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Not able to put ls -lR command in background

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Operating Systems Linux Not able to put ls -lR command in background
# 1  
Old 02-11-2014
Not able to put ls -lR command in background
Hi All,

i am trying to put ls -lRt command to run in the background but it fails.
i continue to get output on screen and didnt get the command prompt right after i put the command in background.
command i am using is
Code:
 
ls -lRt &

i am using bash.

Can someone let me know how to resolve this.
# 2  
Old 02-11-2014
And where do you want to fetch the data?

You might like/use:
Code:
ls -lRt > ~/fetched-ls.txt &

That will redirect all output (of stdout) to the file $HOME/fetched-ls.txt, and doing so in background.
Just be sure the process is done before using the outputfile.

Hope this helps
# 3  
Old 02-11-2014
thanks 'sea'...is it possible to put the output of command (stdout) in the background without redirecting.
in a nutshell after i fire command ls -lRt & , command prompt should return so that i can execute another command. and once the execution of the ls -lRt is over in the background it should display the stdout on the screen.
# 4  
Old 02-11-2014
AFAIK:
You can either redirect the output somewhere else or not.
But you cannot 'buffer' it, unless you use a file, variable or reduce the output by using pipes.

In case of a variable you could try: DATA=$(ls -1Rt) & then continue your work, and when its done, type: echo "$DATA"

Otherwise, please explain what you are trying to achieve.

hth
# 5  
Old 02-12-2014
thanks sea...i am new to this unix world..so trying to learn the actual difference between the foreground and background process.

Now i have clear idea about it..thanks for the information and knowledgeSmilie
# 6  
Old 02-12-2014
That will not work, since the variable will get set in a subshell and therefore will not retain its value once it returns..

You could use a named pipe:
Code:
mkfifo somepipe
ls -lR > somepipe &
echo hello
cat < somepipe
rm somepipe

Or in bash / ksh93
Code:
exec 3< <(ls -lR)
echo hello
cat <&3

In ksh93 you can use a co-process
Code:
ls -lR |&
echo hello
while IFS= read -rp line
do
  printf "%s\n" "$line"
done

In bash 4 also:
Code:
coproc ls -lR
echo hello
cat <&${COPROC[0]}

Last edited by Scrutinizer; 02-12-2014 at 03:58 AM..
# 7  
Old 02-12-2014
thanks Scrutinizer Smilie
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