Counting commas in a line in bash

Question

Sometimes I receive a CSV file which has a carriage return inside a cell. This is not an acceptable format to a program that will use it as input.

In order to detect if an input line is split, I determined that a bad line would not have the expected number of commas in it. Is there a bash or other common unix command line tool that would allow me to count the commas in the line? If necessary, I can write a Python or Perl program to do it, but if possible, I'd like to add a line or two to an existing bash script to cause it to fail if the comma count is wrong. Any ideas?

Answer 1

Strip everything but the commas, and then count number of characters left:

$ echo foo,bar,baz | tr -cd , | wc -c
2

Answer 2

To count the number of times a comma appears, you can use something like awk:

string=(line of input from CSV file)
echo "$string" | awk -F "," '{print NF-1}'

But this really isn't sufficient to determine whether a field has carriage returns in it. Fields can have commas inside as long as they're surrounded by quotes.

Answer 3

In pure Bash:

while IFS=, read -ra array
do
    echo "$((${#array[@]} - 1))"
done < inputfile

or

while read -r line
do
    count=${line//[^,]}
    echo "${#count}"
done < inputfile

Answer 4

What worked for me better than the other solutions was this. If test.txt has:

foo,bar,baz
baz,foo,foobar,bar

Then cat test.txt | xargs -I % sh -c 'echo % | tr -cd , | wc -c' produces

2
3

This works very well for streaming sources, or tailing logs, etc.