Hi, I am trying to achieve faster file writes using mmap. so I am trying the follwowing: /* open file */ while (loop) { /* get the current file size of output file */ filesize = lseek(outfd, 0, SEEK_END); /* Increase file size */ ftruncate(outfd, (off_t)filesize + (off_t)buf.size); /* mmap destination file */ if((dest = mmap(0, buf.size, PROT_WRITE, MAP_SHARED, outfd, filesize)) == (void *) -1) { printf( "Error mapping ouput file: %s: %d, %d\n", argv[1], i, filesize); perror("MMAP Failed\n"); goto error; } memcpy(dest, src, size); munmap(dest); } I am able to only mmap it once next time it fails to mmap, any pointers why it fails ? Regards, --Sagar