Use of shell scripts & and 𞓜

• If the previous instruction is executed correctly , stay Linux One will be sent back in the $?=0 Value

example 1: Judge whether the file exists , Create another file if it exists

ls /tmp/abc && touch /tmp/abc/hehe

example 2: Judge whether the file exists , There is no creation , Being doesn't do anything

ls /tmp/abc || touch /tmp/abc

example 3: Judge whether the file exists , There is a display "exist", There is no display "not exist"

# When there are multiple instructions, execute them in sequence , The latter one is based on the former one $? perform 
ls /tmp/vbirding && echo "exist" || echo "not exist"

# No display ls Output result 
ls 1.txt >/dev/null 2>&1 && echo "exist" || echo "not exist"