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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 | .TH "isatty" 1 "Sun Dec 11 2016" "Version 2.4.0" "fish" \" -*- nroff -*-
.ad l
.nh
.SH NAME
\fBisatty\fP -- test if a file descriptor is a tty\&.
.PP
.SS "Synopsis"
.PP
.nf
\fBisatty\fP [FILE DESCRIPTOR]
.fi
.PP
.SS "Description"
\fCisatty\fP tests if a file descriptor is a tty\&.
.PP
\fCFILE DESCRIPTOR\fP may be either the number of a file descriptor, or one of the strings \fCstdin\fP, \fCstdout\fP, or \fCstderr\fP\&.
.PP
If the specified file descriptor is a tty, the exit status of the command is zero\&. Otherwise, the exit status is non-zero\&. No messages are printed to standard error\&.
.SS "Examples"
From an interactive shell, the commands below exit with a return value of zero:
.PP
.PP
.nf
\fBisatty\fP
\fBisatty\fP stdout
\fBisatty\fP 2
\fBecho\fP | \fBisatty\fP 1
.fi
.PP
.PP
And these will exit non-zero:
.PP
.PP
.nf
\fBecho\fP | \fBisatty\fP
\fBisatty\fP 9
\fBisatty\fP stdout > file
\fBisatty\fP 2 2> file
.fi
.PP
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