\section isatty isatty - test if the specified file descriptor is a tty \subsection isatty-synopsis Synopsis <tt>isatty [FILE DESCRIPTOR]</tt> \subsection isatty-description Description <tt>isatty</tt> tests if a file descriptor is a tty. <tt>FILE DESCRIPTOR</tt> may be either the number of a file descriptor, or one of the strings <tt>stdin</tt>, \c stdout and <tt>stderr</tt>. If the specified file descriptor is a tty, the exit status of the command is zero. Otherwise, it is non-zero.