script install_db4.sh check for `patch` command before continuing to install db4 #23579

First contribution. I've read the CONTRIBUTING guide and hope I'm doing this correctly, but please kindly point out anything I should do differently.

I found while running the contrib/install_db4.sh patch that it would fail suddenly with "patch: command not found". I'd rather see it fail early before doing any work, allow me to install the patch command, and then run again. (CentOS Linux) Here's a PR proposed to fix it.

error message:

...
db-4.8.30.NC/txn/txn_rec.c
db-4.8.30.NC/txn/txn_region.c
db-4.8.30.NC/txn/txn_stat.c
db-4.8.30.NC/txn/txn_util.c
./contrib/install_db4.sh: line 71: patch: command not found

"./contrib/install_db4.sh: line 71: patch: command not found" is not obscure enough to need an improvement. NAK.

Wouldn't it be best to remove this script? We already have depends, which can build bdb4.

@katesalazar not looking for an adjustment to the message; only to check dependencies before starting write operations -- at least for new users like myself who may not have everything installed yet.

For reference, I was following this doc: https://github.com/bitcoin/bitcoin/blob/master/doc/build-unix.md#berkeley-db

Concept ACK, thanks for your contribution.

Wouldn't it be best to remove this script? We already have depends, which can build bdb4.

The depends framework doesn't work on all the platforms that this script works, IIRC. Think of the BSDs. Also it's a simple command to run, nothing to figure out. If we want to encourage people to use depends for this we should document a command that builds only berkeleydb and provides it to the build.

Code review and tested ACK 7bb8eb0bc352b47ee962283898f9becbb4f36c62