err¶

write an error message to the console, never to stdout
NAME
    err - write an error message to the console, never to stdout
          (//#use err)

SYNOPSIS
    //#use err          cc splices /lib/lib_err.c

DESCRIPTION
    eputs(s) writes an error message to the CONSOLE, bypassing stdout.

    WHY IT EXISTS. The puts() builtin compiles to SYS_PUTS + SYS_PUTC,
    both of which go to *stdout* -- which the shell may have pointed at a
    file or a pipe. So `cat missing >F` used to put "cat: not found"
    INSIDE F, and `cat missing | wc` fed the error text to wc as DATA,
    which counted it and reported a plausible wrong number instead of
    failing. The OS already prints its own `?...` errors through the BIOS
    (always the console); eputs() gives /bin commands the same escape
    hatch, so a diagnostic can never be mistaken for output. Even the
    trailing newline goes to CONOUT ($0103), not SYS_PUTC, so the message
    is never split across two sinks.

CONVENTION
    Use eputs() for anything on a `return 1` (failure) path, INCLUDING a
    usage message printed because the arguments were wrong. Keep plain
    puts() for usage the user explicitly asked for with -h -- that is
    requested output, and `cmd -h >notes.txt` should capture it.

    The asm twins do the same thing inline: `JSR PUTS` + `JSR CONOUT`
    instead of `JSR SYS_PUTS` + `JSR SYS_PUTC`.

SEE ALSO
    abi, cat, grep