Package: busybox Version: 1:1.22.0-6 Severity: wishlist Dear Maintainer,
In udebs, it is common to redirect the standard output of a command to
a fifo, and use that to display progress bars in the installer.
trap 'kill $pid' EXIT
/path/to/command >"$fifo" &
while read -u 7 n; do
db_progress SET $n
done 7< "$fifo"
rm -f "$fifo"
trap - EXIT
However, if the command buffers its standard output, which for instance
is what cryptsetup(8) does, and/or if the standard output needs to be
piped through sed(1) (which also buffers its standard streams), it's
hard to make sense of the progress bar, which suddenly jumps from 0% to
100% while nothing happens in the meantime.
cryptsetup -q --key-file="$keyfile" luksFormat "$device" | \
sed -nr 's/^Generating key \(([0-9]+)% done\)\.$/\1/p' > "$fifo" &
It'd be convenient to provide a way to disable buffering in STDOUT, in
the fashion of stdbuf(1) from GNU coreutils [1]. If the full blown
stdbuf(1) is overkill, it might still be desirable to add a strip down
version disabling buffering only, as found in [2]:
:/lib/stdbuf.c
#include <stdio.h>
__attribute__ ((constructor)) void
QLqxcKVd20zweBii () {
setvbuf (stdout, NULL, _IOLBF, 0);
}
$ gcc -Wall -x c -s /lib/stdbuf.c -fPIC -shared -o /lib/stdbuf.so
:/bin/stdbuf
#!/bin/sh
LD_PRELOAD=/lib/stdbuf.so "$@"
Then buffering of STDOUT could be disabled as follows:
stdbuf cryptsetup -q --key-file="$keyfile" luksFormat "$device" | \
stdbuf sed -nr 's/^Generating key \(([0-9]+)% done\)\.$/\1/p' > "$fifo" &
Thanks!
Cheers,
--
Guilhem.
[1] http://git.savannah.gnu.org/gitweb/?p=coreutils.git;a=blob;f=src/stdbuf.c
[2] https://lists.gnu.org/archive/html/bug-coreutils/2008-11/msg00138.html
-- System Information:
Debian Release: jessie/sid
APT prefers unstable
APT policy: (990, 'unstable'), (800, 'testing'), (700, 'stable'), (1,
'experimental')
Architecture: i386 (i686)
Kernel: Linux 3.14-1-686-pae (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Versions of packages busybox depends on:
ii libc6 2.19-1
busybox recommends no packages.
busybox suggests no packages.
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