1 files changed, 26 insertions, 0 deletions

diff --git a/lib/maxfd.c b/lib/maxfd.c
new file mode 100644
index 00000000..dcd4d3db
--- /dev/null
+++ b/lib/maxfd.c
@@ -0,0 +1,26 @@
+#include "./maxfd.h"
+#include <errno.h>
+
+long open_max (void) {
+        long maxfd = 0L;
+        /* Try sysconf(_SC_OPEN_MAX) first, as it can be higher than OPEN_MAX.
+         * If that fails and the macro isn't defined, we fall back to an educated
+         * guess. There's no guarantee that our guess is adequate and the program
+         * will die with SIGSEGV if it isn't and the upper boundary is breached. */
+
+#ifdef _SC_OPEN_MAX
+        errno = 0;
+        if ((maxfd = sysconf (_SC_OPEN_MAX)) < 0) {
+                if (errno == 0)
+                        maxfd = DEFAULT_MAXFD;   /* it's indeterminate */
+                else
+                        die (STATE_UNKNOWN, _("sysconf error for _SC_OPEN_MAX\n"));
+        }
+#elif defined(OPEN_MAX)
+        return OPEN_MAX
+#else   /* sysconf macro unavailable, so guess (may be wildly inaccurate) */
+        return DEFAULT_MAXFD;
+#endif
+
+        return(maxfd);
+}