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Top Forums Programming unexpected values received when writing and reading from file Post 302477166 by saman_glorious on Friday 3rd of December 2010 12:25:29 PM
Old 12-03-2010
I am so sorry i just noticed you asked me the compilable code.

I am writing the code for a single file, i can't directly store an integer in a file as it wouldn't be readable, i have to use sprintf convert it to a string and then write it. i think the problem is that the write() operation writes the whole string
see

Code:
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<errno.h>
#include<fcntl.h>
#include<ctime>
#include<cmath>
#include<iostream>
using namespace std;
#define FILE_MODE  (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)
#define _PARAM 5
#define _RAND_RANGE 100
#define DOWNLOADER_FIFO "/tmp/fifo.0"

int main(int argc, char **argv){
   int fd, value = 19;
   int n;
   char c[10];

   if( (fd = open("file.txt", O_WRONLY | O_CREAT, FILE_MODE) ) < 0 ){
        perror("file creation failed..\n");
          return false;
   }      sprintf(c, "%d", value);
          if((n = write(fd, c, sizeof c)) < 0){
                  perror("\n");
                     return false;} 
   close(fd);

return 0;
}

 

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stat.h(3HEAD)							      Headers							     stat.h(3HEAD)

NAME
stat.h, stat - data returned by stat system call SYNOPSIS
#include <sys/types.h> #include <sys/stat.h> DESCRIPTION
The system calls stat, lstat and fstat return data in a stat structure, which is defined in <stat.h>. The constants used in the st_mode field are also defined in this file: #define S_IFMT /* type of file */ #define S_IAMB /* access mode bits */ #define S_IFIFO /* fifo */ #define S_IFCHR /* character special */ #define S_IFDIR /* directory */ #define S_IFNAM /* XENIX special named file */ #define S_INSEM /* XENIX semaphore subtype of IFNAM */ #define S_INSHD /* XENIX shared data subtype of IFNAM */ #define S_IFBLK /* block special */ #define S_IFREG /* regular */ #define S_IFLNK /* symbolic link */ #define S_IFSOCK /* socket */ #define S_IFDOOR /* door */ #define S_ISUID /* set user id on execution */ #define S_ISGID /* set group id on execution */ #define S_ISVTX /* save swapped text even after use */ #define S_IREAD /* read permission, owner */ #define S_IWRITE /* write permission, owner */ #define S_IEXEC /* execute/search permission, owner */ #define S_ENFMT /* record locking enforcement flag */ #define S_IRWXU /* read, write, execute: owner */ #define S_IRUSR /* read permission: owner */ #define S_IWUSR /* write permission: owner */ #define S_IXUSR /* execute permission: owner */ #define S_IRWXG /* read, write, execute: group */ #define S_IRGRP /* read permission: group */ #define S_IWGRP /* write permission: group */ #define S_IXGRP /* execute permission: group */ #define S_IRWXO /* read, write, execute: other */ #define S_IROTH /* read permission: other */ #define S_IWOTH /* write permission: other */ #define S_IXOTH /* execute permission: other */ The following macros are for POSIX conformance (see standards(5)): #define S_ISBLK(mode) block special file #define S_ISCHR(mode) character special file #define S_ISDIR(mode) directory file #define S_ISFIFO(mode) pipe or fifo file #define S_ISREG(mode) regular file #define S_ISSOCK(mode) socket file ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
stat(2), types.h(3HEAD), attributes(5), standards(5) SunOS 5.10 30 Aug 2002 stat.h(3HEAD)
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