Redir/pipes

Question 1

STDIN

Answer 1

Standard input
0

Question 2

What will this do?
~~~
python hello.py < foo.txt
~~~

Answer 2

feed foo.txt to stdin for python

Question 3

STDOUT

Answer 3

Standard Out
1

Question 4

python hello.py > output.txt

Answer 4

stdout to (file)

Question 5

python hello.py >> output.txt

Answer 5

stdout to (file), append

Question 6

STDERR

Answer 6

Standard Error
2

Question 7

python hello.py 2> error.log

Answer 7

stderr to (file)

Question 8

python hello.py 2>&1

Answer 8

stderr to stdout

Question 9

python hello.py 2>/dev/null

Answer 9

stderr to (null)

Question 10

python hello.py >output.txt 2>&1

Answer 10

stdout and stderr to (file), equivalent to &>

Question 11

python hello.py &>/dev/null

Answer 11

stdout and stderr to (null)

Question 12

echo "$0: warning: too many users" >&2

Answer 12

print diagnostic message to stderr

Question 13

diff <(ls -r) <(ls)

Answer 13

Compare two stdout without files