this post was submitted on 24 Oct 2023
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issues with bash commands as variables (monero.town)
submitted 2 years ago* (last edited 2 years ago) by shortwavesurfer@monero.town to c/programming@beehaw.org
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Any ideas? I am attempting to write a script that uses sed.

If done this way it fails

  • rmdec="sed 's/..................$//'"
  • i1xmr=$(echo "$i1p/$apiresponse*1000" |bc -l |$rmdec)

But if i do it this way it works

  • i1xmr=$(echo "$i1p/$apiresponse*1000" |bc -l | sed 's/..................$//')
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[–] bizdelnick@lemmy.ml 1 points 2 years ago* (last edited 2 years ago) (2 children)

And again, using here-document greatly improves readability, like this.

[–] shortwavesurfer@monero.town 1 points 2 years ago (1 children)

Hmm. I had a look at the example given. I see the idea, but would cat be the thing to use or would it be echo <<-EOF > "$file"?

[–] bizdelnick@lemmy.ml 1 points 2 years ago (1 children)

You need cat because it reads stdin and prints it to stdout. echo does not read stdin, it prints its arguments.

[–] shortwavesurfer@monero.town 1 points 2 years ago (1 children)

I have never used cat like that before. If you just ent cat abcd > file it says abcd doesnt exist but does create "file". I know you can cat contents of a file into another file but why the <<-EOF > file works is a bit beyond me.

[–] bizdelnick@lemmy.ml 1 points 2 years ago

cat does not create file, your shell does when you redirect the standard output with > file.

[–] shortwavesurfer@monero.town 1 points 2 years ago (1 children)

Alright, I modified it and formatted it. However, for whatever reason, the output HTML in /var/www/html/index.html does not keep the formatting and is all just left aligned as before. That's not really a problem, just more of a curiosity as to why it did not inherit the formatting of the input.

[–] bizdelnick@lemmy.ml 1 points 2 years ago* (last edited 2 years ago)

When using "<<-", shell removes all tabs from the beginning of each line. So you have to use tabs for formatting inside your script and then spaces for HTML formatting, as in my example. Or use "<<" without dash to preserve tabs.