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API Reference

Anvil provides an API that is meant to be used by programs launched from within Anvil. The API is accessed over HTTP and interacts in a REST manner. It is available to both local and remote programs; for remote programs it is tunneled through the SSH session.


To use the API, programs must read the ANVIL_API_PORT environment variable and open a TCP connection to the API to the local host on that port.

Once connected the program can perform HTTP requests.


Each request from the program must contain the HTTP header Anvil-Sess which must be set to the value of the environment variable ANVIL_API_SESS.


The contents of requests and responses may be encoded as JSON or CSV. To choose the encoding, the program should set the Content-Type and Accept headers to application/json or text/csv. Some responses from Anvil are always returned in the encoding text/plain regardless of the Accept header that the program set, such as a response containing the contents of a window body.


The following operations are supported by the API. In the table the number 1 is a placeholder used to represent a window id, and may be replaced with any window id value.

Method URL Behaviour Structure
GET /wins/ list window ids and paths array of structures with fields Id, GlobalPath, Path
POST /wins/ create a new window and return the id structure with field Id
GET /wins/1/body Get contents of body of window 1 unstructured plain text
PUT /wins/1/body Set contents of body of window 1 unstructured plain text
POST /wins/1/body Append to the contents of the body of window 1 unstructured plain text
GET /wins/1/body/info Get info about window body (i.e. length) structure with field Len, the number of UTF-8 characters in the window body
GET /wins/1/body/cursors Get info about cursors in the window body array of integers. Each element represents the position of a cursor as an offset of the number of UTF-8 characters from the beginning of the file
PUT /wins/1/body/cursors Set position of cursors in the window body array of integers. The semantics are the same as GET.
GET /wins/1/info get window information, such as file paths structure with fields Id, GlobalPath, Path
GET /wins/1/selections get window selections array of structures with fields Start, End, Len
GET /wins/1/tag Get the tag of window 1 unstructured plain text
PUT /wins/1/tag Set the tag of window 1 unstructured plain text
GET /jobs List the running jobs array of structures with the field Name
POST /execute Execute a command as if it was clicked. The command is executed as if it was run from the editor tag a structure with the fields Cmd, Args. Args is an array of strings
GET /notifs Get any pending notifications for the current API session. The notifications are then cleared. array of structures with fields WinId, Op, Offset, Len, Cmd. The Op field describes the type of operation: 0 is an insert to the body of window with id WinId at Offset of length Len; 1 is a delete in the body of the window with id WinId of length -Len; and 2 is the execution of the command Cmd that was executed from the window with id WinId. Only the commands registered by the program using the /cmds URL are notified.
POST /cmds Create a new client-defined command. If it already exists, register interest in it. an array of strings where each element is a command name that does not contain spaces.

Sample Program

This section contains an example program which uses the Anvil API. It is a shell script which formats C code and uses the CSV encoding when communicating with Anvil through the API.

To use it, execute it from the tag or body of a window containing C source code. If there is no selection, the entire file is formatted. If there is a selection only that section of the file is formatted.

The program demonstrates that extending Anvil through its API can be done as simply as writing a shell script.

#!/usr/bin/env bash

# Run clang-format on selected parts of text in an Anvil window body.



# Get the selections of the current window in CSV format and strip off the CSV header line.
selections=`curl -s -H 'Accept: text/csv' -H "Anvil-Sess: $ANVIL_API_SESS" http://localhost:$ANVIL_API_PORT/wins/$ANVIL_WIN_ID/selections | tail -n +2`
if [ "$selections" != "" ]
  for sel in $selections
    offset=`echo $sel | cut -d, -f1,1`
    length=`echo $sel | cut -d, -f3,3`

    clang_parts="$clang_parts -offset $offset -length $length"

# Get contents of window, pipe it through clang-format, then put the result back into the window.

curl -s -H "Anvil-Sess: $ANVIL_API_SESS" http://localhost:$ANVIL_API_PORT/wins/$ANVIL_WIN_ID/body | \
  clang-format -style="{BasedOnStyle: $BASE_STYLE, IndentWidth: 4, ColumnLimit: 0}" $clang_parts | \
  curl -X PUT -s -H "Anvil-Sess: $ANVIL_API_SESS" --data-binary @- http://localhost:$ANVIL_API_PORT/wins/$ANVIL_WIN_ID/body