoded; if the request does not have an entity-body, by default the Content-Type request-header is not set.

-f name filename

Passes and encodes the contents of filename as the value for name. By default, the POST method will be used, although PUT and OPTIONS can be selected. If filename is "-", the standard input is read; this form can only be used once on the command line. This argument may be repeated.

-header name value

This flag, which may be repeated, causes the HTTP header name: value to be sent with the request. Neither name nor value are checked in any way.

Note
This will not override headers required or implied by other command line flags, and can result in multiple instances of the same header. For example, the following flags are not equivalent:

-header User-Agent foo
-user-agent foo

The former case will send the User-Agent header twice.

-headers filename

Read additional message headers from filename, one per line, and send them with the request (refer to the -header flag). This flag may be repeated.

-ih

Include the HTTP response headers in the output. They are terminated by a blank line. The status line is labelled "Status-Line".

-ll log_level

Set the debugging output level to log_level (see dacs(1)[13]). The default level is warn, and the -v flag bumps the level to debug or trace.

-p name value

Passes and encodes name=value as part of the entity-body. By default, the POST method will be used, although PUT and OPTIONS can be selected. This argument may be repeated.

-prompt

Prompt the user for permission to proceed after certain events, such as receiving a redirect; the response is affirmative only if it is "yes" or "y". If this option is not specified, the affirmative action will automatically be taken.

-proto version-num

Function in compliance with version-num of the HTTP protocol (e.g., 1.0).

-proxy proxyhost:proxyport

Forward all HTTP requests (except for those that match a -proxymatch flag) to the proxy server at proxyport (a numeric port number or recognized service name) on proxyhost (a domain name or IP address). Proxying is not fully supported by dacshttp, but it will connect to the specified proxy server instead of the server implied by uri.

-proxymatch hostname[:port] proxyhost:proxyport

If hostname matches the host specified in uri, proxy the HTTP request through proxyhost (a domain name or IP address) at proxyport (a numeric port number or recognized service name). If port is not given, it is assumed to be 80 (for the http scheme) or 443 (for the https scheme). Matching is done by resolving hostname to an IP address (if necessary) and comparing it to the effective IP address that is specified by uri. This flag is given priority over the -proxy flag, so it can be used to override a default proxy server.

Note
This option is not implemented. The SSL/TLS flags apply to all connections; this is probably a bug.

-ssl command-line

This flag indicates that HTTPS (i.e, HTTP over an SSL/TLS connection) is to be used, regardless of the scheme specified by uri. Because dacshttp does not directly include SSL/TLS functionality, it uses pipes to communicate with an external program that provides the SSL/TLS connection. The sslclient(1)[14] command is strongly recommended for this purpose (version 3.26 of stunnel(1) and stunnel3, which comes with some releases of stunnel-4.x, might also work).

The command-line is a complete shell command line that will be used to run the program as a filter. For example, this argument might look like either of:

-ssl "/usr/local/dacs/bin/sslclient example.com:443"
-ssl "/usr/local/bin/stunnel -c -r example.com:443"

If the -ssl argument is absent but the uri argument uses the https scheme, dacshttp will still try to use SSL/TLS. It will attempt to use sslclient(1)[14] and assume it is in its default location. If the -ssl argument is present but specifies only one string, that string is assumed to be the path to sslclient(1)[14]. The first example below will run sslclient(1)[14] from /tmp/sslclient to connect to port 443 at example.com; the second example has the same effect but will run sslclient(1)[14] from its default location:

% dacshttp -ssl "/tmp/sslclient" https://example.com
% dacshttp https://example.com

-ssl-flags flags

If SSL/TLS operation is enabled but the -ssl flag is absent or did not simply specify a pathname, append flags to the list of arguments to be passed to the external SSL/TLS provider; when the -ssl flag specifies more than one argument, this flag is ignored. The flags string is a space-separated list of arguments. This flag may be repeated.

For example, in this example dacshttp will invoke sslclient with the two arguments -sm and bobo.example.com:

% dacshttp -ssl-flags "-sm bobo.example.com" https://example.com

If a wildcard server certificate is used, it may be necessary to explicitly match all hosts within a specific domain:

% dacshttp -ssl-flags "-sm .*\.example\.com" https://example.com

Important
When called by dacshttp, error messages produced by sslclient may be lost. If you encounter problems with SSL/TLS operation, work with sslclient(1)[14] to ensure that an SSL/TLS connection can be established, or to determine and resolve the problem. If you discover that sslclient requires command line flags for proper operation, you will need to make sure that dacshttp passes those flags to it.

-user-agent string

Set the User-Agent request-header to string. If not provided, this string will have the prefix "DACS-http/", followed by a DACS release identifier (example: "DACS-http/1.4.1").

-u userinfo
--user userinfo

Send an Authorization header conforming to the HTTP Basic Authentication scheme (RFC 2617[15]). The userinfo consists of a username followed by a colon followed by the user's password. Since the password will be visible, use this flag with caution.

-U proxy-userinfo
--proxyuser proxy-userinfo

Send a Proxy-Authorization header conforming to the HTTP Basic Authentication scheme (RFC 2617[15]). The proxy-userinfo consists of a username, a colon, and then a password for the proxy server. Since the password will be visible, use this flag with caution.

-v

Increase the level of debugging output. This will cause response headers to be displayed, for example. The flag may be repeated.

--version

Print version information to stderr, then exit immediately.

The uri argument is the URL to invoke. It may include a query string suffix (even if HTTP POST is selected). Though not recommended because it is not secure, the uri may include a userinfo component (RFC 2617[15]).

It is an error to attempt to send more than one Authorization header.

Whether selected implicitly or explicitly, the command line must specify exactly one of the HTTP methods.

Request headers specified using the -header or -headers flags are sent in the order in which the flags appear on the command line. If they are read from a file, there ordering is maintained.

EXAMPLES¶

The following will retrieve RFC 2616[2] and save it in rfc2616.txt:

% dacshttp "http://www.rfc-editor.org/rfc/rfc2616.txt" > rfc2616.txt

This will do a GET on the given URL, passing the query string foo=baz, and writing the result to stdout:

% dacshttp "https://example.com/cgi-bin/dacs/dacs_prenv?foo=baz"

This will do a POST on the given URL, passing two arguments:

% dacshttp -p foo baz -p bar zork https://example.com/cgi-bin/dacs/dacs_prenv

This will make an HTTP GET method request over SSL/TLS to the given URL:

% dacshttp -ssl "/usr/local/dacs/bin/sslclient example.com:443" \
    https://example.com/cgi-bin/dacs/dacs_prenv

These two commands are equivalent. They submit a request associated with username julia and password herpasswd, which causes an Authorization header conforming to the HTTP Basic Authentication scheme (RFC 2617[15]) to be sent:

% dacshttp http://julia:herpasswd@example.com
% dacshttp -u julia:herpasswd http://example.com

DIAGNOSTICS¶

The program exits 0 if everything was fine, 1 if an error occurred.

BUGS¶

It can sometimes be a useful tool, but this program's primary purpose is for developing and testing DACS core functionality. There are many readily-available and better HTTP clients.

Use of an SSL/TLS provider other than sslclient(1)[14] is officially deprecated. dacshttp should not require an external program to provide SSL/TLS functionality. Recent development makes it doubtful that any other program will function properly with dacshttp.

dacshttp is only a partial implementation of RFC 2616[2]. It only talks HTTP (no other URI schemes are supported). Received cookies are discarded. Authentication via RFC 2617[15] is only partially implemented: a single username and password to authenticate the user submitting the request and/or a single username and password to gain access to a proxy server can be specified to be sent with the request. No client-side caching of any kind is performed.