bcc-ttysnoop(8)

1ttysnoop(8)                 System Manager's Manual                ttysnoop(8)
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NAME

6       ttysnoop - Watch output from a tty or pts device. Uses Linux eBPF/bcc.
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SYNOPSIS

9       ttysnoop [-h] [-C] device
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DESCRIPTION

12       ttysnoop  watches  a tty or pts device, and prints the same output that
13       is appearing on that device. It can be used to mirror the output from a
14       shell session, or the system console.
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16       This  works  by  use of kernel dynamic tracing of the tty_write() func‐
17       tion.  This tool will  need  updating  in  case  that  kernel  function
18       changes in a future kernel version.
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20       Since this uses BPF, only the root user can use this tool.
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REQUIREMENTS

23       CONFIG_BPF and bcc.
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OPTIONS

26       -C     Don't clear the screen.
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28       -s SIZE , --datasize SIZE
29              Size of the transmitting buffer (default 256).
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31       -c COUNT, --datacount COUNT
32              Number  of  times ttysnop checks for SIZE bytes of data (default
33              16).
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35       device Either a path to a tty device (eg, /dev/tty0) or  a  pts  number
36              (eg, the "3" from /dev/pts/3).
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EXAMPLES

39       Snoop output from /dev/pts/2
40              # ttysnoop /dev/pts/2
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42       Snoop output from /dev/pts/2 (shortcut)
43              # ttysnoop 2
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45       Snoop output from the system console
46              # ttysnoop /dev/console
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48       Snoop output from /dev/tty0
49              # ttysnoop /dev/tty0
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OVERHEAD

52       As  the  rate  of  tty_write() is expected to be very low (<100/s), the
53       overhead of this tool is expected to be negligible.
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SOURCE

56       This is from bcc.
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58              https://github.com/iovisor/bcc
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60       Also look in the bcc distribution for a  companion  _examples.txt  file
61       containing example usage, output, and commentary for this tool.
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OS

64       Linux
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STABILITY

67       Unstable - in development.
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AUTHOR

70       Brendan Gregg
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