un-nest curl

curl-8.15.0/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: you can get a byte range from the source by appending
+`[start-end]` to the variable name, where *start* and *end* are byte offsets
+to include from the contents. For example, asking for offset "2-10" means
+offset two to offset ten, inclusive, resulting in 9 bytes in total. `2-2`
+means a single byte at offset 2. Not providing a second number implies to the
+end of data. 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.
+For example, getting the first one hundred bytes from a given file:
+
+    curl --variable "fraction[0-99]@filename"
+
+Given a byte range that has no data results in an empty string. Asking for a
+range that is larger than the content makes curl use the piece of the data
+that exists.
+
+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/{{var: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}}
+
+## `64dec`
+
+decodes a base64 encoded character sequence. If the sequence is not possible
+to decode, it instead outputs `[64dec-fail]`
+
+Example:
+
+    curl --expand-url https://example.com/{{var:64dec}}
+
+(Added in 8.13.0)