./binary < file
binary's stdin is the file open in read-only mode. Note that
bash doesn't read the file at all, it just opens it for reading on the file descriptor 0 (stdin) of the process it executes
./binary << EOF
Depending on the shell,
binary's stdin will be either a deleted temporary file (AT&T ksh, zsh, bash...) that contains
test\n as put there by the shell or the reading end of a pipe (
yash; and the shell writes
test\n in parallel at the other end of the pipe). In your case, if you're using
bash, it would be a temp file.
cat file | ./binary
Depending on the shell,
binary's stdin will be either the reading end of a pipe, or one end of a socket pair where the writing direction has been shut down (ksh93) and
cat is writing the content of
file at the other end.
When stdin is a regular file (temporary or not), it is seekable.
binary may go to the beginning or end, rewind, etc. It can also mmap it, do some
ioctl()s like FIEMAP/FIBMAP (if using
<> instead of
<, it could truncate/punch holes in it, etc).
pipes and socket pairs on the other hand are an inter-process communication means, there's not much
binary can do beside
reading the data (though there are also some operations like some pipe-specific
ioctl()s that it could do on them and not on regular files).
Most of the times, it's the missing ability to
seek that causes applications to fail/complain when working with pipes, but it could be any of the other system calls that are valid on regular files but not on different types of files (like
fallocate()). On Linux, there's also a big difference in behaviour when you open
/dev/stdin while the fd 0 is on a pipe or on a regular file.
There are many commands out there that can only deal with seekable files, but when that's the case, that's generally not for the files open on their stdin.
$ unzip -l file.zip
Length Date Time Name
--------- ---------- ----- ----
11 2016-12-21 14:43 file
11 1 file
$ unzip -l <(cat file.zip)
# more or less the same as cat file.zip | unzip -l /dev/stdin
End-of-central-directory signature not found. Either this file is not
a zipfile, or it constitutes one disk of a multi-part archive. In the
latter case the central directory and zipfile comment will be found on
the last disk(s) of this archive.
unzip: cannot find zipfile directory in one of /proc/self/fd/11 or
/proc/self/fd/11.zip, and cannot find /proc/self/fd/11.ZIP, period.
unzip needs to read the index stored at the end of the file, and then seek within the file to read the archive members. But here, the file (regular in the first case, pipe in the second) is given as a path argument to
unzip opens it itself (typically on fd other than 0) instead of inheriting a fd already opened by the caller. It doesn't read zip files from its stdin. stdin is mostly used for user interaction.
If you run that
binary of yours without redirection at the prompt of an interactive shell running in a terminal emulator, then
binary's stdin will be inherited from its caller the shell, which itself will have inherited it from its caller the terminal emulator and will be a pty device open in read+write mode (something like
Those devices are not seekable either. So, if
binary works OK when taking input from the terminal, possibly the issue is not about seeking.
If that 14 is meant to be an errno (an error code set by failing system calls), then on most systems, that would be
EFAULT (Bad address). The
read() system call would fail with that error if asked to read into a memory address that is not writable. That would be independent of whether the fd to read the data from points to a pipe or regular file and would generally indicate a bug1.
binary possibly determines the type of file open on its stdin (with
fstat()) and runs into a bug when it's neither a regular file nor a tty device.
Hard to tell without knowing more about the application. Running it under
tusc equivalent on your system) could help us see what is the system call if any that is failing here.
1 The scenario envisaged by Matthew Ife in a comment to your question sounds a lot plausible here. Quoting him:
I suspect it is seeking to the end of file to get a buffer size for reading the data, badly handling the fact that seek doesn't work and attempting to allocate a negative size (not handling a bad malloc). Passing the buffer to read which faults given the buffer is not valid.