NAME

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

SYNOPSIS

       ttysnoop [-h] [-C] device

DESCRIPTION

       ttysnoop watches a tty or pts device, and prints the same output that is appearing on that
       device. It can be used to mirror the output from a shell session, or the system console.

       This works by use of kernel dynamic tracing of the tty_write() function.  This  tool  will
       need updating in case that kernel function changes in a future kernel version.

       Since this uses BPF, only the root user can use this tool.

REQUIREMENTS

       CONFIG_BPF and bcc.

OPTIONS

       -C     Don't clear the screen.

       -s SIZE , --datasize SIZE
              Size of the transmitting buffer (default 256).

       -c COUNT, --datacount COUNT
              Number of times ttysnop checks for SIZE bytes of data (default 16).

       device Either  a  path  to  a tty device (eg, /dev/tty0) or a pts number (eg, the "3" from
              /dev/pts/3).

EXAMPLES

       Snoop output from /dev/pts/2
              # ttysnoop /dev/pts/2

       Snoop output from /dev/pts/2 (shortcut)
              # ttysnoop 2

       Snoop output from the system console
              # ttysnoop /dev/console

       Snoop output from /dev/tty0
              # ttysnoop /dev/tty0

OVERHEAD

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

SOURCE

       This is from bcc.

              https://github.com/iovisor/bcc

       Also  look  in  the bcc distribution for a companion _examples.txt file containing example
       usage, output, and commentary for this tool.

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Brendan Gregg

SEE ALSO

       opensnoop(1)