[Lzip-bug] non-S_ISREG files

[John Reiser]

Hi,

Currently open_instream()/main.cc rejects any non-S_ISREG file.
This causes trouble with
   S_ISFIFO  named pipe
   S_ISSOCK  socket
   S_ISLNK   symbolic link
   /dev/stdin   Linux-specific symlink to /proc/self/fd/0
   /proc/<pid>/fd/n  Linux-specific symlink
   S_ISBLK   block special device
   S_ISCHR   character special device

I would like to see an enhancement so that S_ISFIFO, S_ISSOCK, and
S_ISLNK are treated as if they were piped to stdin, and either create
a new output file or use stdout.  Give a warning on stderr if not in
--quiet mode.  Treat the input as a read-only unnamed data stream.
Do not manipulate the file by replacing its contents with the compressed
version and appending ".lz", etc.

"But the user could just pipe the fifo/socket/symlink as stdin
in the first place."  This is true when running lzip directly, such as
from the top-level of an interactive shell.  However, when using lzip
from within a script or another utility program, then it is a useful
convenience, simplification, and reduction in complexity to avoid
special cases.   Also, there are useful situations where a "cabal
of processes" is involved: something other than a sequential linear
pipeline of processes.  The most common example is running /bin/cmp
with two generated input streams (pipes).  Something approximately like:
   ...  |  /bin/cmp - /proc/self/fd/6
where the establishment of fd6 can be difficult to express in shell.

Treating S_ISBLK and S_ISCHR as if they were pipes is analogous
but the usage is much less frequent.  (The case where S_ISBLK is a
whole filesystem comes to mind.)  I feel less strongly
about these two cases than I do about fifo/socket/symlink.


Regards,

-- 
John Reiser