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I have a bash script that I want to globally enable set -e.
But rather than disable it and reenable it all the time, I'm wondering if there is a way of selectively disabling error handling just sometimes. For example, commands run from systemd can be preceeded by a minus to ignore errors. Does bash has an equivalent?
e.g.
#!/bin/bash
set -e
WAN_IF=eth2
# Ignore error on next line
tc qdisc del dev ${WAN_IF} root
# I want errors to stop the script on this line
tc qdisc add dev ${WAN_IF} root handle 1: htb default 10
...
etc
Because of the need to enable/disable a lot I don't want to have to keep doing the following:
set +e
tc qdisc del dev ${WAN_IF} root
# I want errors to stop the script on this line
set -e
tc qdisc add dev ${WAN_IF} root handle 1: htb default 10
...
749
Use the INSERT IGNORE command rather than the INSERT command. If a record doesn't duplicate an existing record, then MySQL inserts it as usual. If the record is a duplicate, then the IGNORE keyword tells MySQL to discard it silently without generating an error.
If you want the query to return only unique rows, use the keyword DISTINCT after SELECT . DISTINCT can be used to fetch unique rows from one or more columns. You need to list the columns after the DISTINCT keyword.
The SQL DISTINCT keyword, which we have already discussed is used in conjunction with the SELECT statement to eliminate all the duplicate records and by fetching only the unique records.
Yes, we can ignore duplicate rows in COUNT using DISTINCT.
Add || : (or anything else that is guaranteed not to fail but that's the simplest) to the end of the command.
Though many people would simply tell you that set -e isn't worth it because it isn't as useful as you might think (and causes issues like this) and manual error checking is a better policy.
(I'm not in that camp yet though the more I run into issues like this the more I think I might get there one day.)
From thatotherguy's comment explaining one of major the issues with set -e:
The problem with
set -eisn't that you have to be careful about which commands you want to allow to fail. The problem is that it doesn't compose. If someone else reads this post and usessource yourfile || :to source this script while allowing failure, suddenlyyourfilewill no longer stop on errors anywhere. Not even on failing lines after an explicitset -e.
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