> What a reasonable default is depends on the type of application and how it's likely to be used. No default (other than calling isatty) is reasonable, because

> What a reasonable default is depends on the type of application and how it's likely to be used. No default (other than calling isatty) is reasonable, because you don't know (and you don't want to know) what your output is being piped through. If you really must, add a flag to force enable/disable escape codes. > "prog | grep foo" outputs to the terminal. From prog's perspective it doesn't, but it does. Do you want escape sequences in there? Sometimes you do, sometimes you don't. What happens if "prog" outputs an escape sequence (e.g. set color) on one line, and outputs another one (reset color) a few lines down? grep might match one or the other, or none, or something in the middle. grep might want to output its own escape sequences (like it can do for highlighting a match). "prog" can't know what grep could possibly want to output, without inspecting grep's entire argument line, and effectively re-implementing all of grep - bug-for-bug, compensating for differences in GNU, BSD, BusyBox, etc. There is no sane way to handle every edge case here, and you will get frustrated every time you hit one. > Even "prog | less" outputs to the terminal, indirectly, and less can interpret escape sequences. $ echo hello | less > hello.txt $ cat hello.txt hello It can, but should it? http://harmful.cat-v.org/cat-v/ http://harmful.cat-v.org/cat-v/