Network exploration tool and security / port scanner

-iL inputfilename (Input from list) .
    Reads target specifications from inputfilename. Passing a huge list of hosts is often awkward on the
    command line, yet it is a common desire. For example, your DHCP server might export a list of 10,000
    current leases that you wish to scan. Or maybe you want to scan all IP addresses except for those to
    locate hosts using unauthorized static IP addresses. Simply generate the list of hosts to scan and
    pass that filename to Nmap as an argument to the -iL option. Entries can be in any of the formats
    accepted by Nmap on the command line (IP address, hostname, CIDR, IPv6, or octet ranges). Each entry
    must be separated by one or more spaces, tabs, or newlines. You can specify a hyphen (-) as the
    filename if you want Nmap to read hosts from standard input rather than an actual file.

    The input file may contain comments that start with # and extend to the end of the line.

-sL (List Scan) .
    The list scan is a degenerate form of host discovery that simply lists each host of the network(s)
    specified, without sending any packets to the target hosts. By default, Nmap still does reverse-DNS
    resolution on the hosts to learn their names. It is often surprising how much useful information
    simple hostnames give out. For example, fw.chi is the name of one company´s Chicago firewall.  Nmap
    also reports the total number of IP addresses at the end. The list scan is a good sanity check to
    ensure that you have proper IP addresses for your targets. If the hosts sport domain names you do not
    recognize, it is worth investigating further to prevent scanning the wrong company´s network.

    Since the idea is to simply print a list of target hosts, options for higher level functionality such
    as port scanning, OS detection, or ping scanning cannot be combined with this. If you wish to disable
    ping scanning while still performing such higher level functionality, read up on the -PN (skip ping)
    option.

-n (No DNS resolution) .
    Tells Nmap to never do reverse DNS resolution on the active IP addresses it finds. Since DNS can be
    slow even with Nmap´s built-in parallel stub resolver, this option can slash scanning times.

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).

print lines matching a pattern

grep searches the named input FILEs (or standard input if no files are named, or if a single hyphen-minus
(-) is given as file name) for lines containing a match to the given PATTERN.  By  default,  grep  prints
the matching lines.

pattern-directed scanning and processing language

read from standard input and write to standard output and files

Copy standard input to each FILE, and also to standard output.

If a FILE is -, copy again to standard output.