How to read lines from end of a file?

[Darrell]

"Alexander Williams" <thantos at chancel.org> in message
news:slrn862rtb.732.thantos at chancel.org
was concerned about maxLen and half written lines.

Good idea the test for a  trailing CR, added that.

Maybe maxLen should be sys.maxint by default. Then paranoid or performance
concerned,  can tone it down from there.

import sys

def readLinesFromEnd(fn, maxLen=sys.maxint):
    """
    Read lines from the end of a file up to a max number of bytes.

    fn:: file name to read from
    maxLen:: max number of bytes to read
    """
    fp=open(fn)
        # seek to the end
    fp.seek(0,2)
        # seek back from the end
    fp.seek(-min(maxLen,fp.tell()),2)
        # Dump the first line
        # It might be chopped off
    lines=fp.readlines()[1:]

    if lines[-1][-1] != '\012':
        # The last line might be half written.
        lines=lines[:-1]

    return lines

def main():
    print readLinesFromEnd(sys.argv[1])


--
--Darrell