From e0b2bcda976eb43b3976b750ce4261db6d608af8 Mon Sep 17 00:00:00 2001
From: Joey Hess <joey@gnu.kitenet.net>
Date: Sat, 31 Oct 2009 10:20:08 -0400
Subject: [PATCH] parallel: Allow running independent commands, like `parallel
 -j3 -- ls df "echo hi"`

---
 debian/changelog |  2 ++
 parallel.c       | 44 +++++++++++++++++++++++++++++---------------
 parallel.docbook | 21 +++++++++++++++++++--
 3 files changed, 50 insertions(+), 17 deletions(-)

diff --git a/debian/changelog b/debian/changelog
index 548d301..00fc011 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -2,6 +2,8 @@ moreutils (0.38) UNRELEASED; urgency=low
 
   * Description improvements. Closes: #549450
     (Thanks, Justin B Rye)
+  * parallel: Allow running independent commands,
+    like `parallel -j3 -- ls df "echo hi"`
 
  -- Joey Hess <joeyh@debian.org>  Mon, 05 Oct 2009 13:33:07 -0400
 
diff --git a/parallel.c b/parallel.c
index 99a9727..2358470 100644
--- a/parallel.c
+++ b/parallel.c
@@ -33,8 +33,9 @@
 #include <unistd.h>
 
 void usage() {
-	printf("parallel [OPTIONS] command -- arguments: for each argument, "
-	       "run command with argument\n");
+	printf("parallel [OPTIONS] command -- arguments\n\tfor each argument, "
+	       "run command with argument, in parallel\n");
+	printf("parallel [OPTIONS] -- commands\n\trun specified commands in parallel\n");
 	exit(1);
 }
 
@@ -49,17 +50,24 @@ void exec_child(char **command, char **arguments, int replace_cb, int nargs) {
 	if (replace_cb == 0)
 		argc++;
 	argv = calloc(sizeof(char*), argc + nargs);
-	for (i = 0; i < argc; i++) {
-		argv[i] = command[i];
-		if (replace_cb && (strcmp(argv[i], "{}") == 0))
-			argv[i] = arguments[0];
+	if (command[0]) {
+		for (i = 0; i < argc; i++) {
+			argv[i] = command[i];
+			if (replace_cb && (strcmp(argv[i], "{}") == 0))
+				argv[i] = arguments[0];
+		}
+		if (replace_cb == 0)
+			memcpy(argv + i - 1, arguments, nargs * sizeof(char *));
+		if (fork() == 0) {
+			/* Child */
+			execvp(argv[0], argv);
+			exit(1);
+		}
 	}
-	if (replace_cb == 0)
-		memcpy(argv + i - 1, arguments, nargs * sizeof(char *));
-	if (fork() == 0) {
-		/* Child */
-		execvp(argv[0], argv);
-		exit(1);
+	else {
+		if (fork() == 0) {
+			exit(system(arguments[0]));
+		}
 	}
 	return;
 }
@@ -92,7 +100,8 @@ int main(int argc, char **argv) {
 	int replace_cb = 0;
 	char *t;
 
-	while ((opt = getopt(argc, argv, "+hij:l:n:")) != -1) {
+	while ((argv[optind] && strcmp(argv[optind], "--") != 0) &&
+	       (opt = getopt(argc, argv, "+hij:l:n:")) != -1) {
 		switch (opt) {
 		case 'h':
 			usage();
@@ -132,7 +141,7 @@ int main(int argc, char **argv) {
 			break;
 		}
 	}
-
+	
 	if (replace_cb && argsatonce > 1) {
 		fprintf(stderr, "options -i and -n are incomaptible\n");
 		exit(2);
@@ -146,7 +155,7 @@ int main(int argc, char **argv) {
 		maxjobs = 1;
 #endif
 	}
-
+	
 	while (optind < argc) {
 		if (strcmp(argv[optind], "--") == 0) {
 			int i;
@@ -170,6 +179,11 @@ int main(int argc, char **argv) {
 		optind++;
 	}
 
+	if (argsatonce > 1 && ! command[0]) {
+		fprintf(stderr, "option -n cannot be used without a command\n");
+		exit(2);
+	}
+
 	while (argidx < arglen) {
 		double load;
 
diff --git a/parallel.docbook b/parallel.docbook
index 046bb6c..b09350d 100644
--- a/parallel.docbook
+++ b/parallel.docbook
@@ -37,8 +37,14 @@ Written by Joey Hess
 			<command>parallel</command>
 			<arg>options</arg>
 			<arg>command</arg>
-			<arg>--</arg>
-			<arg>arguments</arg>
+			<command>--</command>
+			<arg>argument ...</arg>
+		</cmdsynopsis>
+		<cmdsynopsis>
+			<command>parallel</command>
+			<arg>options</arg>
+			<command>--</command>
+			<arg>command ...</arg>
 		</cmdsynopsis>
 	</refsynopsisdiv>
 	
@@ -50,6 +56,9 @@ Written by Joey Hess
 		repeated for each argument. Jobs may be run in
 		parallel. The default is to run one job per CPU.</para>
 
+		<para>If no command is specified before the --,
+		the commands after it are instead run in parallel.</para>
+
 	</refsect1>
 	
 	<refsect1>
@@ -122,6 +131,14 @@ Written by Joey Hess
 	<para>This runs three ufraw processes at the same time until
 	all of the NEF files have been processed.
 	</para>
+	
+	<para>
+	<cmdsynopsis>
+		<command>parallel -j 3 -- ls df "echo hi"</command>
+	</cmdsynopsis>
+	</para>
+
+	<para>This runs three independent commands in parallel.</para>
 
 	</refsect1>
 
-- 
2.39.5