pipeln

commit fd350bad9f011b443d27740667c141fc57d2d36e
parent 8432d5ce27e628b0fec22720f57e31665dcd0dd5
Author: Louis Burda <quent.burda@gmail.com>
Date:   Wed,  7 Jun 2023 21:49:17 +0200

Parallelize process execution

Diffstat:
M
main.c
 | 
40
+++++++++++++++++++++++++++-------------

1 file changed, 27 insertions(+), 13 deletions(-)
diff --git a/main.c b/main.c
@@ -1,5 +1,7 @@
-#include <sys/wait.h>
+#include <asm-generic/errno-base.h>
 #include <linux/limits.h>
+#include <sys/wait.h>
+#include <errno.h>
 #include <unistd.h>
 #include <dirent.h>
 #include <wait.h>
@@ -66,10 +68,9 @@ findbin(const char *name)
 	die("findbin %s", name);
 }
 
-int
+void
 run(int *in, int *out, const char **argv)
 {
-	int status;
 	pid_t child;
 
 	if (!argv[0]) die("run: empty command");
@@ -83,26 +84,39 @@ run(int *in, int *out, const char **argv)
 	if (!child) {
 		if (in) {
 			close(0);
-			dup2(in[0], 0);
+			if (dup2(in[0], 0) < 0)
+				die("dup2:");
 		}
 		if (out) {
 			close(1);
-			dup2(out[1], 1);
+			if (dup2(out[1], 1) < 0)
+				die("dup2:");
 		}
 		execv(argv[0], (char *const *) argv);
 		die("execv %s:", argv[0]);
 	}
 	if (in) close(in[0]);
 	if (out) close(out[1]);
+}
 
-	do {
-		waitpid(child, &status, 0);
-	} while (!WIFEXITED(status) && !WIFSIGNALED(status));
+void
+waitall(void)
+{
+	int rc, status, exitcode;
 
-	if (WIFEXITED(status))
-		return WEXITSTATUS(status);
-	else
-		return 128 + WTERMSIG(status);
+	errno = 0;
+	exitcode = 0;
+	do {
+		rc = waitpid(-1, &status, 0);
+		if (rc < 0 && errno != EINTR && errno != ECHILD)
+			die("waitpid:");
+		if (!exitcode && WIFEXITED(status))
+			exitcode = WEXITSTATUS(status);
+		else if (!exitcode && WIFSIGNALED(status))
+			exitcode = WTERMSIG(status);
+	} while (rc >= 0 && errno != ECHILD);
+
+	exit(exitcode);
 }
 
 int
@@ -126,8 +140,8 @@ main(int argc, const char **argv)
 			/* run piped cmd */
 			*arg = NULL;
 			run(in, out, cmdargs);
+			if (!out) waitall();
 			cmdargs = arg + 1;
-			if (!out) break;
 
 			/* out => in */
 			in = out;