SetStreamPosition

SetStreamPosition[stream, n] sets the current point in an open stream.

Examples

Set stream position to the beginning:

stream = OpenRead["file.txt"];
SetStreamPosition[stream, 0]

Move to a specific byte position:

SetStreamPosition[stream, 100]

Read from a specific position:

SetStreamPosition[stream, 50];
ReadLine[stream]

Please visit the official Wolfram Language Reference for more details.