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overwrite only if both files are the same size

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# 1  
Old 08-10-2012
overwrite only if both files are the same size
Dear users,

I've been looking for a way to overwrite files only if both have the same size, how could I do this? any help is very appreciated.

Best regards,

Gery
# 2  
Old 08-10-2012
This is one method to determine if two files have the same size and then act upon it:

Code:
fs1=`wc -c test1`
fs1="${fs1##+([[:space:]])}"
fs1=`echo $fs1 | cut -d ' ' -f1`

fs2=`wc -c test2`
fs2="${fs2##+([[:space:]])}"
fs2=`echo $fs2 | cut -d ' ' -f1`

if ((fs1 != fs2)) then
  echo "files are not equal in size"
else
  echo "files are equal in size"
fi

This User Gave Thanks to spacebar For This Post:
Gery
# 3  
Old 08-11-2012
Thanks spacebar, nice trick, I'll try that Smilie
# 4  
Old 08-11-2012
If available on your system; stat --printf %s filename
will give you the size as recorded in the directory without opening and counting the file's contents.
Last edited by RudiC; 08-11-2012 at 04:02 PM..
This User Gave Thanks to RudiC For This Post:
alister
# 5  
Old 08-11-2012
Agreed, RudiC. stat or even ls would be more efficient (much more so if the file's are large) than reading every byte.

Regards,
Alister
# 6  
Old 08-12-2012
Not knowing what your system is, and what options stat offers, this would do the job running stat only once:
Code:
if [  $(( $(stat --printf "%s - " new  old) 0 )) -eq 0 ]; then echo "equal"; else echo "NOT equal"; fi

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