Question

I have a file called “test.txt” like that:

hello world

it is, just a ‘hello world’ string. If I use a perl regex:

perl -pe "s/hello/bye/g" test.txt

it says:

bye world

but if I try to redirect that file to itself:

perl -pe "s/hello/bye/g" test.txt > test.txt

the resulting file is empty. Why? And how can I ‘filter’ a regex over a file?

Answer 1

perl accepts the parameter -i for inplace. With this, you can process a file with a perl program and immediately have it written back.