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What is the right way to redirect script output use ">" or ">>" ?

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# 1  
Old 04-03-2014
What is the right way to redirect script output use ">" or ">>" ?
Which one of the following are more accurate and why?
Code:
nohup myScript.sh 1>nohup_$(date +%Y%m%d%H%M%S).out 2>&1 &
nohup myScript.sh 1>>nohup_$(date +%Y%m%d%H%M%S).out 2>&1 &
nohup myScript.sh >nohup_$(date +%Y%m%d%H%M%S).out 2>&1 &
nohup myScript.sh  >>nohup_$(date +%Y%m%d%H%M%S).out 2>&1 &

I would go with 2nd line, but I am not sure why others are not better!!
# 2  
Old 04-03-2014
None of them is "wrong", they just do different things.

> creates a new file. If the file already exists, the old one is truncated.

>> appends an existing file (or creates a new file if there's nothing there).

The 1 and 2 are file descriptor numbers. If you don't give it a number, it assumes 1, for standard output.
# 3  
Old 04-03-2014
Since this is generating output file dynamically, is it ever possible that, the output file will get overwritten by new output from a subshell or something coming from script !? will it be wise to use >> if such possibility exists for this case?
Code:
 myScript.sh >nohup_$(date +%Y%m%d%H%M%S).out

# 4  
Old 04-03-2014
Quote:
Originally Posted by kchinnam
Since this is generating output file dynamically, is it ever possible that, the output file will get overwritten by new output from a subshell or something coming from script !? will it be wise to use >> if such possibility exists for this case?
Code:
 myScript.sh >nohup_$(date +%Y%m%d%H%M%S).out

Smilie No. nohup / myscript.sh don't open the file -- your shell does, before anything else is even run. They just use the file you opened for them.
This User Gave Thanks to Corona688 For This Post:
kchinnam
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