line(records) Count and grep together in a one command on a dat file

Question

I want to do a line count and get the number into a variable in a shell script. For eg.

 wc -l filename.dat

gives 221 filename.dat I want to grep '221' into a variable, which I could use later. Can this be done in a single statement ? I don't want to copy the output of wc -l into another file and then grep.

Answer 1

You can pass the filename to the STDIN of wc to get only the number of lines :

wc -l <filename.dat

To save it as a variable :

var="$(wc -l <filename.dat)"

Example :

$ wc -l foo.txt 
12 foo.txt

$ wc -l <foo.txt 
12

$ var="$(wc -l <foo.txt)"

$ echo "$var"
12

Note that as Stéphane Chazelas has pointed out, some wc variants might add spaces before and after the number of lines to get desired alignment.