Bash script generates line break - Why?

Question

I made a small bash script which gets the current air pressure from a website and writes it into a variable. After the air pressure I would like to add the current date and write everything into a text file. The target should be a kind of CSV file.

My problem. I always get a line break between the air pressure and the date. Attempts to remove the line break by sed or tr '\n' have failed.

2nd guess from me: wget is done "too late" and echo is already done.

So I tried it with && between all commands. Same result.

Operating system is Linux. Where is my thinking error?

I can't get any further right now. Thanks in advance.

Sven

PS.: These are my first attempts with sed. This can be written certainly nicer ;)

#!/bin/bash

luftdruck=$(wget 'https://www.fg-wetter.de/aktuelle-messwerte/' -O aktuell.html && cat aktuell.html | grep -A 0 hPa | sed -e 's/<[^>]*>//g' | sed -e '/^-/d' | sed -e '/title/d' | sed -e 's/ hPa//g')

datum=$(date) 

echo -e "${luftdruck} ${datum}"  >> ausgabe.txt

Btw.: you can replace aktuell.html && cat aktuell.html with a -. — Cyrus
– Cyrus, Commented Oct 21, 2022 at 19:19
The use of echo -e is a bug here; you want simply echo, or printf — tripleee
– tripleee, Commented Oct 21, 2022 at 19:24
&& doesn't have anything to do with this; && means "run the next command only if the first command succeeds". In this case, the && is actually appropriate (it shouldn't try to use the file if it wasn't downloaded successfully), but for reasons that have nothing at all to do with the problem you're trying to solve. — Gordon Davisson
– Gordon Davisson, Commented Oct 21, 2022 at 19:44
Btw: You can combine sed -e ... | sed -e ... into sed -e ... -e ... or sed -e '...; ...'. It is not only shorter, but also way faster (even though it does not really matter in this case). — Socowi
– Socowi, Commented Oct 21, 2022 at 20:31
Thank you all for your suggestions for improvement @tripleee - the -e was left over from the trial and error - but had neither positive nor negative effects — SPagesDE
– SPagesDE, Commented Oct 21, 2022 at 20:59

Cyrus · Accepted Answer · 2022-10-21 19:20:47Z

2

Replace sed -e 's/ hPa//g') with sed -e 's/ hPa//g' | dos2unix) to replace trailing carriage return (DOS/Windows) with line feed (Unix/Linux).

answered Oct 21, 2022 at 19:20

Cyrus

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1 Comment

SPagesDE Over a year ago

The nearly perfect answer ;)

Socowi · Accepted Answer · 2022-10-21 20:49:41Z

1

The html file you download is using Windows line endings (Carriage Return \r + Line Feed \n). I assume your bash script only removes \ns, but the editor you are using to view the file is showing the \r as a linebreak.

Therefore, you could pipe everything through tr -d \\r\\n which would remove all line breaks.

But there is a better alternative: Extract only the important part instead of whole lines.

luftdruck=$(
    wget 'https://www.fg-wetter.de/aktuelle-messwerte/' -O - |
    grep -o '[^>]*hPa' | tr -dc 0-9.
)
echo "$luftdruck $(date)" >> ausgabe.txt

edited Oct 21, 2022 at 20:49

answered Oct 21, 2022 at 20:42

Socowi

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1 Comment

SPagesDE Over a year ago

The perfect answer ;) And I realized my thinking problem: wget just downloads data and doesn't interpret anything - because it's not a browser and shouldn't be one

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