Detecting the output stream type of a shell script

Question

I\'m writing a shell script that uses ANSI color characters on the command line.

Example: example.sh

#!/bin/tcsh
printf \"\\033[31m Succ         


        

Answer 1

Inside a bourne shell script (sh, bask, ksh, ...), you can feed the standard output to the tty program (standard in Unix) which tells you whether its input is a tty or not, by using the -s flag.

Put the following into "check-tty":

    #! /bin/sh
    if tty -s <&1; then
      echo "Output is a tty"
    else
      echo "Output is not a tty"
    fi

And try it:

    % ./check-tty
    Output is a tty
    % ./check-tty | cat
    Output is not a tty

I don't use tcsh, but there must be a way to redirect your standard output to tty's standard input. If not, use

    sh -c "tty -s <&1"

as your test command in your tcsh script, check its exit status and you're done.