1<!-- Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. --> 2<!-- SPDX-License-Identifier: curl --> 3# VARIABLES 4curl supports command line variables (added in 8.3.0). Set variables with 5--variable name=content or --variable name@file (where `file` can be stdin if 6set to a single dash (-)). 7 8Variable contents can be expanded in option parameters using `{{name}}` if the 9option name is prefixed with `--expand-`. This gets the contents of the 10variable `name` inserted, or a blank if the name does not exist as a 11variable. Insert `{{` verbatim in the string by prefixing it with a backslash, 12like `\{{`. 13 14You an access and expand environment variables by first importing them. You 15can select to either require the environment variable to be set or you can 16provide a default value in case it is not already set. Plain --variable %name 17imports the variable called 'name' but exits with an error if that environment 18variable is not already set. To provide a default value if it is not set, use 19--variable %name=content or --variable %name@content. 20 21Example. Get the USER environment variable into the URL, fail if USER is not 22set: 23 24 --variable '%USER' 25 --expand-url = "https://example.com/api/{{USER}}/method" 26 27When expanding variables, curl supports a set of functions that can make the 28variable contents more convenient to use. It can trim leading and trailing 29white space with `trim`, it can output the contents as a JSON quoted string 30with `json`, URL encode the string with `url` or base64 encode it with `b64`. 31To apply functions to a variable expansion, add them colon separated to the 32right side of the variable. Variable content holding null bytes that are not 33encoded when expanded cause error. 34 35Example: get the contents of a file called $HOME/.secret into a variable 36called "fix". Make sure that the content is trimmed and percent-encoded when 37sent as POST data: 38 39 --variable %HOME 40 --expand-variable fix@{{HOME}}/.secret 41 --expand-data "{{fix:trim:url}}" 42 https://example.com/ 43 44Command line variables and expansions were added in 8.3.0. 45
