rewrote xargs in C; implemented parallelization

rc/bin/xargs

@@ -1,23 +0,0 @@
-#!/bin/rc
-fn usage {
-	echo usage: $0 [-n num] program [arguments]
-	exit usage
-}
-rfork e
-ifs='
-'
-nargs=1
-while(~ $1 -*) {
-	switch($1) {
-	case -n
-		nargs=$2
-		shift 2
-	case *
-		echo bla
-		usage
-	}
-}
-while(x = `{read -n $nargs})
-	$* $x
-if(! ~ $#x 0)
-	$* $x

sys/src/cmd/xargs.c

@@ -0,0 +1,72 @@
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+
+void
+usage(void)
+{
+	fprint(2, "usage: xargs [ -n lines ] [ -p procs ] args ...\n");
+	exits("usage");
+}
+
+void
+dowait(void)
+{
+	while(waitpid() != -1)
+		;
+}
+
+void
+main(int argc, char **argv)
+{
+	int lines, procs, i, j, run;
+	char **nargv, **args, **p;
+	static Biobuf bp;
+	
+	lines = 10;
+	procs = 1;
+	ARGBEGIN {
+	case 'n': lines = atoi(EARGF(usage())); break;
+	case 'p': procs = atoi(EARGF(usage())); break;
+	default: usage();
+	} ARGEND;
+	if(argc < 1)
+		usage();
+	
+	nargv = malloc(sizeof(char *) * (argc + lines + 1));
+	if(nargv == nil)
+		sysfatal("malloc: %r");
+	memcpy(nargv, argv, sizeof(char *) * argc);
+	args = nargv + argc;
+	if(Binit(&bp, 0, OREAD) < 0)
+		sysfatal("Binit: %r");
+	Blethal(&bp, nil);
+	atexit(dowait);
+	for(j = 0, run = 1; run; j++){
+		if(j >= procs)
+			waitpid();
+		memset(args, 0, sizeof(char *) * (lines + 1));
+		for(i = 0; i < lines; i++)
+			if((args[i] = Brdstr(&bp, '\n', 1)) == nil){
+				if(i == 0)
+					exits(nil);
+				run = 0;
+				break;
+			}
+		switch(fork()){
+		case -1:
+			sysfatal("fork: %r");
+		case 0:
+			exec(*nargv, nargv);
+			if(**nargv != '/' && strncmp(*nargv, "./", 2) != 0 &&
+					strncmp(*nargv, "../", 3) != 0){
+				*nargv = smprint("/bin/%s", *nargv);
+				exec(*nargv, nargv);
+			}
+			sysfatal("exec: %r");
+		}
+		for(p = args; *p; p++)
+			free(*p);
+	}
+	exits(nil);
+}