Scripting 8.1. The sendpraat subroutine

Scripting 8.1. The sendpraat subroutine

Sendpraat can be a subroutine for sending messages to a running Praat program.

C syntax

   sendpraat (void *display, const char *program, long timeOut, char *text);

Arguments

display: this argument is ignored; you can supply NULL.
program: the name of a running program that uses the Praat shell, e.g. "Praat" or "ALS". The first letter may be specified as lower or upper case; it will be converted to upper case for Windows or MacOS and to lower case for Linux.
timeOut (MacOS and Linux only): the number of seconds that sendpraat will wait for an answer before writing an error message. A timeOut of 0 means that the message will be sent asynchronously, i.e., that sendpraat will return immediately without issuing any error message.
text: the script text to be sent. Sendpraat may alter this text!

Example 1: killing a program

   char message [100], *errorMessage;

   strcpy (message, "Quit");

   errorMessage = sendpraat (NULL, "praat", 0, message);

   if (errorMessage) fprintf (stderr, "%s", errorMessage);

This causes the program Praat to quit (gracefully), because Quit is a fixed command in one of the menus of that program. On MacOS and Linux, sendpraat returns immediately; on Windows, the timeOut argument is ignored. The return value errorMessage is a statically allocated string internal to sendpraat, and is overwritten by the next call to sendpraat.

Example 2: playing a sound file in reverse

Suppose you have a sound file whose name is in the variable fileName, and you want the program Praat, which can play sounds, to play this sound backwards.

   char message [1000], *errorMessage;

   snprintf (message,1000, "Read from file: ~%s\nPlay reverse\nRemove", fileName);

   errorMessage = sendpraat (NULL, "praat", 3000, message);

This will work because Play reverse is an action command that becomes available in the dynamic menu when a Sound is selected. On Linux, sendpraat will allow Praat at most 3000 seconds to perform this.

Example 3: executing a large script file

Sometimes, it may be unpractical to send a large script directly to sendpraat. Fortunately, the receiving program knows runScript:

   char message [100], *errorMessage;

   strcpy (message, "runScript: \"doAll.praat\", 20");

   errorMessage = sendpraat (NULL, "praat", 0, message);

This causes the program Praat to run the script doAll.praat with an argument of "20".

How to download

You can download the source code of the sendpraat subroutine via www.praat.org or from http://www.fon.hum.uva.nl/praat/sendpraat.html.

Instead

Instead of using sendpraat, you can also just take the following simple steps in your program:

1. on Linux, write the Praat script that you want to run, and save it as ~/.praat-dir/message;

2. get Praat's process id from ~/.praat-dir/pid;

3. if Praat's process id is e.g. 1178, send it a SIGUSR1 signal: kill -USR1 1178

If the first line of your script is the comment “# 999”, where 999 stands for the process id of your program, Praat will send your program a SIGUSR2 signal back when it finishes handling the script. If you do not want to receive such a message (if your program has no handler for it, the SIGUSR2 signal will kill your program), then do not include such a line.