Save output of bash command for use with pipe command (|)

Question

Say I have the following problem

Count the files in the folder which have an "a" in the filename
Repeat for "e", "i" and all the other vowels

One solution is:

FilesWithA=$(ls | grep a | wc -l)
FilesWithE=$(ls | grep e | wc -l)
FilesWithI=$(ls | grep i | wc -l)
FilesWithO=$(ls | grep o | wc -l)
FilesWithU=$(ls | grep u | wc -l)

This works fine, but the folder contains many thousands of files. I'm looking to speed this up by capturing the output of ls in a variable, then sending the output to grep and wc, but the syntax is defeating me.

lsCaptured=$(ls)
FilesWithA=$($lsCaptured | grep a | wc -l) #not working!

Possible duplicate of Capturing multiple line output into a Bash variable, or How to preserve line breaks when storing a command output to a variable in bash — oguz ismail
– oguz ismail, Commented Dec 11, 2019 at 23:26
@oguzismail: None of those gave the <<< or here-string operator, which worked for me. — AlainD
– AlainD, Commented Dec 14, 2019 at 11:12

Gilles Quénot · Accepted Answer · 2019-12-11 22:13:53Z

2

Use this :

#!/bin/bash

captured="$(printf '%s\n' *)"
filesWithA=$(grep -c a <<< "$captured")

Notes :

<<< is a here-string
please, thanks to not parsing ls output

edited Dec 11, 2019 at 22:13

answered Dec 11, 2019 at 21:50

Gilles Quénot

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2 Comments

Socowi Over a year ago

grep has the -c option for counting -- no need for wc.

AlainD Over a year ago

Awesome, thanks! Just what I needed. The answers suggested in a comment were not helpful. Note that you can insert the here-string even in more complex commands such as FilesWithA=$(grep a <<< "$captured" | wc -l).

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