std.process

Functions for starting and interacting with other processes, and for working with the current process' execution environment.

Process_handling:

• spawnProcess spawns a new process, optionally assigning it an

  arbitrary set of standard input, output, and error streams. The function returns immediately, leaving the child process to execute in parallel with its parent. All other functions in this module that spawn processes are built around spawnProcess.

• wait makes the parent process wait for a child process to

  terminate. In general one should always do this, to avoid child processes becoming "zombies" when the parent process exits. Scope guards are perfect for this – see the spawnProcess documentation for examples. tryWait is similar to wait, but does not block if the process has not yet terminated.

• pipeProcess also spawns a child process which runs

  in parallel with its parent. However, instead of taking arbitrary streams, it automatically creates a set of pipes that allow the parent to communicate with the child through the child's standard input, output, and/or error streams. This function corresponds roughly to C's popen function.

• execute starts a new process and waits for it

  to complete before returning. Additionally, it captures the process' standard output and error streams and returns the output of these as a string.

• spawnShell, pipeShell and executeShell work like

  spawnProcess, pipeProcess and execute, respectively, except that they take a single command string and run it through the current user's default command interpreter. executeShell corresponds roughly to C's system function.

• kill attempts to terminate a running process.

The following table compactly summarises the different process creation functions and how they relate to each other:

Other_functionality:

• pipe is used to create unidirectional pipes.
• environment is an interface through which the current process'

  environment variables can be read and manipulated.

• escapeShellCommand and escapeShellFileName are useful

  for constructing shell command lines in a portable way.