---
tags:
  - Linux
---

## Use `&` to send a process to background

Here is a dummy [process](./Processes.md):

```sh
bash -c 'while sleep 5; do echo "Still running... $(date +%T)"; done'
```

If I run this normally, it will continue to print every 5 seconds and I can't
use the terminal.

If I append `&` it will run in the background:

```sh

bash -c 'while sleep 5; do echo "Still running... $(date +%T)"; done' &
# [1] 13134
```

It prints the job number (`[1]`) and the PID of the process.

Now `stdout` will continue to interrupt every 5 seconds but I can do other
things in the foreground, e.g:

```
 ~ bash -c 'while sleep 5; do echo "Still running... $(date +%T)"; done' &
[2] 13505
➜  ~ Still running... 18:20:42
echo 'i can still use terminal'
i can still use terminal
➜  ~ Still running... 18:20:47
Still running... 18:20:47
```

> Notice now I have two processes running (the same print script, twice), so the
> job number has incremented to `[2]`

## Bring a background process back to the foreground

Use `%<job-number>` or `%<pid` to bring a process back to the foreground:

```sh

fg %1
# [1]  - 13134 running    bash -c 'while sleep 5; do echo "Still running... $(date +%T)"; done'
# Still running... 18:23:22
# Still running... 18:23:22
# Still running... 18:23:27
```

Now it's back in the foreground and I cannot use the terminal:

```
Still running... 18:24:17
ls
Still running... 18:24:22
Still running... 18:24:22
```

## Pausing a job

`Ctrl+Z` does not kill the process. It _pauses_ it. This moves it to the
background and pauses its execution, returning terminal control back to you.

For example I've stopped `vim` below:

```
vim minicom.log
[1]  + 14231 suspended  nvim minicom.log
```

Again I'm given the job number.

For it to continue in the background:

```sh
bg %1
```

Or the foreground:

```sh
fg %1
```

(This will reopen `vim`.)

## Terminate a job

```
kill %1
```

## View jobs with `jobs`

```
jobs
[1]  + suspended  nvim minicom.log
[2]  - running    bash -c 'while sleep 5; do echo "Still running... $(date +%T)"; done'
```