# While we can't manipulate users, there is a bunch of commands that
# print information and which are available to us. Let's have a
# look. The first command to check out is called simply ‹w›. Note
# that the command ‹head› as used here discards all but the first 5
# lines of output.

echo output from w
w | head -n 5

# The command prints information about users who are logged on,
# along with commands that they are currently executing. A more
# basic (and more standard) variant is a command called ‹who›, which
# only prints a subset of the info provided by ‹w›. Most notably,
# the currently executed command is missing:

echo
echo output from who
who | head -n 5

# Feel free to experiment with those commands yourself. To learn
# your own username, you can use the command ‹whoami› (who am i?),
# like this:

echo
echo info about the current user
whoami

# To print the list of groups attached to the active session, we can
# use ‹groups›. There can be more than one.

groups

# Finally, the info from the two previous commands, along with some
# extras, can be obtained from ‹id›. Unlike ‹groups›, this tells us
# which group is primary and also gives numeric identifiers for each
# piece of information. The output of ‹id› is meant to be machine
# readable.

id

# The last two commands can be also invoked on other users (i.e. not
# yourself).  This works as follows:

echo
echo info about the user kontr
groups kontr
id kontr

# This is about all the user- and group-related commands that we
# will look at.  Let's have a quick look at ‹passwd.txt› before
# going on to C.