File contents:

```
RANDOM TEXT    num1=400    num2=15    RANDOM TEXT
RANDOM TEXT    num1=300    num2=10    RANDOM TEXT
RANDOM TEXT    num1=200    num2=5    RANDOM TEXT

```

I would like to subtract 5 for each num2 per line like so:

```
RANDOM TEXT    num1=400    num2=10    RANDOM TEXT
RANDOM TEXT    num1=300    num2=5    RANDOM TEXT
RANDOM TEXT    num1=200    num2=0    RANDOM TEXT

```

Pure bash is preferred, but no biggie if another GNU tool does it better.