Question

I’m trying to trim a few lines from a file. I know exactly how many lines to remove (say, 2 from the top), but not how many total lines are in the file. So I tried this straightforward solution:

$ wc -l $FILENAME
119559 my_filename.txt
$ LINES=$(wc -l $FILENAME | awk '{print $1}')
$ tail -n $(($LINES - 2)) $FILENAME > $OUTPUT_FILE

The output is fine, but what happened to LINES??

$ wc -l $OUTPUT_FILE
119557 my_output_file.txt
$ echo $LINES
107

Hoping someone can help me understand what’s going on.

Answer 1

$LINES has a special meaning. It is the number of rows the terminal has, and if you resize your terminal window, it will be re-set. See info "(bash)Bash Variables".