How to prevent sed to destroy your symlinks

Because of EBS, we have a subdirectory in our $TNS_ADMIN which has the following name

PDB1_test1.oric.no

In other words, the files listener.ora, sqlnet.ora and tnsnames.ora are symlinks pointing to this subdirectory:

# ls -altr
lrwxrwxrwx  1 oracle dba   34 Feb 10 13:29 sqlnet.ora -> PDB1_test1.oric.no/sqlnet.ora
lrwxrwxrwx  1 oracle dba   36 Feb 10 13:29 tnsnames.ora -> PDB1_test1.oric.no/tnsnames.ora
lrwxrwxrwx  1 oracle dba   36 Feb 18 12:17 listener.ora -> PDB1_test1.oric.no/listener.ora
drwxr-xr-x  2 oracle dba 4096 Feb 18 12:18 PDB1_test1.oric.no
drwxr-xr-x  5 oracle dba 4096 Feb 18 12:19 .

If you are to exchange a string in these files, for example when switching to a new version of the Oracle software, make sure you use the directive --follow-symlinks to preserve your symlinks:

export PRE_ORACLE_VERSION=19.17
export NEW_ORACLE_VERSION=19.18
cd $TNS_ADMIN
sed --follow-symlinks -i "s/$PRE_ORACLE_VERSION/$NEW_ORACLE_VERSION/g" listener.ora

If you don't, the listener.ora will be placed directly in $TNS_ADMIN, and the symlinks will be dropped.