Print real and effective user id (uid) and group id (gid), prints identity information about the given user, or if no user is specified the current process.

      id [options]... [username]

By default, it prints the real user id, real group id, effective user id if different from the real user id, effective group id if different from the real group id, and supplemental group ids.

Each of these numeric values is preceded by an identifying string and followed by the corresponding user or group name in parentheses.

   The options cause `id' to print only part of the above information.

     Print only the group id.

     Print only the supplementary groups.

     Print the user or group name instead of the ID number.
     Requires -u, -g, or -G

     Print the real, instead of effective, user or group id.  
     Requires -u, -g, or -G

     Print only the user id.

Related linux commands:

echo – Display message on screen
env – Display, set, or remove environment variables
groups – Print group names a user is in
hostname – Print or set system name
logname – Print current login name
uname – Print system information
users – Print login names of users currently logged in
who – Print who is currently logged in
whoami – Print the current user id and name (`id -un’)
Equivalent Windows command: ECHO %USERNAME%

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