Thread: Last line or entry in a file

  1. #1
    Registered User
    Join Date
    Feb 2008

    Last line or entry in a file

    Does anyone know how I can read the last entry in a file? I have a file that I receive everyday but I want to only be able to report out the last entry or display the last entry as the file is quite large but new entries get written to it on a daily basis. 
    In such I will like it to display only entries for each current day in the file.
    I have downloaded the Bloodshed Dev-C++ and have tried using this program which I found online
    #include <stdio.h>
    #include <string.h>
    #define MYSIZE 10
    FILE *fp;
    char buf[MYSIZE + 1], buf2[MYSIZE + 1];
    char *ptr;
    fp = fopen("filename", "r");
    fseek(fp, MYSIZE, SEEK_END); 
    fread(buf, sizeof(char), MYSIZE, fp);
    ptr = strrchr(buf, '\n');
    if (ptr) {
       // We've found the data
       strcpy(buf2, ptr+1);
    Buy honestly I dont have a clue.  I have compiled it and run it and it stops at 
    fp = fopen("filename", "r");
    I have put in the following
    fp = fopen("ggg.txt", "r");
    but it still does not work? 

  2. #2
    Kernel hacker
    Join Date
    Jul 2007
    Farncombe, Surrey, England
    Try to put the code-tags around ONLY the code in your post - that way your explanation doesn't get really long.

    To find the last entry, you would have to read the file backwards. There are a couple of approaches, but the obvious one is to find the end of the file (fseek(f, 0, SEEK_END) will do that), use ftell() to find where the end is, and then use fseek(f, endpos - (numread+1), SEEK_SET), using fgetc() read the characters (into a string?), and check for a newline '\n' to be the input. [Obviously, there will be a newline at the VERY end too, so you need the previous newline to that].

    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

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