"Public Domain cpio.c"

[Dan Kary]

A while back there was a discussion about reading cpio format tapes on 4.2BSD
systems. We lost news for a while and I never found out how or if the problem
was resolved. Faced with a need to read a cpio tape I finally decided to
write something that would read cpio format. It turned out to be a much
smaller problem than I thought it would be. No guarantees about portability
are made, but I was able to read my AT&T System V distribution tape on our
VAX 11/780 running 4.2BSD with this program. I hope this is useful to someone.

Dan Kary

(one file only)
--------------------- cut here -----------------------------------
/* A public domain program by Daniel D. Kary
* 300 Minard Hall
* North Dakota State University
* Fargo, ND 58105
* ihnp4!dicomed!ndsuvax!nckary
*
* This program will read cpio format files (tapes)
* use dd(1) to read the tape into a file then 'cpio file'
* to read the files out of the tape file. This program will
* create directories and files using the correct mode and
* ignoring time, user and group info. It is useful for reading
* distribution tapes (AT&T) on systems lacking cpio (Berkeley).
* The process's effective user ID must be super-user.
*/

#include <sys/types.h>
#include <sys/file.h>
#include <stdio.h>

struct header{
ushort magic_number,
device,
inode,
mode,
uid,
gid,
h_nlink,
dev_type,
modify_time[2],
name_length,
file_size[2];
}
hdr;

char buf[10240], fname[512];
int fd;

main(argc, argv)
int argc;
char *argv[];
{
if(argc != 2){
fprintf(stderr,"Usage: cpio filename\n");
exit();
}
fd = open(argv[1], O_RDONLY);
while(fd > 0){
read_hdr();
if(strcmp("TRAILER!!!", fname) == 0) exit();
}
}

read_hdr()
{
char c;
int f, i, size;

read(fd, &hdr.magic_number,2);
read(fd, &hdr.device,2);
read(fd, &hdr.inode,2);
read(fd, &hdr.mode,2);
read(fd, &hdr.uid,2);
read(fd, &hdr.gid,2);
read(fd, &hdr.h_nlink,2);
read(fd, &hdr.dev_type ,2);
read(fd, hdr.modify_time,4);
read(fd, &hdr.name_length,2);
read(fd, &hdr.file_size[1],2);
read(fd, &hdr.file_size[0],2);
i = hdr.name_length;
if(((i/2)*2) != i) i++;
read(fd, fname, i);
size = hdr.file_size[1] * 65536 + hdr.file_size[0];
if(((size/2)*2) != size) size++;
if(size == 0)
mkdir(fname, hdr.mode);
else{
f = open(fname, O_CREAT | O_WRONLY, hdr.mode);
while(size >= 10240){
read(fd, buf, 10240);
write(f, buf, 10240);
size -= 10240;
}
if(size > 0){
read(fd, buf, size);
write(f, buf, size);
close(f);
}
}
}