1)
head -n1 calories.csv > /tmp/calories
tail -n+2 calories.csv | cut -d\; -f1 | tr -s "[:print:]" "-" > /tmp/prvni
tail -n+2 calories.csv | cut -d\; -f2- > /tmp/zbytek
paste -d\; /tmp/prvni.elk /tmp/zbytek.elk >> /tmp/calories
mv /tmp/calories calories.csv

2)
cut -d: -f1,3 /etc/passwd

3)
cut -d, -f6 ip-by-country.csv | tail -n+2 |  tr -d \" | sort | uniq | wc -l

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caste chyby:

v paste nepouzitie deliaceho znaku (-d \; ) resp. pouzitie '-' ako del. zn.
pozor aby ste nezaratali hlavickovy riadok do vysledku!

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tip:

| sort | uniq |  ... je to iste ako ... | sort -u |

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malickosti:

v 1. premazanie aj prveho riadku

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vzorove riesenie: Lukas K., Michal H., Antonin K.

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Xtra-men:

Pavel Z. (pouzitie --complement -c v cut)
cat calories.csv | cut -f 1 -d \; --complement > tmp2

Nguyen T. Q. (pouzitie viacerych prepinacov v tr)
tr -s -c "\n" "-" (udela to same ako tr -s "[:print:]" "-"

Michal H. (pouzitie sed na pridanie "-;" ako prveho stlpca)
sed -i 's#^#-;#' calories-other.csv

Anetta S. (pouzitie sed na cely priklad 1)
cat calories.csv | sed s/^[^\;]*\"\;/-\;/

Jaroslav V. (pouzitie sed na 3)
cut -f6 -d\, ip-by-country.csv > zeme
sed '1d' zeme | sort -u | wc -l