Show help & version info

Like other commands in Unix-like Operating Systems, “-h/--help“ prints help information: 

  1. # tcpdump -h
  2. tcpdump version 4.9.2
  3. libpcap version 1.9.0-PRE-GIT (with TPACKET_V3)
  4. LibreSSL 2.8.3
  5. Usage: tcpdump [-aAbdDefhHIJKlLnNOpqStuUvxX#] [ -B size ] [ -c count ]
  6.                 [ -C file_size ] [ -E algo:secret ] [ -F file ] [ -G seconds ]
  7.                 [ -i interface ] [ -j tstamptype ] [ -M secret ] [ --number ]
  8.                 [ -Q in|out|inout ]
  9.                 [ -r file ] [ -s snaplen ] [ --time-stamp-precision precision ]
  10.                 [ --immediate-mode ] [ -T type ] [ --version ] [ -V file ]
  11.                 [ -w file ] [ -W filecount ] [ -y datalinktype ] [ -z postrotate-command ]
  12.                 [ -Z user ] [ expression ]

While --version shows tcpdump‘s version: 

  1. # tcpdump --version
  2. tcpdump version 4.9.2
  3. libpcap version 1.9.0-PRE-GIT (with TPACKET_V3)
  4. LibreSSL 2.8.3