UNIX for Dummies Questions & Answers

touch a
touch b
# cause copy to fail by preventing it writing to b
chmod 000 b

if cp a b
then
        echo "Copied file"
else
        echo "File not copied!"
fi

function die
{
        echo "$@" >&2
        exit 1
}

cp a b || die "Couldn't copy file!"

cp file1 file2
if [ $? -eq 0 ]
then
  echo "Copy was successful"
else
  echo "Copy was unsuccessful"
fi

$ cp file1 file2
$ echo $?

Every command return exit status (sometimes referred to as a return status or exit code). A successful command returns a 0, while an unsuccessful one returns a non-zero value that usually can be interpreted as an error code. Well-behaved UNIX commands