The project I’m working on right now involve not just Dockerized Rails microservices, Meteor JS, and a data set measured in tens of terabytes, but also a big Bash code base.
Bash is a language that makes it easy to shoot yourself in the foot. I have some thoughts on how to write robust, modular, loosely coupled, unit tested Bash that go beyond Bash strict mode and shellcheck. However, let’s save those for later.
Here’s a useful shell command for today: watch
watch will run a command for you every few seconds and output the results on a clean screen. If you combine it with a split-screen or split-pane tool, you can quickly create a mini-dashboard.
For example, watch -n15 df -h will print your free disk space every 15 seconds:
Every 15.0s: df -h Tue Apr 14 13:43:25 2015 Filesystem Size Used Avail Use% Mounted on /dev/sda3 1.8T 691G 1.1T 40% / tmpfs 253G 12K 253G 1% /dev/shm /dev/sda1 248M 58M 178M 25% /boot /dev/sdb1 30T 12T 18T 41% /my_disk
By way of another example, watch -n60 db2 list utilities show detail will check on the status of your DB2 load and other operations every 60 seconds.
Every 60.0s: db2 list utilities show detail Mon Apr 13 12:06:24 2015 ID = 4 Type = LOAD Database Name = MY_DB Member Number = 0 Description = [LOADID: 1177.2015-04-13-188.8.131.522010.0 (20;15)] [*LOCAL.MY_USER.150413204511] OFFLINE LOAD DEL AUTOMATIC INDEXING INSERT NON-RECOVERABLE MY_SCHEMA .MY_TABLE Start Time = 04/13/2015 15:58:12.298788 State = Executing Invocation Type = User Progress Monitoring: Phase Number = 1 Description = SETUP Total Work = 0 bytes Completed Work = 0 bytes Start Time = 04/13/2015 15:58:12.298799 Phase Number [Current] = 2 Description = LOAD Total Work = 4105362974 rows Completed Work = 1069904365 rows Start Time = 04/13/2015 15:58:15.821695 Phase Number = 3 Description = BUILD Total Work = 2 indexes Completed Work = 0 indexes Start Time = Not Started
Mac OS X does not include watch by default. Assuming you have Homebrew, the following will install watch for you:
brew install watch