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Why output nothing to variable?

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# 1  
Old 10-07-2014
Why output nothing to variable?
Code:
root@SDP_Gaming_Socketed_GT3-1:/# rngd -r /dev/urandom -v
Available entropy sources:
    Intel/AMD hardware rng
    DRNG
root@SDP_Gaming_Socketed_GT3-1:/# x=`rngd -r /dev/urandom -v`
root@SDP_Gaming_Socketed_GT3-1:/# echo "$x" #get nothing

root@SDP_Gaming_Socketed_GT3-1:/# x=`eval rngd -r /dev/urandom -v`
root@SDP_Gaming_Socketed_GT3-1:/# echo "$x" #get nothing too

root@SDP_Gaming_Socketed_GT3-1:/#

# 2  
Old 10-07-2014
Shoving in an 'eval' when something doesn't work is a very dangerous habit.

Perhaps it's printing to stderr, try:

Code:
x=`rngd -r /dev/urandom -v 2>&1`

# 3  
Old 10-07-2014
Quote:
Originally Posted by Corona688
Shoving in an 'eval' when something doesn't work is a very dangerous habit.

Perhaps it's printing to stderr, try:

Code:
x=`rngd -r /dev/urandom -v 2>&1`


it doesn't work
Code:
root@SDP_Gaming_Socketed_GT3-1:~#  x=`rngd -r /dev/urandom -v 2>&1`
root@SDP_Gaming_Socketed_GT3-1:~# echo "$x"

root@SDP_Gaming_Socketed_GT3-1:~# rngd -r /dev/urandom -v 2>&1
Available entropy sources:
    Intel/AMD hardware rng

# 4  
Old 10-07-2014
Perhaps it only prints when the output is a terminal.
# 5  
Old 10-07-2014
Quote:
Originally Posted by Corona688
Perhaps it only prints when the output is a terminal.
it's code is
Code:
printf("\tIntel/AMD hardware rng\n");

this is strange
Last edited by Scrutinizer; 10-07-2014 at 10:38 PM.. Reason: code tags
# 6  
Old 10-07-2014
Surely there's some logic around it. Check for 'isatty'.
# 7  
Old 10-07-2014
Check the exit code:

Code:
x=`rngd -r /dev/urandom -v || echo "rngd failed: $?"`

rngd tends to write error messages to /var/log/messages - look for possible issues here
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