[patch] preserve-redirections.patch

preserve-redirections.patch (text/plain), 3.25 KB, created by Alexandr Tiurin on 2011-09-03 04:27:14 UTC

--- SOURCES/tcl-snmptools-1.0/generic/util.c	2008-01-29 01:09:38.000000000 -0800
+++ BUILD/tcl-snmptools-1.0/generic/util.c	2009-06-18 21:53:50.000000000 -0700
@@ -23,6 +23,11 @@
 #include <errno.h> // errno
 #include <stdlib.h> // free
 
+#ifndef WIN32
+#include <unistd.h> // dup, dup2, close
+#include <fcntl.h> // fcntl, F_GETFD, F_SETFD
+#endif
+
 #include "util.h"
 
 #define BUFLEN 500
@@ -55,11 +60,31 @@
  * we have many interpreters (with different PID), so the
  * thread-safe issue doesn't come up as well.
  */
+/*
+ * As originally implemented, this technique grossly violates
+ * the Principle of Least Astonishment on Unix by destroying 
+ * the output redirections of any TCL program that uses tcl-snmptools.
+ * Therefore we attempt to preserve the original stdout/stderr.
+ */
+#ifndef WIN32
+static int stdout_fd, stderr_fd;
+static fpos_t stdout_pos, stderr_pos;
+static long stdout_flags, stderr_flags;
+#endif
+
 char *captureOutput(void) {
     extern char *tempfile;
     FILE *fd;
     tempfile = tempnam(TMP, "TEMP");
 
+#ifndef WIN32
+    /* preserve the original stdout */
+    fflush(stdout);
+    fgetpos(stdout, &stdout_pos);
+    stdout_flags = fcntl(fileno(stdout), F_GETFD);
+    stdout_fd = dup(fileno(stdout));
+#endif
+
     fd = freopen(tempfile, "a", stdout);
     if(fd == NULL) {
         printres("%s", strerror(errno));
@@ -68,6 +93,14 @@
     }
     setvbuf(fd, (char *) NULL, _IONBF, 0);
 
+#ifndef WIN32
+    /* preserve the original stderr */
+    fflush(stderr);
+    fgetpos(stderr, &stderr_pos);
+    stderr_flags = fcntl(fileno(stderr), F_GETFD);
+    stderr_fd = dup(fileno(stderr));
+#endif
+
     fd = freopen(tempfile, "a", stderr);
     if(fd == NULL) {
         printres("%s", strerror(errno));
@@ -83,6 +116,7 @@
 int restoreOutput(char *tempfile) {
     int errors = 0;
 
+#ifdef WIN32
     /* Ignore errors but include in the output and return value */
     if(freopen(TTY, "w", stdout) == NULL) {
         errors++; 
@@ -92,6 +126,24 @@
         errors++;
         printres("%s", strerror(errno));
     }
+#else
+    /* restore the original stdout */
+    fflush(stdout);
+    dup2(stdout_fd, fileno(stdout));
+    fcntl(fileno(stdout), F_SETFD, stdout_flags);
+    close(stdout_fd);
+    clearerr(stdout);
+    fsetpos(stdout, &stdout_pos);
+
+    
+    /* restore the original stderr */
+    fflush(stderr);
+    dup2(stderr_fd, fileno(stderr));
+    fcntl(fileno(stderr), F_SETFD, stderr_flags);
+    close(stderr_fd);
+    clearerr(stderr);
+    fsetpos(stderr, &stderr_pos);
+#endif
 
     if(remove(tempfile)) {
         errors++;
@@ -106,6 +158,7 @@
     FILE *fd;
     int errors = 0;
 
+#ifdef WIN32
     /* Ignore errors but include in the output and return value */
     if(freopen(TTY, "w", stdout) == NULL) {
         errors++; 
@@ -115,6 +168,21 @@
         errors++;
         printres("%s", strerror(errno));
     }
+#else
+    /* restore the original stdout */
+    fflush(stdout);
+    dup2(stdout_fd, fileno(stdout));
+    close(stdout_fd);
+    clearerr(stdout);
+    fsetpos(stdout, &stdout_pos);
+    
+    /* restore the original stderr */
+    fflush(stderr);
+    dup2(stderr_fd, fileno(stderr));
+    close(stderr_fd);
+    clearerr(stderr);
+    fsetpos(stderr, &stderr_pos);
+#endif
 
     fd = fopen(tempfile, "r");
     if(fd == NULL) {