Could someone explain to me "read var1 _ < <(ls -1l | wc -l); echo $var1"

Question

read start _ < <(ls -1l | wc -l); echo $start

In particular:

the underscore after read command
the second minus (<)
how does the "echo $var1" take the value of previous command

The original code:

read start _ < <(du -bcm kali-linux-2016.2-amd64.iso | tail -1); echo $start

I have just simplify the code because i'm interested in the syntax

The `_` is just a regular variable name like `foo`, and is a common name when you don't care about it. As for how a value gets into `var1`, that's what `read` is for. — that other guy, May 29 '19 at 19:33
The command overall is a very brittle and cumbersome way to get the number of files in the current directory. [BashFAQ/004](https://mywiki.wooledge.org/BashFAQ/004) shows the robust best practice. — Benjamin W., May 29 '19 at 19:36
`foo < <(bar)` is basically the same as `bar > tempfile; foo < tempfile` — that other guy, May 29 '19 at 19:44
Try this to understand `read name junk < <(echo fred 46)` then `echo $name` — Mark Setchell, May 29 '19 at 20:11

score 1 · Answer 1 · answered May 29 '19 at 19:29

1

The following should help about the "_": https://unix.stackexchange.com/questions/280453/understand-the-meaning-of

This will about the "<<": https://askubuntu.com/questions/678915/whats-the-difference-between-and-in-bash

please do more research before dumping it on SO to do your work.

and echo generally just repeats what it's told ('echoes' it). "$" is a signifier of variables in shell script, so $var1 is a variable named var1. In order to access any variable, you must prefix it with a '$'

answered May 29 '19 at 19:29

jsarbour

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i still don't understand the syntax code – M C May 29 '19 at 20:02
What do you not understand? Please ask direct questions, and don't just proclaim that you do not understand. Before you ask SO, please ask those questions of google. – jsarbour Jun 03 '19 at 13:00

Could someone explain to me "read var1 _ < <(ls -1l | wc -l); echo $var1"

1 Answers1