Is it possible to get cursor position in C?

Question

Hi,

I am reading a file with fgetc, so each time it reads a character, the cursor positio gets changed.

Is it possible to know, after each read, the "coordinates" of the cursor on the file in terms of column and line number?

Thanks

Answer 1

You can use ftell

It does not give you the position in terms of row and column but gives the current position in the stream from the start.

Answer 2

There is no "coordinates" in a file, only a position. A text file is simply a stream of bytes, and lines are separated by line breaks. So, when reading a text file you can calculate your "coordinates" if you scan the whole file. This means, if you really need some "row" and "column" value:

• Read the file line by line. Count the newline characters, and you get the "row" number. Be aware that there are different line break characters on different OS -- unix line endings are different to Windows.
• Read the line in question character by character and count the characters to the position in question. This will get you the "column" number. You obviously need to accept that the number of "columns" can vary between "rows", and it's perfectly possible to have "rows" with a "column count" of 0.

A different approach would be to

• Read the file line by line and build an array of the position (using ftell) of the line breaks.
• Now to figure the position of any character just get its position in the file, then find the nearest previous line break. From the line break count up to the character you get the "row", from the difference between the line break position and the current position you get the "column".

But most important is to accept that there is no rows or columns in files -- there's a position in a file, but the file itself is simply a stream of bytes. This also means that you would need to handle files encoded with wide character sets differently, as a character doesn't map to a byte anymore.