Dynamically substitue pattern with env variable with bash [duplicate] - regex

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Replace a string in shell script using a variable
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I have a file file.txt with this content: Hi {YOU}, it's {ME}
I would like to dynamically create a new file file1.txt like this
YOU=John
ME=Leonardo
cat ./file.txt | sed 'SED_COMMAND_HERE' > file1.txt
which content would be: Hi John, it's Leonardo
The sed command I tried so far is like this s#{\([A-Z]*\)}#'"$\1"'#g but the "substitution" part doesn't work correctly, it prints out Hi $YOU, it's $ME

Answer 1

The sed utility can do multiple things to each input line:
$ sed -e "s/{YOU}/$YOU/" -e "s/{ME}/$ME/" inputfile.txt >outputfile.txt
This assumes that {YOU} and {ME} occurs only once each on the line, otherwise, just add g ("s/{YOU}/$YOU/g" etc.)

Answer 2

You can use awk with 2 files.
$> cat file.txt
Hi {YOU}, it's {ME}
$> cat repl.txt
YOU=John
ME=Leonardo
$> awk -F= 'FNR==NR{a["{" $1 "}"]=$2; next} {for (i in a) gsub(i,a[i])}1' repl.txt file.txt
Hi John, it's Leonardo
First awk command goes through replacement file and stores each key-value in an array a be wrapping keys with { and }.
In second iteration we just replace each key by value in actual file.
Update:
To do this without creating repl.txt you can use `process substitution**:
awk -F= 'FNR==NR{a["{" $1 "}"]=$2; next} {
for (i in a) gsub(i,a[i])} 1' <(( set -o posix ; set ) | grep -E '^(YOU|ME)=') file.txt