Как прочитать строку из текстового файла с помощью CAPL?

Проверьте fileGetString. Ниже приведен пример кода в меню справки CAPL.

variables
{
msTimer writeTimer;
long glbPeriod = 250;

dword glbHandle = 0;
long glbValue;
}

on Start
{
char buffer[64];
long ret;

//
// Opens the file in ASCII mode for read access.
//
// To determine the absolute path, the search procedure will be used.
// The file must be located in the directory of the databases or the
// configuration directory.
//
glbHandle = OpenFileRead ("Data.Txt",0);

if ( glbHandle!=0 )
{
//
// got to end of file ...
//
while ( fileGetString(buffer,elcount(buffer),glbHandle)!=0 ) {};
//
// Get the last parameters
// (saved on disk after the end the last measurement)
//
glbValue = atol (buffer);
write ("Last value %d.",glbValue);
fileClose (glbHandle);
}
else
{
write ("File 'Data.Txt' was not opened for read access.");
}
//
// Open the file in ASCII mode for write access.
//
// The write path was not set using the function setWritePath(), so
// the configuration directory will be used instead. This is the
// default behavior.
//
glbHandle = OpenFileWrite ("Data.Txt",2);

if ( glbHandle!=0 )
{
setTimer (writeTimer,glbPeriod);
}
else
{
write ("File 'Data.Txt' was not opened for write access.");
}
}
on timer writeTimer
{
long randomValue;
char buffer [64];

if ( glbHandle!=0 )
{
randomValue = random (32767);
snprintf (buffer,elcount(buffer)," %d \n",randomValue);
filePutString (buffer, elcount(buffer),glbHandle);
setTimer (writeTimer,glbPeriod);
}
else
{
write ("Error, invalid file handle.");
}
}

on StopMeasurement
{
fileClose (glbHandle);
}