I have a while loop in which I am reading from an archive file and extracting the first file.
int fd = open(argv[2], O_RDWR | O_CREAT, 0666);
char name_buffer[16];
char size_buffer[10];
// go to the first header
lseek(fd, SARMAG, SEEK_CUR);
// store the number of bits read in a struct current_header
// until its size equal to the size of the entire
// header, or in other words, until the entire
// header is read
while ((num_read = read(fd, (char*) ¤t_header,
sizeof(struct ar_hdr))) == sizeof(struct ar_hdr))
{
// scans the current string in header and stores
// in nameStr array
sscanf(current_header.ar_name, "%s", name_buffer);
sscanf(current_header.ar_date, "%s", date_buffer);
sscanf(current_header.ar_uid, "%s", uid_buffer);
sscanf(current_header.ar_gid, "%s", gid_buffer);
int mode;
sscanf(current_header.ar_mode, "%o", &mode);
sscanf(current_header.ar_size, "%s", size_buffer);
sscanf(current_header.ar_fmag, "%s", fmag_buffer);
new_file_fd = open(name_buffer, O_WRONLY | O_CREAT | O_TRUNC);
int size = atoi(size_buffer);
char buf[size];
size_t count = size;
while ((n_read = read(fd, buf, size)) > 0)
{
n_write = 0;
do {
n = write(new_file_fd, &buf[n_write], n_read - n_write);
n_write += n;
} while (n_write < n_read);
}
close(new_file_fd);
}
lseek(fd, size + (size%2), SEEK_CUR);
For a given archive file with the structure:
!<arch>
File1 1382142494 501 20 100644 29 `
Testing 123
File2 1382142504 501 20 100644 23 `
Testing 246
The expected output should be a file "File1" that contains only the contents "Testing123".
Instead, I get File1 with the contents:
Testing 123
File2 1382142504 501 20 100644 23 `
Testing 246
For some reason, even though I've specified the amount of bits to read and write (parameter 3 is "size" which returns 29 -- the size of File1) it keeps reading and writing past 29 bytes.
Any ideas why this might be happening?