Like GNU dd(1) similar operands, iflag and oflag allow specifying the
O_* flags given to open(2) for the input and the output file. The values
are comma-sepratated, lower-case, O_ prefix-stripped constants documented
in open(2).
Since iflag and oflag override default values, specifying oflag means
O_CREATE is not set by default and must be specified explicitely.
Some values do not make sense (e.g.: iflag=directory) but are still used
and will raise a warning. For oflag, values rdonly, rdwr and wronly are
filtered out with a warning (dd(1) attempts open(2) with O_RDWR and
then O_WRONLY on failure).
Specifying oflag=trunc along with (seek, oseek or conv=notrunc) is
contradictory and will raise an error.
iflag and oflag are disabled if building with -DMALLPROG
output of the information summary returned by dd(1). This can be used
to specify messages in a more usable (or parseable) format like
human-readable values.
My intent is to re-use this for building image files and quick I/O
benchmarking.
Reviewed by tsutsui@ on tech-userlevel. See also
http://mail-index.netbsd.org/tech-userlevel/2010/12/03/msg004179.html
Some examples:
$ dd if=/dev/zero of=/dev/null bs=1m count=1 msgfmt=human
1+0 records in
1+0 records out
1048576 bytes (1,0 MB) transferred in 0.001 secs (1048576000 bytes/sec - 1,0 GB/sec)
$ dd if=/dev/zero of=/dev/null count=1 msgfmt='
> <speed>%E</speed>
> <time>%s</time>
> <bytes>%b</bytes>
> '
<speed>500 KB/sec</speed>
<time>0.001</time>
<bytes>512</bytes>
"if" and "of" with the exception that the communicate with a rump
kernel instead of the host kernel.
For example, to write stdout to /tmp/file.txt in a rump kernel namespace:
dd rof=/tmp/file.txt
copy /file1 to /file2 inside a rump kernel:
dd rif=/file1 rof=/file2
copy a snippet from /dev/rmd0d on the rump kernel to the host fs:
dd rif=/dev/rmd0d of=save seek=1000 count=3
Eat that, usermode OS.
(I'll document the operands one I have some manpage to refer to
for rump client use).
- Add strsuftoull(), which parses a number into a u_longlong_t, with
multiplication support, and support for 'g' (GB) and 't' (TB) suffices.
If an error occurs, print to stderr and exit.
Based on get_blk() from args.c and strsufto*() (in other programs)
- Add strsuftoullx(), which acts as per strsuftoull() but returns the
error in the supplied buffer instead (if the returned buffer != "", an
error occurred)
- Replace get_bsz() use with strsuftoull()
- Remove (now) unnecessary argument validation
- Remove unused {f,p,s,t}_stats fields in struct IO
manu