stdio data from write not making it into a file
- by user1551209
I'm having a problem with using stdio commands for manipulating data in a file. I short, when I write data into a file, write returns an int indicating that it was successful, but when I read it back out I only get the old data.
Here's a stripped down version of the code:
fd = open(filename,O_RDWR|O_APPEND);
struct dE *cDE = malloc(sizeof(struct dE));
//Read present data
printf("\nreading values at %d\n",off);
printf("SeekStatus <%d>\n",lseek(fd,off,SEEK_SET));
printf("ReadStatus <%d>\n",read(fd,cDE,deSize));
printf("current Key/Data <%d/%s>\n",cDE->key,cDE->data);
printf("\nwriting new values\n");
//Change the values locally
cDE->key = //something new
cDE->data = //something new
//Write them back
printf("SeekStatus <%d>\n",lseek(fd,off,SEEK_SET));
printf("WriteStatus <%d>\n",write(fd,cDE,deSize));
//Re-read to make sure that it got written back
printf("\nre-reading values at %d\n",off);
printf("SeekStatus <%d>\n",lseek(fd,off,SEEK_SET));
printf("ReadStatus <%d>\n",read(fd,cDE,deSize));
printf("current Key/Data <%d/%s>\n",cDE->key,cDE->data);
Furthermore, here's the dE struct in case you're wondering:
struct dE {
int key;
char data[DataSize];
};
This prints:
reading values at 1072
SeekStatus <1072>
ReadStatus <32>
current Key/Data <27/old>
writing new values
SeekStatus <1072>
WriteStatus <32>
re-reading values at 1072
SeekStatus <1072>
ReadStatus <32>
current Key/Data <27/old>
