lseek |
  
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lseek |
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The lseek() function repositions the offset of the open file associated with the file descriptor fd to the argument offset
according to the directive whence as follows:
SEEK_SET
The offset is set to offset bytes.
SEEK_CUR
The offset is set to its current location plus offset bytes.
SEEK_END
The offset is set to the size of the file plus offset bytes.
int lseek(int fd,int offset,int whence);
Example :
#define EMBEDTRON "www.embedtron.com"
#define BUFFER_SIZE 20
int main()
{
char buffer[BUFFER_SIZE];
int len = 0;
int fh = 1;
if((fh=open("file.txt","w" )) == -1)
{
printf("Create file failed");
return -1;
}
if((len = write(fh,EMBEDTRON,strlen(EMBEDTRON))) != strlen(EMBEDTRON))
{
printf("Write data failed");
return -2;
}
close(fh);
if((fh=open("file.txt","r" )) == -1)
{
printf("Create file failed");
return -1;
}
lseek(fh, 0, SEEK_END);
len = tell(fh);
lseek(fh, 0, SEEK_SET);
if((len = read(fh,buffer,BUFFER_SIZE)) != strlen(EMBEDTRON))
{
printf("Read data failed");
return -3;
}
buffer[len] = '\0';
printf("String = %s Size = %d \n",buffer,len);
close(fh);
return 0;
}