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 access and expand environment variables by first importing them. You 15select to either require the environment variable to be set or you can provide 16a 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
