From 0f012c74fcfaea8d661a729fd5cc2ad4f3563115 Mon Sep 17 00:00:00 2001
From: Tollef Fog Heen <tfheen@err.no>
Date: Tue, 30 Jun 2009 04:19:07 +0200
Subject: [PATCH] Add initial writeup of parallel tool

---
 parallel.c | 144 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 144 insertions(+)
 create mode 100644 parallel.c

diff --git a/parallel.c b/parallel.c
new file mode 100644
index 0000000..09588d6
--- /dev/null
+++ b/parallel.c
@@ -0,0 +1,144 @@
+
+/*
+ *  parallel.c - run commands in parallel until you run out of commands
+ *
+ *  Copyright © 2008  Tollef Fog Heen <tfheen@err.no>
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  version 2 as published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+ * USA
+ *
+ */
+
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <string.h>
+#include <stdio.h>
+#include <sys/time.h>
+#include <time.h>
+#include <stdlib.h>
+#include <sys/select.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+void usage()
+{
+	printf("parallel [OPTIONS] command -- arguments: for each argument,"
+	       "run command with argument\n");
+	exit(1);
+}
+
+void exec_child(char **command, char *argument)
+{
+	char **argv;
+	int argc = 0;
+	int i;
+
+	while (command[argc] != 0) {
+		argc++;
+	}
+	argc++;
+	argv = calloc(sizeof(char*), argc+1);
+	for (i = 0; i < argc; i++) {
+		argv[i] = command[i];
+	}
+	argv[i-1] = argument;
+	if (fork() == 0) {
+		/* Child */
+		execvp(argv[0], argv);
+		exit(1);
+	}
+	return;
+}
+
+int main(int argc, char **argv)
+{
+	int maxjobs = -1;
+	int curjobs = 0;
+	int maxload = -1;
+	int opt;
+	char **command = calloc(sizeof(char*), argc);
+	char **arguments;
+	int argidx = 0;
+	int cidx = 0;
+
+	while ((opt = getopt(argc, argv, "+hj:l:")) != -1) {
+		switch (opt) {
+		case 'h':
+			usage();
+			break;
+		case 'j':
+			maxjobs = atoi(optarg);
+			break;
+		case 'l':
+			maxload = atoi(optarg);
+			break;
+		default: /* ’?’ */
+			usage();
+			break;
+		}
+	}
+
+	if (maxjobs < 0) {
+		usage();
+	}
+
+	while (optind < argc) {
+		if (strcmp(argv[optind], "--") == 0) {
+			int i;
+			size_t mem = (sizeof (char*)) * (argc - optind);
+
+			arguments = malloc(mem);
+			if (! arguments) {
+				exit(1);
+			}
+			memset(arguments, 0, mem);
+			optind++; /* Skip the -- separator, skip after
+				   * malloc so we have a trailing
+				   * null */
+
+			for (i = 0; i < argc - optind; i++) {
+				arguments[i] = strdup(argv[optind + i]);
+			}
+			optind += i;
+		} else {
+			command[cidx] = strdup(argv[optind]);
+			cidx++;
+		}
+		optind++;
+	}
+
+	while (arguments[argidx] != 0) {
+		if (maxjobs > 0 && curjobs < maxjobs) {
+			exec_child(command, arguments[argidx]);
+			argidx++;
+			curjobs++;
+		}
+
+		if (maxjobs > 0 && curjobs == maxjobs) {
+			id_t id_ignored;
+			siginfo_t infop_ignored;
+			waitid(P_ALL, id_ignored, &infop_ignored, WEXITED);
+			curjobs--;
+		}
+	}
+	while (curjobs > 0) {
+		id_t id_ignored;
+		siginfo_t infop_ignored;
+		waitid(P_ALL, id_ignored, &infop_ignored, WEXITED);
+		curjobs--;
+	}
+
+	return 0;
+}
+
-- 
2.39.5