I just learned a really good bash trick which is something I've wanted to have but didn't really appreciate that it was possible so I never even searched for it.

set -ex

Ok, one thing at a time.

set -e

What this does, at the top of your bash script is that it exits as soon as any line in the bash script fails.
Suppose you have a script like this:

git pull origin master
find . | grep '\.pyc$' | xargs rm

If the first line fails you don't want the second line to execute and you don't want the third line to execute either. The naive solution is to "and" them:

git pull origin master && find . | grep '\.pyc$' | xargs rm && ./restart_server.sh

but now it's just getting silly. (and is it even working?)

What set -e does is that it exists if any of the lines fail.

set -x

What this does is that it prints each command that is going to be executed with a little plus.
The output can look something like this:

+ rm -f pg_all.sql pg_all.sql.gz
+ pg_dumpall
+ apack pg_all.sql.gz pg_all.sql
++ date +%A
+ s3cmd put --reduced-redundancy pg_all.sql.gz s3://db-backups-peterbe/Sunday/
pg_all.sql.gz -> s3://db-backups-peterbe/Sunday/pg_all.sql.gz  [part 1 of 2, 15MB]
 15728640 of 15728640   100% in    0s    21.22 MB/s  done
pg_all.sql.gz -> s3://db-backups-peterbe/Sunday/pg_all.sql.gz  [part 2 of 2, 14MB]
 14729510 of 14729510   100% in    0s    21.50 MB/s  done
+ rm pg_all.sql pg_all.sql.gz

...when the script looks like this:

set -ex
rm -f pg_all.sql pg_all.sql.gz
pg_dumpall > pg_all.sql
apack pg_all.sql.gz pg_all.sql
s3cmd put --reduced-redundancy pg_all.sql.gz s3://db-backups-peterbe/`date +%A`/
rm pg_all.sql pg_all.sql.gz

And to combine these two gems you simply put set -ex at the top of your bash script.

Thanks @bramwelt for showing me this one.

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