Entr overview
Today, I would like to introduce you to the project entr.
I discovered this project randomly a while ago, but I had been searching for a tool
like this for a while.
The goal of this tool is to provide a simple command which can launch
a specified command when some files are modified.
Concretely, this tool can be useful if you are searching for an alternative to
livereload, but not related to a specific language and not related to a full
blown IDE
Example
I often use it to automatically launch tests for Golang projects I am
developping.
Imagine, I wish to test the following function in the
pkg.go
file:
// Inc returns the op1 integer incremented by one unit
func Inc(op1 int) int {
return op1 + 1
}
I wish to test it, with this test in pkg_test.go
:
func Test_Inc(t *testing.T) {
actual := Inc(1)
if actual != 2 {
t.Errorf("Expecting: <2>, got <%d>", actual)
}
}
I would launch my tests continuously with the following command:
find *.go | entr -c -s "go test ."
Here is a live preview of the result (using asciinema):
At first, the test is not working, but as soon as the test file is updated, the
test is launched again.
The specificity here, is to use the -c
flag, in order to clear the screen
before launching the new command.
You can find the full list of options here
How does it work ?
In order to avoid polling,
entr
uses file system events
(kqueue with BSD,
inotify with Linux).
The full source code is available here:
How to get it ?
If you wish to install it, it's really easy, just use your Linux distribution package:
Ubuntu, Debian, Mint, ... :
$ apt install entr
Centos, ... :
$ yum install entr
MacOS :
$ brew install entr
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