diff --git a/CHANGES b/CHANGES
index ae8ab5a..778677a 100644
--- a/CHANGES
+++ b/CHANGES
@@ -21,6 +21,8 @@ corrections:
 	corrected some bugs and typos in doc/socat.yo, EXAMPLES, C comments
 
 further changes:
+	procan -c prints C defines important for socat
+
 	added test OPENSSLEOF for OpenSSL half close
 
 ####################### V 1.6.0.0:
diff --git a/Makefile.in b/Makefile.in
index 335caf9..100e390 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -1,5 +1,5 @@
 # source: Makefile.in
-# Copyright Gerhard Rieger 2001-2007
+# Copyright Gerhard Rieger 2001-2008
 # Published under the GNU General Public License V.2, see file COPYING
 
 # note: @...@ forms are filled in by configure script
@@ -50,7 +50,7 @@ XIOSRCS = xioinitialize.c xiohelp.c xioparam.c xiodiag.c xioopen.c xioopts.c \
 	xio-pty.c xio-openssl.c \
 	xio-ascii.c xiolockfile.c xio-tcpwrap.c xio-ext2.c xio-tun.c
 XIOOBJS = $(XIOSRCS:.c=.o)
-UTLSRCS = error.c dalan.c procan.c hostan.c fdname.c sysutils.c utils.c nestlex.c @FILAN@ @SYCLS@ @SSLCLS@
+UTLSRCS = error.c dalan.c procan.c procan-cdefs.c hostan.c fdname.c sysutils.c utils.c nestlex.c @FILAN@ @SYCLS@ @SSLCLS@
 UTLOBJS = $(UTLSRCS:.c=.o)
 CFILES = $(XIOSRCS) $(UTLSRCS) socat.c procan_main.c filan_main.c
 OFILES = $(CFILES:.c=.o)
@@ -107,7 +107,7 @@ depend: $(CFILES) $(HFILES)
 socat: socat.o libxio.a
 	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ socat.o libxio.a $(CLIBS)
 
-PROCAN_OBJS=procan_main.o procan.o hostan.o error.o sycls.o sysutils.o utils.o
+PROCAN_OBJS=procan_main.o procan.o procan-cdefs.o hostan.o error.o sycls.o sysutils.o utils.o
 procan: $(PROCAN_OBJS)
 	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $(PROCAN_OBJS) $(CLIBS)
 
diff --git a/procan-cdefs.c b/procan-cdefs.c
new file mode 100644
index 0000000..039a682
--- /dev/null
+++ b/procan-cdefs.c
@@ -0,0 +1,84 @@
+/* source: procan.c */
+/* Copyright Gerhard Rieger 2008 */
+/* Published under the GNU General Public License V.2, see file COPYING */
+
+/* a function that prints compile time parameters */
+/* the set of parameters is only a small subset of the available defines and
+   will be extended on demand */
+
+
+#include "xiosysincludes.h"
+#include "mytypes.h"
+#include "compat.h"
+#include "error.h"
+
+#include "procan.h"
+
+int procan_cdefs(FILE *outfile) {
+   /* basic C/system constants */
+#ifdef FD_SETSIZE
+   fprintf(outfile, "#define FD_SETSIZE %u\n", FD_SETSIZE);
+#endif
+#ifdef NFDBITS
+   fprintf(outfile, "#define NFDBITS %u\n", NFDBITS);
+#endif
+#ifdef O_RDONLY
+   fprintf(outfile, "#define O_RDONLY %u\n", O_RDONLY);
+#endif
+#ifdef O_WRONLY
+   fprintf(outfile, "#define O_WRONLY %u\n", O_WRONLY);
+#endif
+#ifdef O_RDWR
+   fprintf(outfile, "#define O_RDWR %u\n", O_RDWR);
+#endif
+#ifdef SHUT_RD
+   fprintf(outfile, "#define SHUT_RD %u\n", SHUT_RD);
+#endif
+#ifdef SHUT_WR
+   fprintf(outfile, "#define SHUT_WR %u\n", SHUT_WR);
+#endif
+#ifdef SHUT_RDWR
+   fprintf(outfile, "#define SHUT_RDWR %u\n", SHUT_RDWR);
+#endif
+
+   /* termios constants */
+#ifdef CRDLY
+   fprintf(outfile, "#define CRDLY 0%011o\n", CRDLY);
+#endif
+#ifdef CR0
+   fprintf(outfile, "#define CR0 0%011o\n", CR0);
+#endif
+#ifdef CR1
+   fprintf(outfile, "#define CR1 0%011o\n", CR1);
+#endif
+#ifdef CR2
+   fprintf(outfile, "#define CR2 0%011o\n", CR2);
+#endif
+#ifdef CR3
+   fprintf(outfile, "#define CR3 0%011o\n", CR3);
+#endif
+#ifdef TABDLY
+   fprintf(outfile, "#define TABDLY 0%011o\n", TABDLY);
+#endif
+#ifdef TAB0
+   fprintf(outfile, "#define TAB0 0%011o\n", TAB0);
+#endif
+#ifdef TAB1
+   fprintf(outfile, "#define TAB1 0%011o\n", TAB1);
+#endif
+#ifdef TAB2
+   fprintf(outfile, "#define TAB2 0%011o\n", TAB2);
+#endif
+#ifdef TAB3
+   fprintf(outfile, "#define TAB3 0%011o\n", TAB3);
+#endif
+#ifdef CSIZE
+   fprintf(outfile, "#define CSIZE 0%011o\n", CSIZE);
+#endif
+
+   /* stdio constants */
+#ifdef FOPEN_MAX
+   fprintf(outfile, "#define FOPEN_MAX %u\n", FOPEN_MAX);
+#endif
+   return 0;
+}
diff --git a/procan.h b/procan.h
index 9a68c0c..4fd8e06 100644
--- a/procan.h
+++ b/procan.h
@@ -1,10 +1,11 @@
 /* source: procan.h */
-/* Copyright Gerhard Rieger 2001 */
+/* Copyright Gerhard Rieger 2001-2008 */
 /* Published under the GNU General Public License V.2, see file COPYING */
 
 #ifndef __procan_h_included
 #define __procan_h_included 1
 
 extern int procan(FILE *outfile);
+extern int procan_cdefs(FILE *outfile);
 
 #endif /* !defined(__procan_h_included) */
diff --git a/procan_main.c b/procan_main.c
index ed6390a..699c05c 100644
--- a/procan_main.c
+++ b/procan_main.c
@@ -32,6 +32,7 @@ int main(int argc, const char *argv[]) {
 #if WITH_HELP
       case '?': case 'h': procan_usage(stdout); exit(0);
 #endif /* WITH_HELP */
+      case 'c': procan_cdefs(stdout); exit(0);
 #if LATER
       case 'V': procan_version(stdout); exit(0);
       case 'l': diag_set(arg1[0][2], &arg1[0][3]); break;
@@ -79,6 +80,7 @@ static void procan_usage(FILE *fd) {
 #if WITH_HELP
    fputs("      -?|-h  print a help text describing command line options\n", fd);
 #endif
+   fputs("      -c     print values of compile time C defines\n", fd);
 #if LATER
    fputs("      -d     increase verbosity (use up to 4 times; 2 are recommended)\n", fd);
 #endif