shell.md

💻 Shell

Avoiding shells

In general, shells should be avoided because they are:

• Not cross-platform, encouraging shell-specific syntax.
• Slower, because of the additional shell interpretation.
• Unsafe, potentially allowing command injection (see the escaping section).

In almost all cases, plain JavaScript is a better alternative to shells. The following page shows how to convert Bash into JavaScript.

When a shell is not needed

On Windows, a shell is often used to work around limitations of the OS. This is not needed with Execa. In particular, shell: true is not required to:

• run .cmd and .bat files, such as npm.cmd
• resolve a command by name using PATHEXT
• run shebang scripts
• escape file paths and arguments

A shell is only needed to use shell-specific syntax, such as pipes |, redirections >, globbing * or environment variable expansion $VAR.

Specific shell

import {execa} from 'execa';

await execa({shell: '/bin/bash'})`npm run "$TASK" && npm run test`;

OS-specific shell

When the shell option is true, sh is used on Unix and cmd.exe is used on Windows.

sh and cmd.exe syntaxes are very different. Therefore, this is usually not useful.

await execa({shell: true})`npm run build`;

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