Script that outputs the total number of lines in all the text files that are passed as arguments

Question

So I'm working on a script that will accept arguments that are text files, and should output the total number of lines in those files.  For example, if I say

./myScript file1 file2 file3

it will print

10 total

(let us assume that the sum of all the lines from those three files is 10).

I know how to go over all the arguments.  I also know that, to get the number of lines in a file, I would say:

wc -l < fileName

However, how can I make that into an "int" that I can add to some sort of cumulative sum?

Answer 1

You can accomplish your goal simply by using cat and a pipeline:

cat "$@" | wc -l

If you really wanted to sum manually, you can do this with awk:

for f in "$@"; do 
    wc -l < "$f"
done | awk '{ sum+=$1 } END { print sum }'

Or if you really wanted to parse the last line of wc, removing the string "total":

wc -l "$@" | awk 'END { print $1 }'

Answer 2

Building on jordanm’s answer:

1. Pipe all the data through a single instance of wc -l

if [ "$#" -gt 0 ]
then
    cat -- "$@" | wc -l
else
    echo 0
fi

or
 

cat -- /dev/null "$@" | wc -l

• Use -- "$@" to guard against filenames beginning with -.
• Avoid invoking cat with no arguments, as that will cause it to read the standard input.
• Note that cat a_single_file | something is the classic form of the dreaded Useless Use of Cat, but cat one_or_more_file(s) | something can be OK (although it’s still not ideal).

2. Rely on the fact that wc issues a “total” line

if [ "$#" -gt 0 ]
then
    wc -l -- /dev/null "$@" | tail -1
else
    echo 0 total
fi

or
 

wc -l -- /dev/null /dev/null "$@" | tail -1

• Note that wc issues a total line only if it has at least two filename arguments.

3. Use awk without using wc

if [ "$#" -gt 0 ]
then
    awk 'END {print NR}' -- "$@"
else
    echo 0
fi

or
 

awk 'END {print NR}' -- /dev/null "$@"

Warning:

The above commands will not all produce the same answer if any of the files end with a character other than newline.

Answer 3

sed -ne\$= files...

Just hand sed as many filenames as you want in place of files... and, when it has read all of them, it will report the =line-number of the very $last in its input.