bash script retrieve dbus output

Question

Today, I have to retrieve the result of dbus command.

dbus-send --session --print-reply --dest="com.ac.comp" /com/ac/comp/Time com.ac.comp.Time.GetTime

When I execute the above command, I obtain the following output :

method return sender=:1.0 -> dest=:1.34 reply_serial=2
   byte 0
   byte 0
   byte 0
   byte 0
   byte 0
   byte 0
   uint16 0

Values are given according to the following order :

second
minute
hour
weekday
dateday
month
year

I have implemented my bash as follow :

dbus-send --session --print-reply --dest="com.ac.comp" /com/ac/comp/Time com.ac.comp.Time.GetTime | grep -E byte | cut -c 9-11 > "$file" 
dbus-send --session --print-reply --dest="com.ac.comp" /com/ac/comp/Time com.ac.comp.Time.GetTime | grep -E uint16 | cut -c 11-13 >> "$file" 

second=$(sed -n '1p' < $file)
minute=$(sed -n '2p' < $file)
hour=$(sed -n '3p' < $file)
weekday=$(sed -n '4p' < $file)
dateday=$(sed -n '5p' < $file)
month=$(sed -n '6p' < $file)
year=$(sed -n '7p' < $file) 
echo -e "Time ==> Day : $weekday - Date : $dateday/$month/$year - Time : $hour:$minute:$second"

The job is done correctly. However, I am sure that my script could be maximized and dbus has not to be called twice and there is a way to do all stuff in less lines.

As new bash programmer, I need advices on this issue and to learn new methods.

you need not use extra redirection, sed is capable of reading input from file. That is sed -n '1p' $file would work fine — nu11p01n73R
– nu11p01n73R, Commented Nov 18, 2014 at 13:44
Thank ! I just tried your instruction, same result and seven lines removed --' — ogs
– ogs, Commented Nov 18, 2014 at 13:51
There's no need to pre-cut the file. sed can do that work as well (and in a less-error prone fashion). sed -e '1{s/^ \+(byte|uint16) //;p}' or something roughly like that. Though whether that will be more-or-less efficient depends on whether doing that work in N sed instances is better than doing it in one cut instance N times. — Etan Reisner
– Etan Reisner, Commented Nov 18, 2014 at 13:57
You mean that the sed command that you gave could generate the same output ? I tried with the same line and with modification but I obtain only the first line. Thank — ogs
– ogs, Commented Nov 18, 2014 at 14:28
I'm so sorry Etan but after one hour I am not able to apply your example and thus call dbus-send only one time and store only the byte and uint16 value. Could you give more details ? — ogs
– ogs, Commented Nov 18, 2014 at 15:29

ajaaskel · Accepted Answer · 2014-11-18 18:11:27Z

2

array=($(dbus-send --session --print-reply --dest="com.ac.comp" /com/ac/comp/Time com.ac.comp.Time.GetTime))

Maybe somewhere here what you are after:

echo "Seconds = ${array[7]}"
echo "Minutes = ${array[9]}"
.
.

answered Nov 18, 2014 at 18:11

ajaaskel

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2 Comments

ogs Over a year ago

Thank you ajaaskel ! It is a very good alternative, I am not obligated to create a file. However, I have to ask a last question. Why did you specify ${array[7]} to retrieve the first byte value ? Within the line "method return sender=:1.0 -> dest=:1.34 reply_serial=2" there is just five term ?

ajaaskel Over a year ago

I just counted from your output that you'll have first those extra strings you don't need and the first data might go to index 7 which is cell number 8 in that array since there is word "byte" before the actual value. i.e. 0:method 1:return 2:sender=:1.0 3:-> 4:..

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