How to write to a file during execution

• version

  1.1.1

• scope

  Example.

  This code is provided as example code for a user to base their code on.

• description

  How to write to a file during execution

• boards

  Unless otherwise specified, this example runs on the SliceKIT Core Board, but can easily be run on any XMOS device by using a different XN file.

The xTIMEcomposer tools can handle system calls on behalf of the target application. This handling is enabled by default.

A file can be opened for writing as follows:

int fd = _open("test.txt", O_WRONLY | O_CREAT | O_TRUNC, S_IREAD | S_IWRITE);
if (fd == -1) {
  printstrln("Error: _open failed");
  exit(1);
}

An open file can be written using the _write system call

if (_write(fd, "hello there!", 13) != 13) {
  printstrln("Error: _write failed");
  exit(1);
}

We can then close an open file using the _close system call

  if (_close(fd) != 0) {
    printstrln("Error: _close failed.");
    exit(1);
  }
  return 0;
}

Compile the above code. When the resulting executable is run, a file called test.txt containing ‘hello world!’ is written to the current working directory.

Note: In this case we are using the raw system call functions directory as we are working in XC. However, if working in C then it might be advisable to the the C std library equivalents: fopen, fwrite and fclose.