Programming Perl, 4th Edition

seek

seek FILEHANDLE, OFFSET, WHENCE

This function positions the file pointer for FILEHANDLE, just like the fseek(3) call of standard I/O. The first position in a file is at offset 0, not offset 1. Also, offsets refer to byte positions, not character positions or line numbers. In general, since line lengths vary, it’s not possible to access a particular line number without examining the whole file up to that point, unless all your lines are known to be of a particular length, or you’ve built an index that translates line numbers into byte offsets. (The same restrictions apply to character positions in files with variable-length character encodings like UTF-8 and UTF-16: the operating system doesn’t know what characters are, only bytes.)

FILEHANDLE can be an expression whose value gives either the name of the actual filehandle, a typeglob, or a reference to anything resembling a filehandle object. The function returns true on success, and false otherwise. For handiness, the function can calculate offsets from various file positions for you. The value of WHENCE specifies which file position your OFFSET uses for its starting point: 0, the beginning of the file; 1, the current position in the file; or 2, the end of the file. The OFFSET can be negative for a WHENCE of 1 or 2. If you’d like ...