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extract string from file name between two underscores

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# 1  
Old 07-19-2012
extract string from file name between two underscores


Here is my question,

I need to extract string between two underscores from the filename

for example, filename is

what I want to extract is 300x300.

There are many such files in my directory, so I guess the code should be like:

for file in *1_12;do
NAME= commend to extract string from($file)

# 2  
Old 07-19-2012
one way:
for fname in *1_12
  tmp=$(echo "$fname" | awk -F '_' '{print $4}' )
  echo $newfname

# 3  
Old 07-19-2012
Thanks. Could you explain a little bit about this line
tmp=$(echo "$fname" | awk -F '_' '{print $4}' )

Last edited by Franklin52; 07-19-2012 at 04:16 PM.. Reason: Please use code tags for data and code samples, thank you
# 4  
Old 07-19-2012
awk parses the filename - it uses the underscore character to separate fields. A few shells can also do this, like bash. Field $4 is the one you want, so awk prints the the $4 field. $[field number] is the awk syntax for each field in a file - the default field separator is tab/space. The -F '_' tells awk to use underscore.
This User Gave Thanks to jim mcnamara For This Post:
# 5  
Old 07-19-2012
Yet another way of doing the same thing...
echo "" | sed 's/.*_\([0-9][0-9]*x[0-9][0-9]*\)_.*/\1/'

This User Gave Thanks to shamrock For This Post:
# 6  
Old 07-19-2012
could you also explain a little bit about this line? Thanks!
# 7  
Old 07-19-2012
The sed command looks at a line and filters out only the part that has this pattern "(number)x(number)" punctuated by underscores. So in this pattern

the regex ".*_" is the entire line to the left of the first 300 as is the "_.*" to the right of the second 300. The [0-9][0-9]* filters out only numbers and the "x" and "_" are taken literally...

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