POSIX says that -c specifies a number of bytes, not characters. This
flag is commonly used by scripts that operate on binary files to things
like extract a header. Treating the offsets as character offsets will
break things in mysterious ways.
Instead, add a -m option (chosen to match `wc -m`, which also operates
on characters) to handle character offsets.
If we are just copying data from one file to another, we don't need to
fill a complete buffer, just read a chunk at a time, and write it to the
output.
POSIX says
Copying shall begin at the point in the file indicated by the -c
number or -n number options.
The origin for counting shall be 1; that is, -c +1 represents the
first byte of the file, -c -1 the last.
The origin for counting shall be 1; that is, -n +1 represents the
first line of the file, -n -1 the last.
getline(3) expects newline-terminated input. While glibc's
implementation seems to catch unterminated input and zero the
buffer, other versions (notably musl's) do not.
This is a workaround. Garbage will still be read, but
not printed.
Get rid of the !!()-constructs and use ret where available (or introduce it).
In some cases, there would be an "abort" on the first fshut-error, but we want
to close all files and report all warnings and then quit, not just the warning
for the first file.
In general, POSIX does not define /dev/std{in, out, err} because it
does not want to depend on the dev-filesystem.
For utilities, it thus introduced the '-'-keyword to denote standard
input (and output in some cases) and the programs have to deal with
it accordingly.
Sadly, the design of many tools doesn't allow strict shell-redirections
and many scripts don't even use this feature when possible.
Thus, we made the decision to implement it consistently across all
tools where it makes sense (namely those which read files).
Along the way, I spotted some behavioural bugs in libutil/crypt.c and
others where it was forgotten to fshut the files after use.
This has been a known issue for a long time. Example:
printf "word" > /dev/full
wouldn't report there's not enough space on the device.
This is due to the fact that every libc has internal buffers
for stdout which store fragments of written data until they reach
a certain size or on some callback to flush them all at once to the
kernel.
You can force the libc to flush them with fflush(). In case flushing
fails, you can check the return value of fflush() and report an error.
However, previously, sbase didn't have such checks and without fflush(),
the libc silently flushes the buffers on exit without checking the errors.
No offense, but there's no way for the libc to report errors in the exit-
condition.
GNU coreutils solve this by having onexit-callbacks to handle the flushing
and report issues, but they have obvious deficiencies.
After long discussions on IRC, we came to the conclusion that checking the
return value of every io-function would be a bit too much, and having a
general-purpose fclose-wrapper would be the best way to go.
It turned out that fclose() alone is not enough to detect errors. The right
way to do it is to fflush() + check ferror on the fp and then to a fclose().
This is what fshut does and that's how it's done before each return.
The return value is obviously affected, reporting an error in case a flush
or close failed, but also when reading failed for some reason, the error-
state is caught.
the !!( ... + ...) construction is used to call all functions inside the
brackets and not "terminating" on the first.
We want errors to be reported, but there's no reason to stop flushing buffers
when one other file buffer has issues.
Obviously, functionales come before the flush and ret-logic comes after to
prevent early exits as well without reporting warnings if there are any.
One more advantage of fshut() is that it is even able to report errors
on obscure NFS-setups which the other coreutils are unable to detect,
because they only check the return-value of fflush() and fclose(),
not ferror() as well.
It's not useful when 0 is returned anyway, so be sure that we have a
string with length > 0, this also solves some indexing-gotchas like
"len - 1" and so on.
Also, add checked getline()'s whenever it has been forgotten and
clean up the error-messages.
1) Specify default in manpage under flag.
2) Boolean and return value style fixes.
3) argv-argc-centric loop.
4) No need to check for argc == 1 before the fflag-subroutine.
5) Remove indentation.
6) Empty line before return.
Interface as proposed by cls, but internally rewritten after a few
considerations.
The code is much shorter and to the point, aligning itself with other
standard functions. It should also be much faster, which is not bad.
We cannot in general detect that truncation happened. At the moment
we use a heuristic to compare the file size before and after a write
happened. If the new file size is smaller than the old, we correctly
handle truncation and dump the entire file to stdout.
If it so happened that the new size is larger or equal to the old size
after the file had been truncated without any reads in between, we will
assume the data was appended to the file.
There is no known way around this other than using inotify or kevent
which is outside the scope of sbase.
