I really do love aliases. I mean:
Off late I've been using docker a lot, and I find myself running these two commands often:
Now that's a lot of characters - and I also really hate having to hit the spacebar - introduces even more scope for typos.
So I wanted to alias them to
The first one is straight forward. It can even just be a shell alias like
alias dps='docker ps -a', but generally I prefer to keep them as tiny utilities in my
dsh, this one has some dynamic-ness to it. So here's the spec:
- Ability to specify the container name or ID
- Ability to specify command to run, but default to running
bashsince that is the most common use case.
Here's the 5-second solution:
(i.e. compromise by skipping half the spec)
#!/bin/bash docker exec -it $1 $2
This works to some extent - the first argument is the tag, and the second is the command, but it doesn't gracefully fallback to using
bash as the default. Also, this only works for one-word commands as arguments since we are using
$2 and not
$@ - but that is easily fixed even in the 5-second solution.
Now we could assign
cmd=bash and then with check if
$2 exists in an
if condition and overwrite
const cmd = ARGV || "bash" .
Enter Shell Parameter Expansion
(a.k.a the 20mins + write a blog post time solution)
Yeah that's a mouthful. As with most things to do with shell scripting - we're about to type a bunch of gibberish.
If parameter is unset or null, the expansion of word is substituted. Otherwise, the value of parameter is substituted.
With some experimenting, I found that this works just fine:
I'm often using it like:
❯ dsh web # => Enter bash shell at container web ❯ dsh alpine1 ash # => Enter ash shell at container alpine1 ❯ dsh alpine1 ping -c 1 google.com PING google.com (126.96.36.199): 56 data bytes 64 bytes from 188.8.131.52: seq=0 ttl=37 time=11.380 ms --- google.com ping statistics --- 1 packets transmitted, 1 packets received, 0% packet loss round-trip min/avg/max = 11.380/11.380/11.380 ms
You can find my repository of tiny bin utilities over at github.com/vyder/bin