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Get status of dd running in background job

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# 1  
Old 10-08-2013
Get status of dd running in background job

Hello everyone

While working on TUI for scripts, there there came the idea to' add a command' for dd too.
That was, after 'wrapping' tar and wget either, to display their growing size and return the exit code with a textual-visual-feedback to the user.

Now displaying the filesize of a tarball or a file that is downoaded during a loop is quite easy.

What i'd like to get is the value of how many times BS (as in bytesize) has been written.

So it would look similar to (the console output):
Linux : [ Text User Interface ] : tui-download & tui-tar - YouTube
At around 0:40 of the video.

The full script is:
Note that tui-printf & tui-status can be replaced by 'printf' or 'echo'
tui-indi prints on each call the following of its previous -/|\

source tui loads in the configuration files/default variables not defined in this script.
#    Author:     Simon A. Erat (sea)
#    Contact:
#    Variable defaults
    ME="$(basename $0)"
    help_text="\r$ME ($script_version)
        \rUsage: $ME SOURCE TARGET
        \rWrites SOURCE to TARGET
        \rRequires root rights.
    source tui
#    Variable handling
    if [[ "$1" = "-h" ]] || [[ -z $2 ]];then
    echo -e "$help_text" && exit $RET_HELP;fi
#    Display
    CMD="dd if=$SOURCE of=$TARGET bs=$DD_BS status=none > /dev/zero"
    echo "$CMD" > $FILE_CMD ; chmod +x $FILE_CMD ; $FILE_CMD &
    sleep 0.3
    while [[ ! "" = "$(ps|grep -v tui|grep dd)" ]]
    do    sleep 0.7
        tui-printf "Writing $(basename $SOURCE) to $TARGET"  " [  $(tui-indi)   ]"
    tui-status $? "Written $(basename $SOURCE) to $TARGET"

Which works like it should.

According to the manpage, one's supposed to get job's info by:
Originally Posted by man dd
Sending a USR1 signal to a running 'dd' process makes it print I/O statistics to standard
error and then resume copying.

$ dd if=/dev/zero of=/dev/null& pid=$!
$ kill -USR1 $pid; sleep 1; kill $pid
So i've changed accordingly:
(removed because outdated)

Problem now is:
# | Writing sea-AwesomeWM-F19.iso to /dev/sdb )                                                                                                                                            [  /   ] | #63+0 records in
63+0 records out
264241152 bytes (264 MB) copied, 4.22988 s, 62.5 MB/s
# | Writing sea-AwesomeWM-F19.iso to /dev/sdb )                                                                                                                                            [  -   ] | #65+0 records in
65+0 records out
272629760 bytes (273 MB) copied, 5.19806 s, 52.4 MB/s
# | Writing sea-AwesomeWM-F19.iso to /dev/sdb )                                                                                                                                            [  \   ] | #66+0 records in
66+0 records out
276824064 bytes (277 MB) copied, 6.16454 s, 44.9 MB/s
# | Writing sea-AwesomeWM-F19.iso to /dev/sdb )                                                                                                                                            [  |   ] | #
^C130 ~ $

I hoped redirecting the stderr to a variable would keep DD quite...
How could i achieve this?

CMD="dd if=$SOURCE of=$TARGET bs=$DD_BS"
while [[ ! "" = "$(ps|grep -v tui|grep dd)" ]]
    do    sleep 0.7
        pid=$(ps|grep -v tui|grep dd|awk '{print $1}')
        kill -USR1 $pid 2&> $TUI_TEMP_FILE
        tmp=$(grep "," $TUI_TEMP_FILE|awk '{print $3" "$4}')
        tui-printf "Writing $(basename $SOURCE) to $TARGET $tmp)"  " [  $(tui-indi)   ]"

---------- Post updated at 16:39 ---------- Previous update was at 15:14 ----------

According to the manpages, this is supposed to work:
Originally Posted by man bash
Note that the order of redirections is significant. For example, the command

ls > dirlist 2>&1

directs both standard output and standard error to the file dirlist, while the command

ls 2>&1 > dirlist

directs only the standard output to file dirlist, because the standard error was dupli‐
cated from the standard output before the standard output was redirected to dirlist.
However, i have tried:
  1. kill -USR1 $pid 1&>2 > $TUI_TEMP_FILE
  2. kill -USR1 $pid 2&>1 > $TUI_TEMP_FILE
  3. kill -USR1 $pid > $TUI_TEMP_FILE > 2&>1
  4. CMD="dd if=$SOURCE of=$TARGET bs=$DD_BS > $TUI_TEMP_FILE > 2&>1" # status=none
In all caes $TUI_TEMP_FILE remained empty, while - if there were output - it was only shown to user but not written to tempfile.

It seems dd is either 'spamy' or dead-silent...
Any hints welcome. (or what am i understanding wrong?)

Last edited by sea; 10-08-2013 at 11:33 AM..
# 2  
Old 10-08-2013
I would suspect more kill than dd... ( Last time I tried a kill fancy option I finished going in the white room to restart to box I lost control on...)
# 3  
Old 10-08-2013
You cannot redirect a process after you start it. If you want dd's stderr to write into a file, you have to redirect it there in the first place.
# 4  
Old 10-08-2013
Originally Posted by Corona688
You cannot redirect a process after you start it. If you want dd's stderr to write into a file, you have to redirect it there in the first place.
Guess i tried that with:
    CMD="dd if=$SOURCE of=$TARGET bs=$DD_BS "
    $CMD &  > $TUI_TEMP_FILE > 2&>1

But doesnt work -- keep getting all info on each loop to stout, but not to the file

Last edited by sea; 10-08-2013 at 01:34 PM..
# 5  
Old 10-08-2013
You are blanking the output file every time you kill, too. Remove that pile of redirections from kill.
# 6  
Old 10-08-2013
Pure silence (fail)
dd if=/dev/random of=/dev/zero & 2&>1 > /tmp/tmp
pid=$(ps|grep dd|awk '{print $1}')
while [[ ! "" = "$(ps|grep dd)" ]]
do     #kill -USR1 $pid
    grep "," /tmp/tmp | grep -v "+"|awk '{$2" "$3}'

Full spam (fail):
dd if=/dev/random of=/dev/zero & 2&>1 > /tmp/tmp
pid=$(ps|grep dd|awk '{print $1}')
while [[ ! "" = "$(ps|grep dd)" ]]
do     kill -USR1 $pid
    grep "," /tmp/tmp | grep -v "+"|awk '{$2" "$3}'

0+5 records in
0+0 records out
0 bytes (0 B) copied0 bytes (0 B) copied, 20.7462 s, 0.0 kB/s
, 2.36932 s, 0.0 kB/s
0+5 records in
0+0 records out
0+0 records in
0+0 records out
0 bytes (0 B) copied, 2.38147 s, 0.0 kB/s
0 bytes (0 B) copied, 20.7584 s, 0.0 kB/s
0+20 records in
0+0 records out
0 bytes (0 B) copied, 49.2783 s, 0.0 kB/s

All i want to achieve is "NO 'plain-dd' output" as above, but only this part: "0 bytes (0 B) copied" so i can print it on 1 line, 'staying' that very 1 line to the user, without the console spammed.

As in $tmp contains only "20mb" -- "25mb" -- "50mb" ...
Once i could 'mute' the DD output to the user, but still retrieve the values, even with the 0+0 records, i could 'cut' it down to the value needed, but this redirection stuff drives me crazy!! SmilieSmilie

Last edited by sea; 10-08-2013 at 02:02 PM..
# 7  
Old 10-08-2013
One problem: dd if=/dev/random of=/dev/zero quits instantly on my system. /dev/zero isn't something you can write to.

Also: 2&>1 is garbled, you want 2>&1.
This User Gave Thanks to Corona688 For This Post:

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