On Sunday 23 January 2005 11:49 pm, you wrote: > Hi, > > I would like to know how to implement "tail -n" in C. > > The "-n" option will be used to print the last n lines of a file - > rather than the default option of printing the last 10 lines of a file. > > I wish to do this in a single pass. I can use lseek() to go to the end > of the file. How to traverse backwards from there ? Is there any > function that does this ?
Not that I know of. There is no GOOD way to do this in a single pass since the lines can be of varying length. If by single pass you meant you want performace, then dont read a char at a time, rather just seek to the end of the file, read in about 4K( a reasonable buffer) or so and see if you can find (n+1) newlines. If you dont, read in 4 more k and keep going backwards till you find them. P.S. Please dont hi-jack subjects. Type in a new message instead of replying to something and deleting the original message; it screws with threading. > thanks, > venkatesh > - > To unsubscribe from this list: send the line "unsubscribe > linux-c-programming" in the body of a message to [EMAIL PROTECTED] > More majordomo info at http://vger.kernel.org/majordomo-info.html -- ---------------------------------------- --EB > All is fine except that I can reliably "oops" it simply by trying to read > from /proc/apm (e.g. cat /proc/apm). > oops output and ksymoops-2.3.4 output is attached. > Is there anything else I can contribute? The latitude and longtitude of the bios writers current position, and a ballistic missile. --Alan Cox LKML-December 08,2000 ---------------------------------------- - To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
