-i [command]
The -i (simulate initial login) option runs the shell specified by the password database
entry of the target user as a login shell. This means that login-specific resource files
such as .profile or .login will be read by the shell. If a command is specified, it is
passed to the shell for execution via the shell's -c option. If no command is specified, an
interactive shell is executed. sudo attempts to change to that user's home directory before
running the shell. The security policy shall initialize the environment to a minimal set of
variables, similar to what is present when a user logs in. The Command Environment section
in the sudoers(5) manual documents how the -i option affects the environment in which a
command is run when the sudoers policy is in use.
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-P The -P (preserve group vector) option causes sudo to preserve the invoking user's group
vector unaltered. By default, the sudoers policy will initialize the group vector to the
list of groups the target user is in. The real and effective group IDs, however, are still
set to match the target user.
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Pipelines
A pipeline is a sequence of one or more commands separated by one of the control operators | or |&. The
format for a pipeline is:
[time [-p]] [ ! ] command [ [|⎪|&] command2 ... ]
The standard output of command is connected via a pipe to the standard input of command2. This
connection is performed before any redirections specified by the command (see REDIRECTION below). If |&
is used, the standard error of command is connected to command2's standard input through the pipe; it is
shorthand for 2>&1 |. This implicit redirection of the standard error is performed after any
redirections specified by the command.
The return status of a pipeline is the exit status of the last command, unless the pipefail option is
enabled. If pipefail is enabled, the pipeline's return status is the value of the last (rightmost)
command to exit with a non-zero status, or zero if all commands exit successfully. If the reserved word
! precedes a pipeline, the exit status of that pipeline is the logical negation of the exit status as
described above. The shell waits for all commands in the pipeline to terminate before returning a value.
If the time reserved word precedes a pipeline, the elapsed as well as user and system time consumed by
its execution are reported when the pipeline terminates. The -p option changes the output format to that
specified by POSIX. When the shell is in posix mode, it does not recognize time as a reserved word if
the next token begins with a `-'. The TIMEFORMAT variable may be set to a format string that specifies
how the timing information should be displayed; see the description of TIMEFORMAT under Shell Variables
below.
When the shell is in posix mode, time may be followed by a newline. In this case, the shell displays the
total user and system time consumed by the shell and its children. The TIMEFORMAT variable may be used
to specify the format of the time information.
Each command in a pipeline is executed as a separate process (i.e., in a subshell).
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