Add support for piping COPY to/from an external program.

This includes backend "COPY TO/FROM PROGRAM '...'" syntax, and corresponding
psql \copy syntax. Like with reading/writing files, the backend version is
superuser-only, and in the psql version, the program is run in the client.

In the passing, the psql \copy STDIN/STDOUT syntax is subtly changed: if you
the stdin/stdout is quoted, it's now interpreted as a filename. For example,
"\copy foo from 'stdin'" now reads from a file called 'stdin', not from
standard input. Before this, there was no way to specify a filename called
stdin, stdout, pstdin or pstdout.

This creates a new function in pgport, wait_result_to_str(), which can
be used to convert the exit status of a process, as returned by wait(3),
to a human-readable string.

Etsuro Fujita, reviewed by Amit Kapila.

1 files changed, 92 insertions, 0 deletions

diff --git a/src/port/wait_error.c b/src/port/wait_error.c
new file mode 100644
index 00000000000..ac9c52b3169
--- /dev/null
+++ b/src/port/wait_error.c
@@ -0,0 +1,92 @@
+/*-------------------------------------------------------------------------
+ *
+ * wait_error.c
+ *		Convert a wait/waitpid(2) result code to a human-readable string
+ *
+ *
+ * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/port/wait_error.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef FRONTEND
+#include "postgres.h"
+#else
+#include "postgres_fe.h"
+#endif
+
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/wait.h>
+
+/*
+ * Return a human-readable string explaining the reason a child process
+ * terminated. The argument is a return code returned by wait(2) or
+ * waitpid(2). The result is a translated, palloc'd or malloc'd string.
+ */
+char *
+wait_result_to_str(int exitstatus)
+{
+	char		str[512];
+	char	   *result;
+
+	if (WIFEXITED(exitstatus))
+	{
+		/*
+		 * Give more specific error message for some common exit codes that
+		 * have a special meaning in shells.
+		 */
+		switch (WEXITSTATUS(exitstatus))
+		{
+			case 126:
+				snprintf(str, sizeof(str), _("command not executable"));
+				break;
+
+			case 127:
+				snprintf(str, sizeof(str), _("command not found"));
+				break;
+
+			default:
+				snprintf(str, sizeof(str),
+						 _("child process exited with exit code %d"),
+						 WEXITSTATUS(exitstatus));
+		}
+	}
+	else if (WIFSIGNALED(exitstatus))
+#if defined(WIN32)
+		snprintf(str, sizeof(str),
+				 _("child process was terminated by exception 0x%X"),
+				 WTERMSIG(exitstatus));
+#elif defined(HAVE_DECL_SYS_SIGLIST) && HAVE_DECL_SYS_SIGLIST
+	{
+		char		str2[256];
+
+		snprintf(str2, sizeof(str2), "%d: %s", WTERMSIG(exitstatus),
+				 WTERMSIG(exitstatus) < NSIG ?
+				 sys_siglist[WTERMSIG(exitstatus)] : "(unknown)");
+		snprintf(str, sizeof(str),
+				 _("child process was terminated by signal %s"), str2);
+	}
+#else
+		snprintf(str, sizeof(str),
+				 _("child process was terminated by signal %d"),
+				 WTERMSIG(exitstatus));
+#endif
+	else
+		snprintf(str, sizeof(str),
+				 _("child process exited with unrecognized status %d"),
+				  exitstatus);
+
+#ifndef FRONTEND
+	result = pstrdup(str);
+#else
+	result = strdup(str);
+#endif
+	return result;
+}