Concatenate string in a loop of shell script

Question

I want to concatenate a suffix to a string in a loop of shell script, but the result makes me confused. The shell script is as follows:

for i in `cat IMAGElist.txt`
do
  echo $i
  echo ${i}_NDVI
done

The result is:

LT51240392010131BKT01
_NDVI40392010131BKT01
LT51240392010163BKT01
_NDVI40392010163BKT01
...

The front five chars was replaced with "_NDVI". But the expected result should be:

LT51240392010131BKT01
LT51240392010131BKT01_NDVI
LT51240392010163BKT01
LT51240392010163BKT01_NDVI
...

I think the method for string concatenation is right if not in the loop. I don't know why this result is produced?

Tom Fenech · Accepted Answer · 2016-10-07 10:09:12Z

1

It looks as though your file may contain Windows-style line endings (carriage return + line feed), so you should convert them to UNIX-style ones. A simple way to do this is with the tool dos2unix.

Don't use for to read lines of a text file:

while read -r line
do
  echo "$line"
  echo "${line}_NDVI"
done < IMAGElist.txt

Note that you can achieve this result more efficiently with tools designed to process text, such as awk or sed.

edited Oct 7, 2016 at 10:09

answered Oct 7, 2016 at 10:03

Tom Fenech

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2 Comments

Victor Tan Over a year ago

Thank you for your answering! I tried your approach, but the result is the same as the original.

Tom Fenech Over a year ago

I think the issue is probably with the line endings in your input file; I've added to my answer.

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