How can I insert the content of the variable $SALT in a specific point (line or string) of a file like wp-contet.php from wordpress using Bash script?
I'm not an expert at parsing text files in bash but you should delete the lines that define the things you're downloading from the wordpress salt and then insert the variable at the end... something like:
#!/bin/sh
SALT=$(curl -L https://api.wordpress.org/secret-key/1.1/salt/)
STRING='put your unique phrase here'
printf '%s\n' "g/$STRING/d" a "$SALT" . w | ed -s wp-config.php
OK, now it's fixed... it should look for where the salt is supposed to go and it will replace it with the info retrieved from https://api.wordpress.org/secret-key/1.1/salt/