form_field - Linux


form_field manipulates form fields in multi-part forms. It can get/set specific fields and headers in a multi-part form, simplifying interaction with complex form data.


form_field [-a] [-d] [-i FORMAT] [-o FORMAT] [-p PARAM] [-r PARAM] [-s SEPARATOR] [-t PARAM] FILE...


  • -a: (append) Append to existing forms.
  • -d: (delete) Delete specified field(s).
  • -i FORMAT: (in) Input format (defaults to "autodetect").
  • -o FORMAT: (out) Output format (defaults to "autodetect").
  • -p PARAM: (put) Set specified field(s) to value.
  • -r PARAM: (replace) Replace specified header(s) with value.
  • -s SEPARATOR: (separator) Header-value separator (defaults to "=").
  • -t PARAM: (truncate) Truncate specified header(s).


Get field value

form_field -i multipart file.txt -p 'name=John'

Set field value

form_field -i multipart file.txt -a -p 'name=Jane'

Delete field

form_field -i multipart file.txt -d 'name=John'

Replace header

form_field -r 'Content-Type=multipart/form-data' file.txt

Common Issues

  • Incorrect input format: Ensure the input file is a valid multi-part form.
  • Duplicate field names: When appending to existing forms, field names must be unique.
  • Empty output: Check that the output format is compatible with the desired output.


form_field can be combined with:

  • curl: Interact with web forms interactively.
  • wget: Download multi-part form responses.
  • sed: Manipulate form data using text-based commands.

Related Commands

  • multipart: Manipulate multi-part forms from the command line.
  • httpie: HTTP client with form data support.