xargs and cut: getting `cut` fields of a csv to bash variable

Question

I am using xargs in conjuction with cut but I am unsure how to get the output of cut to a variable which I can pipe to use for further processing.

So, I have a text file like so:

test.txt:

/some/path/to/dir,filename.jpg
/some/path/to/dir2,filename2.jpg
...

I do this:

cat test.txt | xargs -L1 | cut -d, -f 1,2
/some/path/to/dir,filename.jpg

but what Id like to do is:

cat test.txt | xargs -L1 | cut -d, -f 1,2 | echo $1 $2

where $1 and $2 are /some/path/to/dir and filename.jpg

I am stumped that I cannot seem to able to achieve this..

Answer 1

You may want to say something like:

#!/bin/bash

while IFS=, read -r f1 f2; do
    echo ./mypgm -i "$f1" -o "$f2"
done < test.txt

• IFS=, read -r f1 f2 reads a line from test.txt one by one, splits the line on a comma, then assigns the variables f1 and f2 to the fields.
• The line echo .. is for the demonstration purpose. Replace the line with your desired command using $f1 and $f2.

Answer 2

Try this:

cat test.txt | awk -F, '{print $1, $2}'

From man xargs:

xargs [-L number] [utility [argument ...]]

-L number Call utility for every number non-empty lines read.

From man awk:

Awk scans each input file for lines that match any of a set of patterns specified literally in prog or in one or more files specified as -f progfile.

So you don't have to use xargs -L1 as you don't pass the utility to call.

Also from man awk:

The -F fs option defines the input field separator to be the regular expression fs.

So awk -F, can replace the cut -d, part.

The fields are denoted $1, $2, ..., while $0 refers to the entire line.

So $1 is for the first column, $2 is for the second one.

An action is a sequence of statements. A statement can be one of the following:

print [ expression-list ] [ > expression ]

An empty expression-list stands for $0.

The print statement prints its argument on the standard output (or on a file if > file or >> file is present or on a pipe if | cmd is present), separated by the current output field separator, and terminated by the output record separator.

Put all these together, cat test.txt | awk -F, '{print $1, $2}' would achieve that you want.