# Bash trap command

> Source: https://learn-bash.net/bash-trap-command/
> Part of Learn Bash, free to read.

It often comes the situations that you want to catch 
a special signal/interruption/user input in your script 
to prevent the unpredictables.

Trap is your command to try:

  - `trap  `

###Example

```bash
#!/bin/bash
# traptest.sh
# notice you cannot make Ctrl-C work in this shell, 
# try with your local one, also remeber to chmod +x 
# your local .sh file so you can execute it!

trap "echo Booh!" SIGINT SIGTERM
echo "it's going to run until you hit Ctrl+Z"
echo "hit Ctrl+C to be blown away!"

while true        
do
    sleep 60       
done
```

Surely you can substitute the `"echo Booh!"` with a function:

```bash
function booh {
	echo "booh!"
}
```

and call it in trap:

```bash
trap booh SIGINT SIGTERM
```

Some of the common signal types you can trap:

  - `SIGINT`: user sends an interrupt signal (Ctrl + C)

  - `SIGQUIT`: user sends a quit signal (Ctrl + C)

  - `SIGFPE`: attempted an illegal mathematical operation

You can check out all signal types by entering the following command:

```bash
kill -l
```

Notice the numbers before each signal name, you can use that number to avoid typing long strings in trap:

```bash
#2 corresponds to SIGINT and 15 corresponds to SIGTERM
trap booh 2 15
```

one of the common usage of trap is to do cleanup temporary files:

```bash
trap "rm -f folder; exit" 2
```