useExec

Hook that executes a command and returns the AsyncState corresponding to the execution of the command.

It follows the stale-while-revalidate cache invalidation strategy popularized by HTTP RFC 5861. useExec first returns the data from cache (stale), then executes the command (revalidate), and finally comes with the up-to-date data again.

The last value will be kept between command runs.

Signature

There are two ways to use the hook.

The first one should be preferred when executing a single file. The file and its arguments don't have to be escaped.

function useExec<T, U>(
  file: string,
  arguments: string[],
  options?: {
    shell?: boolean | string;
    stripFinalNewline?: boolean;
    cwd?: string;
    env?: NodeJS.ProcessEnv;
    encoding?: BufferEncoding | "buffer";
    input?: string | Buffer;
    timeout?: number;
    parseOutput?: ParseExecOutputHandler<T>;
    initialData?: U;
    keepPreviousData?: boolean;
    execute?: boolean;
    onError?: (error: Error) => void;
    onData?: (data: T) => void;
    onWillExecute?: (args: string[]) -> void;
  }
): AsyncState<T> & {
  revalidate: () => void;
  mutate: MutatePromise<T | U | undefined>;
};

The second one can be used to execute more complex commands. The file and arguments are specified in a single command string. For example, useExec('echo', ['Raycast']) is the same as useExec('echo Raycast').

If the file or an argument contains spaces, they must be escaped with backslashes. This matters especially if command is not a constant but a variable, for example with environment.supportPath or process.cwd(). Except for spaces, no escaping/quoting is needed.

The shell option must be used if the command uses shell-specific features (for example, && or ||), as opposed to being a simple file followed by its arguments.

function useExec<T, U>(
  command: string,
  options?: {
    shell?: boolean | string;
    stripFinalNewline?: boolean;
    cwd?: string;
    env?: NodeJS.ProcessEnv;
    encoding?: BufferEncoding | "buffer";
    input?: string | Buffer;
    timeout?: number;
    parseOutput?: ParseExecOutputHandler<T>;
    initialData?: U;
    keepPreviousData?: boolean;
    execute?: boolean;
    onError?: (error: Error) => void;
    onData?: (data: T) => void;
    onWillExecute?: (args: string[]) -> void;
  }
): AsyncState<T> & {
  revalidate: () => void;
  mutate: MutatePromise<T | U | undefined>;
};

Arguments

• file is the path to the file to execute.

• arguments is an array of strings to pass as arguments to the file.

or

• command is the string to execute.

With a few options:

• options.shell is a boolean or a string to tell whether to run the command inside of a shell or not. If true, uses /bin/sh. A different shell can be specified as a string. The shell should understand the -c switch.

  We recommend against using this option since it is:

  • not cross-platform, encouraging shell-specific syntax.

  • slower, because of the additional shell interpretation.

  • unsafe, potentially allowing command injection.

• options.stripFinalNewline is a boolean to tell the hook to strip the final newline character from the output. By default, it will.

• options.cwd is a string to specify the current working directory of the child process. By default, it will be process.cwd().

• options.env is a key-value pairs to set as the environment of the child process. It will extend automatically from process.env.

• options.encoding is a string to specify the character encoding used to decode the stdout and stderr output. If set to "buffer", then stdout and stderr will be a Buffer instead of a string.

• options.input is a string or a Buffer to write to the stdin of the file.

• options.timeout is a number. If greater than 0, the parent will send the signal SIGTERM if the child runs longer than timeout milliseconds. By default, the execution will timeout after 10000ms (eg. 10s).

• options.parseOutput is a function that accepts the output of the child process as an argument and returns the data the hooks will return - see ParseExecOutputHandler. By default, the hook will return stdout.

Including the useCachedPromise's options:

• options.keepPreviousData is a boolean to tell the hook to keep the previous results instead of returning the initial value if there aren't any in the cache for the new arguments. This is particularly useful when used for data for a List to avoid flickering. See Argument dependent on user input for more information.

Including the useCachedState's options:

• options.initialData is the initial value of the state if there aren't any in the Cache yet.

Including the usePromise's options:

• options.execute is a boolean to indicate whether to actually execute the function or not. This is useful for cases where one of the function's arguments depends on something that might not be available right away (for example, depends on some user inputs). Because React requires every hook to be defined on the render, this flag enables you to define the hook right away but wait until you have all the arguments ready to execute the function.

• options.onError is a function called when an execution fails. By default, it will log the error and show a generic failure toast with an action to retry.

• options.onData is a function called when an execution succeeds.

• options.onWillExecute is a function called when an execution will start.

Return

Returns an object with the AsyncState corresponding to the execution of the command as well as a couple of methods to manipulate it.

• data, error, isLoading - see AsyncState.

• revalidate is a method to manually call the function with the same arguments again.

• mutate is a method to wrap an asynchronous update and gives some control over how the useFetch's data should be updated while the update is going through. By default, the data will be revalidated (eg. the function will be called again) after the update is done. See Mutation and Optimistic Updates for more information.

Example

import { List } from "@raycast/api";
import { useExec } from "@raycast/utils";
import { cpus } from "os";
import { useMemo } from "react";

const brewPath = cpus()[0].model.includes("Apple") ? "/opt/homebrew/bin/brew" : "/usr/local/bin/brew";

export default function Command() {
  const { isLoading, data } = useExec(brewPath, ["info", "--json=v2", "--installed"]);
  const results = useMemo<{ id: string; name: string }[]>(() => JSON.parse(data || "{}").formulae || [], [data]);

  return (
    <List isLoading={isLoading}>
      {results.map((item) => (
        <List.Item key={item.id} title={item.name} />
      ))}
    </List>
  );
}

Argument dependent on user input

By default, when an argument passed to the hook changes, the function will be executed again and the cache's value for those arguments will be returned immediately. This means that in the case of new arguments that haven't been used yet, the initial data will be returned.

This behaviour can cause some flickering (initial data -> fetched data -> arguments change -> initial data -> fetched data, etc.). To avoid that, we can set keepPreviousData to true and the hook will keep the latest fetched data if the cache is empty for the new arguments (initial data -> fetched data -> arguments change -> fetched data).

import { useState } from "react";
import { Detail, ActionPanel, Action } from "@raycast/api";
import { useFetch } from "@raycast/utils";

export default function Command() {
  const [searchText, setSearchText] = useState("");
  const { isLoading, data } = useExec("brew", ["info", searchText]);

  return <Detail isLoading={isLoading} markdown={data} />;
}

When passing a user input to a command, be very careful about using the shell option as it could be potentially dangerous.

Mutation and Optimistic Updates

In an optimistic update, the UI behaves as though a change was successfully completed before receiving confirmation from the server that it was - it is being optimistic that it will eventually get the confirmation rather than an error. This allows for a more responsive user experience.

You can specify an optimisticUpdate function to mutate the data in order to reflect the change introduced by the asynchronous update.

When doing so, you can specify a rollbackOnError function to mutate back the data if the asynchronous update fails. If not specified, the data will be automatically rolled back to its previous value (before the optimistic update).

import { Detail, ActionPanel, Action, showToast, Toast } from "@raycast/api";
import { useFetch } from "@raycast/utils";

export default function Command() {
  const { isLoading, data, revalidate } = useExec("brew", ["info", "--json=v2", "--installed"]);
  const results = useMemo<{}[]>(() => JSON.parse(data || "[]"), [data]);

  const installFoo = async () => {
    const toast = await showToast({ style: Toast.Style.Animated, title: "Installing Foo" });
    try {
      await mutate(
        // we are calling an API to do something
        installBrewCask("foo"),
        {
          // but we are going to do it on our local data right away,
          // without waiting for the call to return
          optimisticUpdate(data) {
            return data?.concat({ name: "foo", id: "foo" });
          },
        },
      );
      // yay, the API call worked!
      toast.style = Toast.Style.Success;
      toast.title = "Foo installed";
    } catch (err) {
      // oh, the API call didn't work :(
      // the data will automatically be rolled back to its previous value
      toast.style = Toast.Style.Failure;
      toast.title = "Could not install Foo";
      toast.message = err.message;
    }
  };

  return (
    <List isLoading={isLoading}>
      {(data || []).map((item) => (
        <List.Item
          key={item.id}
          title={item.name}
          actions={
            <ActionPanel>
              <Action title="Install Foo" onAction={() => installFoo()} />
            </ActionPanel>
          }
        />
      ))}
    </List>
  );
}

Types

AsyncState

An object corresponding to the execution state of the function.

// Initial State
{
  isLoading: true, // or `false` if `options.execute` is `false`
  data: undefined,
  error: undefined
}

// Success State
{
  isLoading: false,
  data: T,
  error: undefined
}

// Error State
{
  isLoading: false,
  data: undefined,
  error: Error
}

// Reloading State
{
  isLoading: true,
  data: T | undefined,
  error: Error | undefined
}

MutatePromise

A method to wrap an asynchronous update and gives some control about how the useFetch's data should be updated while the update is going through.

export type MutatePromise<T> = (
  asyncUpdate?: Promise<any>,
  options?: {
    optimisticUpdate?: (data: T) => T;
    rollbackOnError?: boolean | ((data: T) => T);
    shouldRevalidateAfter?: boolean;
  },
) => Promise<any>;

ParseExecOutputHandler

A function that accepts the output of the child process as an argument and returns the data the hooks will return.

export type ParseExecOutputHandler<T> = (args: {
  /** The output of the process on stdout. */
  stdout: string | Buffer; // depends on the encoding option
  /** The output of the process on stderr. */
  stderr: string | Buffer; // depends on the encoding option
  error?: Error | undefined;
  /** The numeric exit code of the process that was run. */
  exitCode: number | null;
  /** The name of the signal that was used to terminate the process. For example, SIGFPE. */
  signal: NodeJS.Signals | null;
  /** Whether the process timed out. */
  timedOut: boolean;
  /** The command that was run, for logging purposes. */
  command: string;
  /** The options passed to the child process, for logging purposes. */
  options?: ExecOptions | undefined;
}) => T;