file-character-position

Arguments: simple-stream

This generic function tries to determine the character position of its simple-stream argument, similar to stream-line-column which tries to determine the character number from the beginning of a line. The value returned is a non-negative integer or nil.

The first character in a file has character position 0 (following Lisp practice of numbering things starting at 0). Some editors (Emacs being an example) consider the character position of the first character to be 1. So Emacs command "M-x goto-char 2 1 RET" goes to character position 20. Emacs users and users of other editors which consider the first character to have position 1 should take this difference into account.

nil means that the value cannot be determined. This can happen, for example, if bytes rather than characters have been read from simple-stream or the file-position has been set. Unlike stream-line-column, which can re-synchronize itself after reading a newline, file-character-position cannot; it can only re-synchronize itself when the file-position starts at zero and only characters are read.

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Created 2012.5.30.