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.\" |
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.\" |
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.\" $FreeBSD$ |
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.\" $FreeBSD$ |
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.\" |
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.\" |
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.Dd November 5, 2008 |
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.Dd October 1, 2021 |
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.Dt SNP 4 |
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.Dt SNP 4 |
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.Os |
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.Os |
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.Sh NAME |
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.Sh NAME |
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.Fn ioctl fd FIONREAD &result |
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.Fn ioctl fd FIONREAD &result |
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.Sh DESCRIPTION |
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.Sh DESCRIPTION |
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.Pa /dev/snp |
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.Pa /dev/snp |
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is a snoop device which allows users to attach to any tty |
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is a snoop device which allows users to attach to any egress tty |
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.Pq a tty that originates from the host |
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and watch activities on it. |
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and watch activities on it. |
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The kernel must be compiled with |
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The kernel must be compiled with |
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.Cd "device snp" , |
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.Cd "device snp" , |
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or the |
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or the |
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the open
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.Nm |
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.Nm |
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device. |
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device. |
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.Pp |
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.Pp |
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The |
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If the |
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.Dv FIONREAD |
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ioctl returns a positive value equal to the number of characters |
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in a read buffer. |
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Special values defined are: |
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.Bl -tag -width ".Dv SNP_TTYCLOSE" |
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.It Dv SNP_OFLOW |
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device overflow occurred, device detached. |
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.It Dv SNP_TTYCLOSE |
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tty not attached. |
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.It Dv SNP_DETACH |
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.Nm |
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.Nm |
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device has been detached by user or tty device has been closed |
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device disappears, closes, or detaches, calls to |
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and detached. |
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.Xr read 2 |
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.El |
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return |
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.Dv EIO |
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and |
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.Xr write 2 |
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return |
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either |
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.Dv EIO |
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or |
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.Dv ENXIO . |
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.Sh SEE ALSO |
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.Sh SEE ALSO |
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.Xr pty 4 , |
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.Xr pty 4 , |
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.Xr kldload 8 , |
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.Xr kldload 8 , |
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In
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the |
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the |
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.Nm |
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.Nm |
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driver was rewritten to work with the replaced TTY subsystem. |
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driver was rewritten to work with the replaced TTY subsystem. |
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.Pp |
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For previous versions of the driver, |
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.Dv FIONREAD |
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ioctl returned a positive value equal to the number of characters |
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in a read buffer. |
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Special values defined are: |
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.Bl -tag -width ".Dv SNP_TTYCLOSE" |
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.It Dv SNP_OFLOW |
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device overflow occurred, device detached. |
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.It Dv SNP_TTYCLOSE |
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tty not attached. |
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.It Dv SNP_DETACH |
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.Nm |
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device has been detached by user or tty device has been closed |
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and detached. |
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.El |
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These values are no longer used, see BUGS. |
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.Sh AUTHORS |
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.Sh AUTHORS |
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.An -nosplit |
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.An -nosplit |
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The author of the current implementation is |
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The author of the current implementation is |
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does not return proper error codes when calling
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It also does not allow |
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It also does not allow |
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.Dv SNPSTTY |
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.Dv SNPSTTY |
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to detach itself from the TTY. |
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to detach itself from the TTY. |
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.Pp |
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Flow control is not supported. |