maxBuffer

maxBuffer is an option in Node.js that governs how much data a child process’s stdout and stderr can buffer in memory. It is part of the child_process module and applies to commands run with exec and execFile. The default value is 1024 * 1024 bytes (1 MB). If the combined output from stdout and stderr exceeds this limit, the child process is terminated and an error is returned indicating that the maxBuffer was exceeded. This feature helps prevent unbounded memory usage when a spawned process produces large amounts of output.

The maxBuffer limit applies to the total buffered data from both streams. If the limit is reached before the child process finishes, the remaining output may be discarded and an error is produced. Users may increase the limit when they anticipate large output, or switch to streaming execution with spawn, which provides separate, real-time streams and does not buffer all output in memory.

Common usage involves passing an options object to exec or execFile with a maxBuffer property, for example to allow up to 10 MB of output. When choosing a value, developers should balance the need to accommodate large outputs against memory usage, particularly in applications that run many child processes concurrently. For completely unbuffered streaming, using spawn and handling the data as it arrives is recommended.

See also: child_process module, exec, execFile, spawn.