NAME isatty - determine if file is a teletype/CRT device SYNOPSIS stat = isatty (fd) filedes fd integer stat returned as YES/NO DESCRIPTION This function returns YES if the file specified by 'fd' is a teletype-like device, otherwise it returns NO. 'Fd' is a file descriptor returned by a call to open or create. IMPLEMENTATION When a file is opened, a flag is usually set indicating what device the file is associated with. This function generally reads that flag. Other implementations are possible, depending upon the operating system involved. 'Isatty' is generally used by the tools to determine whether they should issue prompts or not. SEE ALSO open, create DIAGNOSTICS NO is returned if 'fd' is in error.