Использование параметров в скрипте bash с помощью curl

в чем проблема?

вы должны использовать двойные кавычки.

Shellcheck проанализирует ваш скрипт и поищет ошибки:

$ shellcheck myscript

Line 1:
random="$(cat something.txt)"
^-- SC2148: Tips depend on target shell and yours is unknown. Add a shebang.

Line 3:
url="$(curl -i -L -X POST --cookie 'info=' \
^-- SC2034: url appears unused. Verify use (or export if used externally).
                                   ^-- SC2016: Expressions don't expand in single quotes, use double quotes for that.

Line 4:
  -F 'var=' \
     ^-- SC2016: Expressions don't expand in single quotes, use double quotes for that.

Line 6:
  -F 'file[]=@' \
     ^-- SC2016: Expressions don't expand in single quotes, use double quotes for that.

Line 7:
   https://example.com/upload?id=${random})"
                                 ^-- SC2086: Double quote to prevent globbing and word splitting.

$