Local Interactive Execution Probe

Execute a command in a local shell and interact with it.

Identification and Properties

Probe Type ID: exec.interactive


Name Type Default value Description
separator string None Should we notify only complete lines (or whatever) based on this separator ?
timeout float 0.5 Maximum amount of time to wait for new data before notifying of it, when no separator is used
encoding string 'utf-8' The encoding to use to turn the output into unicode (also used to encode data sent to the started process)


This probe enables to execute a shell-based program interactively, i.e. start a program, be notified of what it outputs to standard output (stdout, stderr), send it some input or signals.

Output can be notified on a per-line basis (or any separator - the separator is not included in the event sent back to the userland) or a timeout basis (useful if the program does not outputs lines only, for instance prompts).

This probe does not require the started program to use unbuffered stdout.

Typical use cases include:

  • CLI testing
  • Program output watching, for instance something that can dump real-time traces to stdout, avoiding the use of combined exec (that executes a blocking program whose output is redirected to a temp file) and file.watcher (that watches the temp file created by the program we should watch the output from) probes.

Basically you just specify a command to start that will be executed within a shell, providing an optional list of regular expressions the output must match before being sent to userland (a egrep equivalent).[[BR]] Whenever you output to stdout/stderr is detected, based on separator and timeout properties, it checks that it matches at least one of the regular expressions provided above before enqueing a OutputNotification message to userland. If the matched regular expression contains named groups, corresponding fields are automatically added in this message (as for the ProbeFileWatcher).

At any time, you may send some input to the started process using the input choice of the InteractiveExecCommand message (don’t forget possible trailing carriage returns, as they are not sent automatically) or send a signal using its POSIX integer value and the signal choice of the InteractiveExecCommand message.

When the process is over (for whatever reason), a ExecStatus message is enqueued, containing the execution status as a shell executing the command would have provided.


  • stderr output is currently reported within the stdout stream
  • interleaved stdout/stderr output are not garanteed to be delivered in the correct order


All POSIX platforms. Windows platforms are not supported.



See Also

TTCN-3 Types Equivalence

The test system interface port bound to such a probe complies with the InteractiveExecPortType port type as specified below:

type union InteractiveExecCommand
  StartCommand start,
  universal charstring input,
  integer signal,

type record StartCommand
  charstring command,
  record of charstring patterns optional, // defaulted to [ r'.*' ]

type record OutputNotification
  universal charstring output,
  universal charstring matched_*,
  charstring stream, // 'stderr' or 'stdout'

type record ExecStatus
  integer status,

type port InteractiveExecPortType message
  in  InteractiveExecCommand;
  out ExecStatus, OutputNotification;