An example might have been useful, but if I understood you correctly, this would work:

echo "Hello: world" | cut -f1 -d":"

This will convert "hello: world" into "hello".

An example might have been useful, but if I understood you correctly, this would work:

echo "Hello: world" | cut -f1 -d":"

This will convert Hello: world into Hello.

An example might have been useful, but if I understood you correctly, this would work:

cut -f1 -d":"

This will convert "hello: world" into "hello".

An example might have been useful, but if I understood you correctly, this would work:

echo "Hello: world" | cut -f1 -d":"

This will convert "hello: world" into "hello".