curl/docs/cmdline-opts/variable.md

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c: Copyright (C) Daniel Stenberg, daniel@haxx.se, et al. SPDX-License-Identifier: curl Long: variable Arg: <[%]name=text/@file> Help: Set variable Category: curl Added: 8.3.0 Multi: append See-also:

• config Example:
• --variable name=smith --expand-url "$URL/{{name}}" ---

--variable

Set a variable with name=content or name@file (where file can be stdin if set to a single dash (-)). The name is a case sensitive identifier that must consist of no other letters than a-z, A-Z, 0-9 or underscore. The specified content is then associated with this identifier.

Setting the same variable name again overwrites the old contents with the new.

The contents of a variable can be referenced in a later command line option when that option name is prefixed with --expand-, and the name is used as {{name}}.

--variable can import environment variables into the name space. Opt to either require the environment variable to be set or provide a default value for the variable in case it is not already set.

--variable %name imports the variable called name but exits with an error if that environment variable is not already set. To provide a default value if the environment variable is not set, use --variable %name=content or --variable %name@content. Note that on some systems - but not all - environment variables are case insensitive.

Added in curl 8.12.0: when getting contents from a file, you can request to get a byte range from it by appending ";[start-end]" to the filename, where start and end are byte offsets to include from the file. For example, asking for offset "2-10" means offset two to offset ten, including the byte offset 10, meaning 9 bytes in total. "2-2" means a single byte at offset 2. Not providing a second number implies to the end of the file. The start offset cannot be larger than the end offset. Asking for a range that is outside of the file size makes the variable contents empty.

To assign a variable using contents from another variable, use --expand-variable. Like for example assigning a new variable using contents from two other:

curl --expand-variable "user={{firstname}} {{lastname}}"

When expanding variables, curl supports a set of functions that can make the variable contents more convenient to use. You apply a function to a variable expansion by adding a colon and then list the desired functions in a comma-separated list that is evaluated in a left-to-right order. Variable content holding null bytes that are not encoded when expanded, causes an error.

Available functions:

trim

removes all leading and trailing white space.

Example:

curl --expand-url https.//example.com/{{url:trim}}

json

outputs the content using JSON string quoting rules.

Example:

curl --expand-data {{data:json}} https://example.com

url

shows the content URL (percent) encoded.

Example:

curl --expand-url https://example.com/{{path:url}}

b64

expands the variable base64 encoded

Example:

curl --expand-url https://example.com/{{var:b64}}