How can one pipe a random string to sed for substitution in a file?

Question

I've tried this:

echo $RANDOM | md5sum | head -c 20 | { read val; sed -i 's/__SALT__/$val/g' app.txt; }

But this replaces __SALT__ with the string $val instead of the value in the variable.

Do note there are only 32768 possible values for salt in this case... — frostschutz, Jan 24 '22 at 21:58
if you want a sensible salt, you should read /dev/urandom instead of using the shell's $RANDOM. For a random 80-bit salt, you could use head -c10 /dev/urandom | md5sum | head -c20. (Or something with od to make the hexdump, since getting the MD5 hash of a random byte string is pretty much unnecessary.) — ilkkachu, Jan 24 '22 at 22:22

score 0 · Answer 1 · answered Jan 24 '22 at 21:53

0

Just needs double quotes:

echo $RANDOM | md5sum | head -c 20 | { read val; sed -i "s/__SALT__/$val/g" app.txt; }

answered Jan 24 '22 at 21:53

geoidesic

1 Answers1