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To: "Ajay Bansal" <Ajay_Bansal@infosys.com>
Cc: <redhat-devel-list@redhat.com>, <gcc-help@gcc.gnu.org>
Subject: Re: Fgets is not working on linux/gcc3.2.1
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References: <2B721C6525F0D411B1E900B0D0226BDD027DCC6D@mohmsg01.ad.infosys.com>
From: LLeweLLyn Reese <llewelly@lifesupport.shutdown.com>
Date: Thu, 10 Apr 2003 14:45:00 -0000
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"Ajay Bansal" <Ajay_Bansal@infosys.com> writes:

> Hi All
> 
> Following program is not working on linux. Ideally it should read all
> the lines from "/tmp/log.txt" and print them on to the screen. Instead
> it breals after it encounters fgets for the first time.
> 
> Pleas tell me where I am going wrong!!!! This program is working as
> expected on a Solaris machine.
> 
> Regards
> -Ajay
> ------------------------------------------------------------------------
> -----------
> 
> Entries in log.txt
> ------------------
> Line1
> Line2
> Line3
> ------------------
> 
> Output of the program
> ---------------------
> [ajay@linux1 test]$ ./a.out 
> Fileno is :3
> Error no is : 0
> Error is : Success
> Line read is : 
>  after fgets break outside while loop
> ---------------------
> 
> #include <iostream>
> #include <fstream>
> #include <errno.h>
> #include <stdlib.h>
> using namespace std;
> int main()
> {
>     char * pszFileName = "/tmp/log.txt";
>     char * pszMode = "a+";
>     char lpsz[4096];
>     FILE *pFile = fopen(pszFileName, pszMode);

      fseek(pFile,0,SEEK_BEG);

will fix your problem. On solaris, where a file opened with a is
    opened at the begining, the above will have no effect. On linux,
    where the file is opened at the end, the above will seek to the
    begining. 


> 
>     while (!feof(pFile)) {
>         if (! fgets(lpsz, 4096, pFile))
>         {
>             cout<<"Error no is : "<<errno<<endl;
>             cout<<"Error is : "<<strerror(errno)<<endl;
>             cout<<"Line read is : "<<lpsz<<endl;
>             break;
>          }
> 	   cout<<"Line read is : "<<lpsz<<endl; 
>     	   cout <<" after fgets break inside while loop"<<endl;
>     }
> 
>     cout <<" after fgets break outside while loop"<<endl;
> 
>     return 1;
> }