overwrite only if both files are the same size

Shell Programming and Scripting
1

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

This is one method to determine if two files have the same size and then act upon it:

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
1 Like
3

Thanks spacebar, nice trick, I'll try that :b:

4

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.

1 Like
5

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

Not knowing what your system is, and what options stat offers, this would do the job running stat only once:

if [  $(( $(stat --printf "%s - " new  old) 0 )) -eq 0 ]; then echo "equal"; else echo "NOT equal"; fi