45 lines
2.0 KiB
Markdown
45 lines
2.0 KiB
Markdown
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<!-- Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. -->
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<!-- SPDX-License-Identifier: curl -->
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# VARIABLES
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curl supports command line variables (added in 8.3.0). Set variables with
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--variable name=content or --variable name@file (where `file` can be stdin if
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set to a single dash (-)).
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Variable contents can be expanded in option parameters using `{{name}}` if the
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option name is prefixed with `--expand-`. This gets the contents of the
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variable `name` inserted, or a blank if the name does not exist as a
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variable. Insert `{{` verbatim in the string by prefixing it with a backslash,
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like `\{{`.
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You an access and expand environment variables by first importing them. You
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can select to either require the environment variable to be set or you can
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provide a default value in case it is not already set. Plain --variable %name
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imports the variable called 'name' but exits with an error if that environment
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variable is not already set. To provide a default value if it is not set, use
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--variable %name=content or --variable %name@content.
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Example. Get the USER environment variable into the URL, fail if USER is not
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set:
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--variable '%USER'
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--expand-url = "https://example.com/api/{{USER}}/method"
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When expanding variables, curl supports a set of functions that can make the
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variable contents more convenient to use. It can trim leading and trailing
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white space with `trim`, it can output the contents as a JSON quoted string
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with `json`, URL encode the string with `url` or base64 encode it with `b64`.
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To apply functions to a variable expansion, add them colon separated to the
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right side of the variable. Variable content holding null bytes that are not
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encoded when expanded cause error.
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Example: get the contents of a file called $HOME/.secret into a variable
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called "fix". Make sure that the content is trimmed and percent-encoded when
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sent as POST data:
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--variable %HOME
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--expand-variable fix@{{HOME}}/.secret
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--expand-data "{{fix:trim:url}}"
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https://example.com/
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Command line variables and expansions were added in 8.3.0.
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