Erlang build on Linux

Samuel Tardieu <>
Thu Nov 25 13:18:14 CET 1999

| FYI, it built fine on my Debian 2.0 (slink) machine with gcc

Yes, but you built it my hand, not as a Debian package (which gives the beam
compiler a non-tty FD as input and a tty FD as output).

The culprit seems to be in erts/emulator/sys/unix/sys.c. In start_cat(),
the following piece of code loops unendlessly when connected to /dev/null:

	 * Copy standard input to standard output.
	for (;;) {
	    char sbuf[1024];
	    int n;
	    int written;
	    char *s;

	    n = read(0, sbuf, sizeof(sbuf));
	    if (n == -1 && (errno == ERRNO_BLOCK || errno == EINTR)) {

0 is a descriptor in non-blocking mode. When there is nothing to read, read()
returns -1 with errno equal to EAGAIN (== ERRNO_BLOCK), thus provoking a loop.

I haven't read this code carefully, but I must admit that I am quite surprised
at this time.

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