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Redirect output to the same input file in awk

 
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Top Forums UNIX for Dummies Questions & Answers Redirect output to the same input file in awk
# 22  
Old 02-26-2015
Quote:
Originally Posted by stew
I am okay with your code, but my concern is move command. shall we use
Code:
cp sysctl.conf.mod sysctl.conf

rather than
Code:
mv sysctl.conf.mod sysctl.conf

Why? Do you need to leave two copies of the file around when a change is made?
# 23  
Old 02-27-2015
No, I am not gonna leave the
Code:
sysctl.conf.mod

on the same directory, at the end will rm sysctl.conf.mod file. I always prefer
Code:
cp

instead of
Code:
mv

if want to copy the content of the file.

Please let me know if any have thoughts
# 24  
Old 02-27-2015
Quote:
Originally Posted by stew
No, I am not gonna leave the
Code:
sysctl.conf.mod

on the same directory, at the end will rm sysctl.conf.mod file. I always prefer
Code:
cp

instead of
Code:
mv

if want to copy the content of the file.

Please let me know if any have thoughts
You need to use cp and rm if:
  1. there are multiple hard links to the file you are overwriting,
  2. you need to preserve file modes that might be different from what would be set using your current file mode creation mask (see umask()), or
  3. the owner and group IDs of the file need to be preserved and you are running with a different user ID or primary group ID than are on the file you're overwriting.
Otherwise, mv is preferred because it is an atomic operation that always leaves you with either the old file contents or the (complete) new file contents as the contents of the target file. When you use cp instead of mv (from a file in the same filesystem), there will be a (hopefully short) period of time when the target file is contains a (possibly empty) subset of the contents that the file should contain. If the file is read during this time period, the incomplete contents of your configuration file could generate unexpected side effects.

Just using cp without following successful invocations with rm leaves you with two copies of the file.
This User Gave Thanks to Don Cragun For This Post:
stew
# 25  
Old 03-02-2015
Don - Thank you so much. code worked perfectly. we can close this issue. If I need any more details on the same will reopen it.
 
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