https://github.com/sagikazarmark/fsig
Send signals to a subprocess when files change
https://github.com/sagikazarmark/fsig
signal subprocess
Last synced: 6 months ago
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Send signals to a subprocess when files change
- Host: GitHub
- URL: https://github.com/sagikazarmark/fsig
- Owner: sagikazarmark
- License: mit
- Created: 2018-03-12T00:43:24.000Z (over 7 years ago)
- Default Branch: master
- Last Pushed: 2018-09-25T11:40:24.000Z (about 7 years ago)
- Last Synced: 2025-04-09T23:12:41.983Z (6 months ago)
- Topics: signal, subprocess
- Language: Go
- Size: 53.7 KB
- Stars: 16
- Watchers: 3
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
README
# File Signal (fsig)
[](https://travis-ci.org/sagikazarmark/fsig)
[](https://goreportcard.com/report/github.com/sagikazarmark/fsig)
[](https://godoc.org/github.com/sagikazarmark/fsig)
**Send signals to a child process upon file changes**
This project was born because of the need to reload applications upon Kubernetes ConfigMap changes,
but it can be used without the containerization stuff as well.
Fsig is heavily inspired by [configmap-reload](https://github.com/jimmidyson/configmap-reload)
which provides a similar use case for modern application (like Prometheus) run on Kubernetes.
## Usage
```
usage: fsig --watch=WATCH [] [...]
Send signals to a child process upon file changes
Flags:
--help Show context-sensitive help (also try --help-long and --help-man).
-w, --watch=WATCH ... Watched directory (at least one)
--version Show application version.
Args:
Signal to be sent to the child process
Child process command
[] Child process arguments
```
### Example
```bash
$ fsig -w watched/dir HUP -- ./my_program --arg
```
## Installation
Download a precompiled binary for the [latest](https://github.com/sagikazarmark/fsig/releases/latest) version.
### Ubuntu images
```dockerfile
RUN apt-get update && apt-get install -y wget
ENV FSIG_VERSION 0.4.0
RUN wget https://github.com/sagikazarmark/fsig/releases/download/v${FSIG_VERSION}/fsig_${FSIG_VERSION}_linux_amd64.tar.gz \
&& tar -C /usr/local/bin -xzvf fsig_${FSIG_VERSION}_linux_amd64.tar.gz fsig \
&& rm fsig_linux_amd64.tar.gz
```
### Alpine images
```dockerfile
RUN apk add --no-cache openssl
ENV FSIG_VERSION 0.4.0
RUN wget https://github.com/sagikazarmark/fsig/releases/download/v${FSIG_VERSION}/fsig_${FSIG_VERSION}_linux_amd64.tar.gz \
&& tar -C /usr/local/bin -xzvf fsig_${FSIG_VERSION}_linux_amd64.tar.gz fsig \
&& rm fsig_linux_amd64.tar.gz
```
## Alternatives
fsig might not always fit your use case.
The following alternatives provide similar solutions to the problem fsig tries to solve.
### Shell script
**Pros:**
- very simple
- has only two dependencies (`bash`, `inotifywait`)
**Cons:**
- works by putting processes in the background
```bash
#!/bin/bash
{
echo "Starting [APPLICATION]"
start_application "$@"
} &
pid=$!
watches=${WATCH_PATHS:-"/path/to/watched/file"}
echo "Setting up watches for ${watches[@]}"
{
inotifywait -e modify,move,create,delete --timefmt '%d/%m/%y %H:%M' -m --format '%T' ${watches[@]} | while read date time; do
echo "File change detected at ${time} on ${date}"
kill -s HUP $pid
done
echo "Watching file changes failed, killing application"
kill -TERM $pid
} &
wait $pid || exit 1
```
#### Install on Alpine
```bash
$ apk add bash inotify-tools
```
#### Install on Debian
```bash
$ apt-get install bash inotify-tools
```
### Entr
[entr](http://entrproject.org/) is a tool similar to `inotifywait` with the purpose of providing better user
experience when used in scripts.
**Pros:**
- tiny dependency
- very simple usage (compared to the script above)
**Cons:**
- cannot watch directories without exiting first which makes it impossible to use in a Docker container
## License
The MIT License (MIT). Please see [License File](LICENSE) for more information.