Question

Why do the following lines print only once the files in the current directory (and not three times)?

This is a question from an exam. If you know some source to read about it, it will be great

cp /bin/ls blah
cat blah blah blah >bbb
chmod u+x bbb
bbb

Answer 1

You would need something like:

cp /bin/ls/blah .
cat blah blah blah >bbb
chmod u+x bbb
./bbb

The first difference is the number of parameters to cp. You need to specify the destination as well as the source. The second difference is that unless you have the current directory in the path, you need to use ./command instead of just command to execute a program residing in the current directory.

Besides that, it would important to know what is the content of /bin/ls/blah. If that file is a bash script containing something like:

#!/bin/ls
ls

the modified block of code given at the beginning of this answer will work as expected (printing 3 times the contents of the current directory). If the file is a binary file, it most probably would not work, since you cannot concatenate binary files and expect the resulting file to behave as 3 sequential executions of the original binary file.

UPDATE: After your edit, the answer clearly changes. Now, only the last part applies to it. Since /bin/ls is a binary file, you cannot concatenate binary files and expect the resulting file to behave as 3 sequential executions of the original binary file. If instead of a binary file you were using a script the example would work, though.