Chapter 13: Problem 38

A negative offset causes the file’s read or write position to be moved __________ in the file from the position specified by the mode.

Short Answer

Expert verified

Answer: A negative offset causes the file position to move backwards in the file, relative to the starting point specified by the mode. This influences the point from which the file is read or written, leading to reading or writing data from a position that is offset negatively from the base position.

Step by step solution

Understanding file positions

File positions are specific points within a file that indicate the current position for reading or writing data. When opening a file for reading or writing, the file position is usually set to the beginning (or any specific point) of the file.

Understanding negative offset

An offset is a value that specifies how far the file position should be moved relative to its starting position. If the offset is positive, the file position will be moved forward (towards the end of the file), while if the offset is negative, the file position will be moved backward (towards the beginning of the file).

Relating negative offset to file position movement

Now, let's see how a negative offset causes the file position to move. Since a negative offset has a negative value, the file position will be moved in the opposite direction (opposite to the mode) in the file from the position specified by the mode. For example, if the mode is set to seek a position from the end of the file, applying a negative offset will cause the file position to be moved further away from the end of the file (i.e., towards the beginning of the file).

Example

Consider a file with the following content: ``` This is a sample text file. It contains multiple lines of text. ``` Suppose we open this file for reading and set the mode to seek a position from the end of the file (`os.SEEK_END`). If we apply a negative offset of -5, the file position will move 5 bytes back from the end of the file, placing the position before the word "text" (the file position is now at the "t" of "text"). Now, when we read the file, it would start reading data from the word "text" instead of reading from the end of the file.

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A negative offset causes the file’s read or write position to be moved __________ in the file from the position specified by the mode.

Short Answer

Step by step solution

Understanding file positions

Understanding negative offset

Relating negative offset to file position movement

Example

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