I have a myfile which contains lines like
#!/usr/bin/env python3
print("Hello world")
names = ('${(j:', ':)ZSH_VAR[@]}', )
I would like to pre-process this file with the environment variables in my loaded shell (zsh in my case, but a generic bash solution would also work nicely).
How can I do the equivalent of
$ declare -ga ZSH_VAR=( 1 2 3 )
$ preprocess < myfile
Such that the output is
#!/usr/bin/env python3
print("Hello world")
bar=('1', '2', '3', )
You can use eval for that purpose.
$ BAR=1234 FOO=abcd; while read -r line; do eval 'echo "'"$line"'"'; done < "file"
Or in script. (script.sh)
#!/bin/bash
while read -r line; do eval 'echo "'"$line"'"'"; done < "file"
# If you want to redirect the output into a file (out.txt).
# while read -r line; do eval 'echo "'"$line"'" >> out.txt'; done < "file"
# Or this
# while read -r line; do eval 'echo "'"$line"'"'; done < "file" > out.txt
Then call the script like this:
FOO=abcd BAR=1234 ./script.sh
Note
BE CAREFUL. MAKE SURE YOUR FILE DOES NOT CONTAINS rm commands. JUST TO BE SAFE.
envsubst instead; no chance of a $(rm -rf ~) in your file destroying your home directory.eval, better to use eval 'echo "'"$line"'"' so you don't have a line containing * HELLO * replace the *s with lists of filenames, or changing tabs to spaces, or deleting leading tabs, or so forth. Which is to say, as currently written, this answer has quite a lot of unexpected/undesired behaviors.IFS= before the read in the link showing the fixed version -- that stops read from deleting leading and trailing whitespace before it even gets into the line variable!)
envsubst?eval 'bar="$BAR"'ordeclare 'bar="$BAR"'?