Finding the First Line of Data in a Plain Text Data File

// This snippet illustrates how to load data from a text file when there is a variable
// length header before the data. The technique is to read the file line-by-line
// using FReadLine, looking for the first data line. In this case the header ends
// with a line that starts like this:
//	"[DATA...]
// We look for that pattern to identify where the data starts.

Function FindFirstDataLine(pathName, filePath)
	String pathName		// Name of symbolic path or ""
	String filePath			// Name of file or partial path relative to symbolic path.

	Variable refNum

	Open/R/P=$pathName refNum as filePath
	
	String buffer, text
	Variable line = 0
	
	do
		FReadLine refNum, buffer
		if (strlen(buffer) == 0)
			Close refNum
			return -1						// The expected keyword was not found in the file
		endif
		text = buffer[0,4]
		if (CmpStr(text, "[DATA") == 0)		// Line does start with "[DATA" ?
			Close refNum
			return line + 1					// Success: The next line is the first data line.
		endif
		line += 1
	while(1)
	
	return -1		// We will never get here
End

Function LoadDataFile(pathName, filePath, extension)
	String pathName		// Name of symbolic path or "" to display dialog.
	String filePath			// Name of file or "" to display dialog. Can also be full or partial path relative to symbolic path.
	String extension			// e.g., ".dat" for .dat files. "????" for all files.
 
	Variable refNum
 
	// Possibly display Open File dialog.
	if ((strlen(pathName)==0) || (strlen(filePath)==0))
		Open /D /R /P=$pathName /T=(extension) refNum as filePath
		filePath = S_fileName			// S_fileName is set by Open/D
		if (strlen(filePath) == 0)		// User cancelled?
			return -1
		endif
		// filePath is now a full path to the file.
	endif
	
	Variable firstDataLine = FindFirstDataLine(pathName, filePath)
	
	if (firstDataLine < 0)
		Printf "No data found in file %s\r", filePath
		return -1
	endif
 
	LoadWave /J /D /O /E=1 /K=0 /L={0,firstDataLine,0,0,0} /P=$pathName filePath
 
	return 0
End